JPH0117477B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermal recording paper whose main components are a dye precursor and a color developer that develops color when the dye precursor is heated, and provides a thermal recording paper whose blank areas and colored areas are less likely to be degraded by chemicals. It is something to do. Thermosensitive recording paper consists of (1) a substrate coated with carbon or colored dyes and pigments, and an opaque thermofusible substance coated on top of the substrate; the opaque layer becomes transparent when heated, and the colored layer underneath becomes transparent; The method by which an image is formed. (2) A method that uses heat to form a complex between an electron donor and an electron acceptor. (3) There is a method in which a dye precursor such as crystal violet lactone and an acidic color developer such as a phenol compound are dispersed and applied discontinuously, and one or both are dissolved by heating to develop color. Of these, method (3) is used in general facsimile machines, printers, etc. because it is superior overall in terms of image clarity, resolution, image color tone, and problem with dust. The characteristics required for this type of thermal recording paper are as follows:
It goes without saying that it has sensitivity suitable for various uses, as well as white background, long-term stable colored images that do not fade, no residue that forms during recording, and no dust that adheres to the thermal head during recording. (King) There are things you don't do, etc. Good ones can be made that meet many of these requirements, but plasticizers,
The preservation of the image area due to chemicals such as alcohol, acetone, benzene, and xylene (hereinafter referred to as chemical resistance) is poor, and from a practical standpoint, erasers and vinyl chloride bags containing large amounts of plasticizers are If the image comes in contact with the product, or if it is touched with a hand covered with hand cream or hair styling oil, the image will be discolored and the text will become difficult to read. This phenomenon occurs because the lactone ring of the color-forming lactone compound, which is ring-opened with an acidic color developer, is closed in the presence of a plasticizer such as dibutyl phthalate or dioctyl phthalate. It has also been proposed that this phenomenon can be prevented by forming a film to prevent penetration. (JP-A-54-128347, JP-A-54-3549) However, at present, there are many unsatisfactory points such as a large decrease in sensitivity, stagnation, and poor printing performance. The present inventors have arrived at the present invention as a result of extensive research into thermal recording paper that has good print quality, is free from scum and staining, and has little decrease in sensitivity, with the aim of improving chemical resistance. That is, the above
The thermal recording paper of method (3) is overcoated with an aqueous solution of alginate and dried, and the thickness of the dried coating is 0.5 μm or more, preferably 3 to 12 μm, for chemical resistance.
It is better in terms of color development sensitivity. Coating thickness is 0.5μ
If it is thinner than 12μm, the chemical resistance will not be sufficient, and if it is thinner than 12μm.
The thicker the layer, the better the chemical resistance, but the coloring sensitivity tends to decrease. Another great feature of the alginate coating of the present invention is that it does not cause states in facsimiles or printers, and does not impair printability. The inventors of the present invention have tried overcoating many materials, but there is nothing else that satisfies all of the statesking, chemical resistance, and sensitivity.
Alginate was a unique entity. Alginate is a natural polymer electrolyte that exists in brown algae, and there are various molecular weights ranging from small to large, but it was satisfactory in the present invention regardless of the molecular weight. In addition, the types of salts include natural sodium salts, ammonium salts that can be made by post-processing, salts with amines, and metal salts such as aluminum, calcium, and zinc (metal salts are insoluble in water, so ammonia Both methods were effective. Next, the thermal recording paper before overcoating in the present invention will be described. This base thermal recording paper is conventionally known and is composed of dye precursors, color developers, organic and inorganic pigments, binders, surfactants, waxes as melting point laxatives, lubricants, etc. The coating layer is applied to a paper or synthetic resin film base. Representative examples of dye precursors include crystal violet lactone, 3-indolino-3-P-dimethylaminophenyl-6-dimethylaminophthalide, and 3-diethylamino-7.
-Chlorofluorane, 3-diethylamino-7-
Cyclohexylaminofluorane, 3-diethylamino-5-methyl-7-t-butylfluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-P-butylani Linofluorane, 2-
(N-phenyl-N-ethyl)aminofluorane,
3-diethylamino-7-dibenzylaminofluorane, 3-cyclohexylamino-6-chlorofluorane, 3-diethylamino-6-methyl-
7-xylidinofluorane, 2-anilino-3-
Methyl-6-(N-ethyl-P-toluidino)fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-piperidino-6
-Methyl-7-toluidinofluorane, 3-pyrrolidino-6-methyl-7-(P-toluidino)fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-(N-methylcyclohexyl) amino)-6-methyl-7-anilinofluorane, 3-diethylamino-7-(m-trifluoromethylanilino)fluorane, etc.
It is not limited to these. Further, as the color developer in the present invention, for example,
4-phenylphenol, 4-hydroxyacetophenone, 2.2'-dihydroxydiphenyl,
2.2'-methylenebis(4-chlorophenol),
2.2'-methylenebis(4-methyl-6-t-butylphenol), 4.4'-isopropylidenebis(2-methylphenol), 4.4'-ethylenebis(2-methylphenol), 1.1'-bis(4-hydroxy phenyl)cyclohexane, 2.2-bis(4'-hydroxyphenyl)propane, 4.4'-cyclohexylidenebis(2-isopropylphenol), novolac type phenolic resin, 3-5-di-t-butylsalicylic acid, 3 Examples include, but are not limited to, -5-di-α-methylbenzylsalicylic acid, 3-methyl-5-t-butylsalicylic acid, phthalic acid monoanilide paraethoxybenzoic acid, parabenzyloxybenzoic acid, etc. isn't it. or,
When manufacturing thermal paper, dye precursors, color developers,
In addition, additives such as inorganic and organic pigments, binders, surfactants, and waxes are used to prevent residue from adhering to the facsimile head. Known and publicly available pigments are used, but examples of pigments include aluminum hydroxide, heavy and light calcium carbonate, zinc oxide,
Titanium oxide, barium sulfate, silica gel, activated clay, talc, clay, tisane white, kaolinite, calcined kaolinite, diatomaceous earth, synthetic kaolinite, polyolefin grains, polystyrene grains,
There are urea-formalin resin particles, and binders include casein, styrene-maleic anhydride resin, polyvinyl alcohol, modified polyvinyl alcohol, starch, modified starch, and isobutylene.
Maleic anhydride resin, diisobutylene-maleic anhydride resin, polyacrylamide, modified polyacrylamide, carboxymethyl cellulose,
Methyl vinyl ether/maleic acid copolymer, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxy-modified polyethylene, etc. are used. Nonionic and anionic surfactants are used, and amphoteric and cationic surfactants are generally not used because they cause aggregation of the coating solution. In addition, waxes include stearamide, palmitamide, oleic acid amide, lauric acid amide, ethylene bis stearamide, methylene bis stearamide, methylol stearoamide, paraffin wax,
Furthermore, higher alcohols and higher resin acids may also be used. In addition, as a lubricant, calcium stearate,
Those typified by zinc stearate can be used. Hereinafter, it will be explained in more detail with reference to Examples. Example 1 Part A 3-(N-methylcyclohexylamino)-6-methyl-7-anilinofluorane...12g 10% by weight polyvinyl alcohol aqueous solution...18g Water...30g Part B 4.4'-isopropylidene diphenol ...40g Stearamide ...20g 10% by weight polyvinyl alcohol aqueous solution ...90g Water ...50g Pulverize liquids A and B in separate ball mills for 24 hours,
A coating liquid was prepared using the following formulation. Calcium carbonate (manufactured by Shiraishi Kogyo, calcium carbonate
PC)...20g Solution B...60g 10% by weight polyvinyl alcohol aqueous solution...70g Solution A...20g Water...60g The prepared coating solution was applied to a base paper with a basis weight of 48g/ ^m2 , after drying, the amount of coating was 5g/ It was coated to a thickness of m ² and dried at 60°C for 1 minute to prepare heat-sensitive recording paper. Next, a 5% by weight aqueous solution of sodium alginate (trade name: Kelgin RL, LV, MV, manufactured by Kelco) with three different viscosities was overcoated to a dry film thickness of 5 μm, and the resulting chemical-resistant heat-sensitive recording paper After printing with facsimile, add dioctyl phthalate (DOP), ethyl alcohol, and benzene, respectively.
After dropping one drop, changes in uncolored areas and colored areas were observed. For comparison, polyvinyl alcohol (Comparative Example 1), oxidized starch (Comparative Example 2), polyacrylamide (Comparative Example 3), styrene sodium maleate anhydride (Comparative Example 4), and carboxylic acid were used to obtain the same dry film thickness. A similar test was conducted with an overcoat of methyl cellulose (Comparative Example 5). As a result, as shown in Table 1, the product of the present invention
There was no discoloration of the colored areas due to DOP, and no color development of uncolored areas due to ethyl alcohol or benzene. All comparative examples are the opposite.
Colored areas faded due to DOP, uncolored areas turned black with ethyl alcohol and benzene, and colored areas also faded due to blurring of the image. In addition, only the product of the present invention had good states-king by facsimile, and all the comparative examples had poor results.

[Table] ○: No change △: Color developed ×: Discoloration
×○ mark: Example 2 of discoloration due to bleeding in the image area. Sodium alginate (trade name Kelgin LV) was applied to the thermal recording paper base obtained in Example 1 before overcoating so that the dry film thickness was 0.2 μm to 15 μm. Fading of the colored area due to film thickness and DOP (resistance to DOP)
(Resistance to ethyl alcohol) Color development of uncolored areas by ethyl alcohol (ethyl alcohol resistance) and changes in color development sensitivity by facsimile were observed. At the same time, for comparison, polyvinyl alcohol (trade name: KL-318, manufactured by Kuraray Co., Ltd.), which is said to have good film properties, was tested in the same manner, and the results shown in Table 2 were obtained. In other words, sodium alginate is practically 0.5μ
It is better to coat the film in the range of 3 to 12 μm or more in terms of DOP resistance, ethyl alcohol resistance, and coloring sensitivity.The polyvinyl alcohol used for comparison does not cause states king when the film thickness is thin, but has good resistance.
There is no DOP property, no ethyl alcohol resistance, and when the film gets thick, it is not practical due to states king.
Also, there was some DOP seeping into the stake part, so the DOP resistance was not good.

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Claims (1)

[Claims] 1. In the production of thermal recording paper whose main components are (a) a dye precursor and (b) a color developer that develops color from the dye precursor when heated, A thermal recording paper with improved chemical resistance characterized by having an alginate overcoat layer. 2 The thickness of the alginate overcoat layer is
The thermosensitive recording paper according to claim 1, which has a diameter of 0.5 μm or more, preferably 3 to 12 μm.