JPH021036B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material that has improved staking and other recording properties and stability of the background. The heat-sensitive recording medium in the present invention is one that utilizes a color reaction between a normally colorless or light-colored leuco dye and a color developer such as an organic acid or a phenol compound.
Supports compositions whose main components are leuco dyes, organic acids, color developers such as phenolic compounds, and further include polymeric binders, sensitizers, fillers, lubricants, and other auxiliary materials as necessary. It is painted on the body. Such thermal recording media are widely used in facsimile machines, computer terminals, calculator printers, automatic ticket vending machines, medical and industrial measuring instruments, and others. However, when continuous solid black printing is performed on a conventional thermal recording medium using a recording device that has these thermal heads, the head and the surface of the thermal recording medium stick together, causing a staking phenomenon, which impairs the quality of the recorded image. . Furthermore, there were also problems with the whiteness and stability of the background of the heat-sensitive recording material. In order to improve the above drawbacks, clay, talc, calcium carbonate, magnesium carbonate, magnesium hydroxide, aluminum silicate, etc. were added to the heat-sensitive coloring layer.
A method of incorporating an inorganic filler such as magnesium silicate or white carbon, an organic filler such as urea formaldehyde resin or starch particles, or a lubricant,
Attempts have been made to add release agents, coarse inorganic pigments, etc., but sufficient effects have not yet been obtained. The inventors of the present invention have made extensive studies to improve this problem, and have discovered that very excellent quality can be obtained by using resorcinol monobenzoate as a color developer. Many materials are described in various literature regarding color developers such as organic acids and phenol compounds that color normally colorless or light-colored leuco dyes, but 2,2-bis (Hydroxyphenyl)propane (bisphere A) is the most widely used. When this bisphenol A was used as a color developer, there were problems with staking, background stability, etc., as described above. The present inventors have extensively searched for a color developer to replace bisphenol A, and as a result they have arrived at the present invention. The resorcinol monobenzoate used in the present invention is a white crystal with a melting point of 132 to 135°C, and is composed of polyvinyl chloride, polystyrene, cellulose acetate,
It is commercially available as a light stabilizer for polymer compounds such as ethyl cellulose. By using the resorcinol monobenzoate of the present invention as a color developer, staining is prevented, recording properties are improved, and whiteness is high.
Advantages such as improved background stability and the ability to obtain heat-sensitive recording materials with various sensitivities by using in combination with other phenolic color developers, fatty acid amide, and other sensitizers can be obtained. Of course, the resorcinol monobenzoate of the present invention can be used alone as a color developer for heat-sensitive recording materials, but it can also be used for bisphenol A, 4-tert-butylphenol, 4-phenylphenol,
4'-ethylenebis(2-methylphenol), 1,
Phenol compounds such as 1-bis-(4-hydroxyphenyl)cyclohexane, methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate,
p-hydroxybenzoic acid esters such as propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, phenyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, methylbenzyl p-hydroxybenzoate, benzoic acid, salicylic acid,
It is also possible to use organic acids such as gallic acid and metal salts thereof. In particular, the combination with p-hydroxybenzoic acid ester has an excellent sensitizing effect, probably because of their similar structures, and is therefore more preferably used. Examples of the normally colorless or light-colored leuco dye used in the present invention include 3,3-bis-(p-dimethylaminophenyl)-6-dimethylaminophthalide (crystal violet lactone), 3,
3-bis-(p-dimethylaminophenyl)-6-
Triphenylmethane type such as diethylaminophthalide, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7-chloroanilinofluorane, 3-dibutylamino-7
-chloroanilinofluorane, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7
-anilinofluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7 −
Anilinofluorarane, 3-diethylamino-7
-Fluorane compounds such as -m-trifluoromethylanilinofluorane, as well as spiropyran compounds, auramine compounds, rhodamine lactam compounds, phenothiazine compounds, and phenoxazine compounds are known, and one or more compounds may be used in combination. however, the invention is not limited to these representative examples. Furthermore, waxes and aromatic acid esters are used for various purposes such as adjusting the thermal sensitivity of thermal recording media, improving storage stability, improving whiteness, improving writing performance, preventing residue from adhering to thermal heads, preventing pressure build-up, and improving coating properties. derivative,
Metallic soaps, amino-based and phenolic antioxidants, benzophenone-based and benzotriazole-based ultraviolet absorbers, natural or synthetic inorganic powders, starch particles, organic polymer powders such as urea-formaldehyde resin, Various auxiliary agents such as fluorescent dyes, silicone mold retardants, and alkyl fluoride activators can be added. Examples of waxes that can be used include paraffin wax, microcrystalline wax, carnauba wax, polyethylene wax, polypropylene wax, montan acid wax, and higher fatty acid amide. Examples of aromatic airtel derivatives include alkyl benzoate, allyl benzoate, alkyl salicylate, allyl salicylate, monoalkyl terephthalate, dialkyl terephthalate, dialkyl-2-methyl-terephthalate,
Dialkyl-2-methoxy terephthalate, diphenyl terephthalate, dialkyl isophthalate, etc. are used, and like the above-mentioned higher fatty acid amides, they are effective as sensitivity regulators. Calcium stearate as metal soap,
Higher fatty acid metal salts such as zinc stearate and aluminum stearate are used. Inorganic powders include clay, kaolin, talc,
Calcium carbonate, magnesium carbonate, zinc carbonate,
Magnesium oxide, zinc oxide, titanium oxide, aluminum oxide, silicon oxide, magnesium hydroxide, aluminum hydroxide, magnesium alumina hydroxide, magnesium silicate, aluminum silicate, calcium silicate, white carbon, magnesium aluminosilicate, etc. are used. . A binder is also used to bind these composition dispersions to each other and to adhere them onto a support. As the binder, water-soluble polymers are suitable since the coating agent is usually handled as a water-based paint, such as cellulose derivatives such as methyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose, oxidized starch, cationic starch, and hydroxyethyl starch. , starch compounds such as hydroxypropyl starch, phosphoric acid ester starch, carboxymethyl starch, dialhyde starch, polyvinyl alcohol, polyvinylpyrrolidone, casein, gelatin, gum arabic, polyacrylamide, alkali salts of styrene-maleic anhydride copolymer・Ammonium salts, alkali salts of methyl vinyl ether/maleic anhydride copolymer, etc. are used. Furthermore, styrene-butadiene copolymer latex, acrylate emulsion, etc. can also be used. In addition, various waterproofing agents are also used to improve water resistance. The method for forming the heat-sensitive recording material of the present invention is not particularly limited, but generally, a leuco dye, a color developer, and if necessary, a sensitivity regulator, an inorganic powder, etc. are mixed separately or leuco A dispersion is prepared by dispersing a dye and a color developer in water in a combination that does not mix with each other, and the dispersion is further mixed with a binder and other auxiliary agents to prepare a coating solution, which is then applied onto a support. Obtained by applying and drying. Furthermore, the smoothness of the surface of the recording medium can be improved using a surface treatment device such as a calender. Paper, synthetic paper, plastic film, etc. can be used as the support, but paper is usually most often used in terms of cost, suitability for coating, etc. The heat-sensitive recording medium of the present invention does not have the drawback of states king, so it can record for a long time without trouble.
Since it promotes the effect of the sensitizer, the sensitivity is good.
In these respects, the drawbacks of conventional products have been overcome, and it is extremely useful for various recording purposes. Examples will be shown below to more specifically explain the present invention, but the present invention is of course not limited to these. Example 1

A heat-sensitive coating liquid was prepared by mixing and stirring [Table]. This was coated and dried to a dry coating weight of 4 g/m ² on high-quality paper of 50 g/m ² , and then surface-treated with a super calendar to achieve a smoothness of 250 to 350 seconds, and heat-sensitive recording paper was coated. I got it. Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that bisphenol A was used instead of resorcinol monobenzoate. Example 2

A heat-sensitive coating liquid was prepared by mixing and stirring [Table]. This was coated and dried to a dry coating weight of 5 g/m ² on high-quality paper of 50 g/m ² , and then the surface was treated with a super calender to a smoothness of 250 to 350 seconds, and heat-sensitive recording paper was coated. I got it. Comparative Example 2 A thermosensitive recording paper was obtained in the same manner as in Example 2 except that bisphenol A was used instead of resorcinol monobenzoate. Example 3

[Table] Comparative Example 3 A thermosensitive recording paper was obtained in the same manner as in Example 3 except that bisphenol A was used instead of resorcinol monobenzoate. Example 4

[Table] %Aqueous dispersion

[Table] After preparing a heat-sensitive coating liquid by mixing and stirring, Example 2
A thermosensitive recording paper was obtained in the same manner as above. Comparative Example 4 Example 4 except that a bisphenol A/benzyl p-hydroxybenzoate 7/3 mixture was used instead of the resorcinol monobenate/benzyl p-hydroxybenzoate 7/3 mixture in Example 4.
A thermosensitive recording paper was obtained in the same manner as above. Example 5

A heat-sensitive coating liquid was prepared by mixing and stirring [Table]. 50 of this
g/m ² high-quality paper to a dry coating weight of 5.5 g/m ² and dry, then surface-treated with a super calender to a smoothness of 350 to 450 seconds to produce heat-sensitive recording paper. Obtained. Comparative Example 5 In Example 5, bisphenol A/dimethyl terephthalate 6/4 was used instead of the resorcinol monobenzoate/dimethyl terephthalate 6/4 mixture.
A thermosensitive recording paper was obtained in the same manner as in Example 5 except that the mixture of 4 was used. Table 1 shows the evaluation results of the heat-sensitive recording thus obtained. As is clear from the table, in the examples of the present invention, there was almost no occurrence of staining compared to the comparative examples using bisphenol A as a color developer.
The skin is white and there is little skin discoloration due to heat/temperature, providing good properties. In addition, a sensitizing effect by the sensitivity regulator has been observed, and the present invention enables the production of a thermosensitive recording medium having a sensitivity compatible with recording equipment.

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Claims (1)

[Claims] 1. A heat-sensitive recording material containing a colorless or light-colored leuco dye and resorcinol monobenzoate.