JPH0214913B2 - - 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 a sensitivity suitable for various uses, as well as white background, long-term stable colored images that do not fade, no scum generated during recording, and no stains on 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 into 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 be 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, which causes the plasticizer to penetrate onto the thermal recording paper. It has also been proposed that such a phenomenon can be prevented by forming a film to prevent this. (JP-A-54-128347, JP-A-54-3549) In addition, the present inventors have also developed an overcoat agent that has good chemical resistance, printability, and color development sensitivity, and does not cause scum or states king. Special request 1984-
No. 182557, patent application No. 56-981 has been filed. However, conventional chemical-resistant thermal paper has an overcoat only on the heat-sensitive coloring layer, and from a practical standpoint, it is still incomplete as a chemical-resistant thermal paper. It was hot. In other words, the main use of chemical-resistant thermal paper is POS.
It is used as a barcode paper for commercial use, and is attached directly to fresh foods and foods containing a lot of oil wrapped in vinyl chloride film. in this case,
The oil oozes out to the surface through the thin vinyl chloride film, and the oozing oil and plasticizer in the vinyl chloride film penetrate from the back side of the thermal paper and reach the thermosensitive coloring layer, preventing printed barcodes and characters from being printed. It will cause the color to fade. Therefore, it has been found that simply having a chemical-resistant overcoat layer on the front surface of the heat-sensitive coloring layer is insufficient for such uses, and the present invention has been achieved. The structure of the chemical-resistant thermal paper of the present invention is that a layer mainly composed of a water-soluble polymer compound is provided on the front and/or back side of a support, and a dye precursor and a layer are formed on one side of the pretreated support. A heat-sensitive coloring layer containing a color developer as a main component that causes the dye precursor to develop color when heated is provided, and an overcoat layer containing alginate is further provided on top of this heat-sensitive coloring layer. This prevents chemicals from penetrating into the heat-sensitive coloring layer from both the front and back sides. Regarding the materials used and the method for using them, the support may be paper, synthetic paper, or synthetic resin film, but paper is generally used. Water-soluble polymer compounds to be treated on the front and/or back side of the support include casein, polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, starch, modified starch, alkali salts of isobutylene-maleic acid resin, and polyacrylic. Amid,
Modified polyacrylamide, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, methyl vinyl ether/maleic acid copolymer, hydroxypropyl cellulose, carboxyl-modified polyethylene, alkali salt of styrene/maleic acid resin, alginate, dextrin, etc. alone or in combination. More than one species is used in combination. However, the present invention is not limited to these, and any water-soluble polymer is effective. Further, various water-resistant agents, water repellents, antifoaming agents, etc. may be added to these water-soluble polymer compounds as additives. The present inventors treated the front and/or back side of the support with a water-insoluble polymer compound to perform a penetration prevention test for plasticizers, rapeseed oil, etc., but none of them were as good as the water-soluble polymer compound. I stopped talking. For example, in styrene-butadiene rubber, the back side of the support is
Even with a coating of 10 g/m ³ , there was migration of the plasticizer even to the heat-sensitive layer on the surface of the support, causing the coloring of the heat-sensitive layer to fade. The water-soluble polymer compound of the present invention may be applied to the support in an amount of about 2 to 5 g/m ³ , and the treatment methods include coating the back side of the support and coating the support with a heat-sensitive layer. Methods include applying an undercoat beforehand, coating both sides of the support, or size pressing. Next, regarding the materials for the thermosensitive coloring layer, representative examples of dye precursors include crystal violet lactone, 3-indolino-3-P-
Dimethylaminophenyl-6-dimethylaminophthalide, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-cyclohexylaminofluorane, 3-diethylamino-5-methyl-7-t-butylfluorane, 3 -diethylamino-6-methyl-7-anilinofluorane,
3-diethylamino-6-methyl-7-P-butylanilinofluorane, 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)fluoran, 3-
Piperidino-6-methyl-7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-7-(m-trifluoromethylanilino) Examples include, but are not limited to, fluoran. 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-hydroxyphenyl)-cyclohexane,
2,2-bis(4'-hydroxyphenyl)propane, 4,4'-cyclohexylidenebis(2-isopropylphenol), novolac type phenol resin, 3-5-di-t- Butyl salicylic 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, and parabenzyloxybenzoic acid. . In addition, when manufacturing thermal paper, in addition to dye precursors and color developers, inorganic and organic pigments and binders, other surfactants, and waxes are added to prevent residue from adhering to the facsimile head. agent is used. 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, satin white, kaolinite, calcined kaolinite, diatomaceous earth, synthetic kaolinite, polyolefin grains, polystyrene grains,
There are urea-formalin resin particles, etc., and binders include casein, styrene-maleic anhydride resin, polyvinyl alcohol, modified polyvinyl alcohol, starch, modified starch, 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,
Alcohols, higher resin acids may also be used. In addition, as a lubricant, calcium stearate,
Those typified by zinc stearate can be used. Next, we will discuss the material for the overcoat layer that is coated on top of the heat-sensitive coloring layer. The overcoat layer of the present invention contains alginate. In particular, it is preferable that the overcoat layer has an alginate as a main component, or an alginate and a water-soluble polymer compound other than the alginate as a main component. It is more preferable to use at least one of hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol as the water-soluble polymer compound other than alginate. Furthermore, various additives such as a water resistant agent, a water repellent, an antifoaming agent, etc. may be added to these overcoating agents. In addition to the above-mentioned overcoating agents, the present inventors have investigated various water-soluble polymer compounds, and some of them have good chemical resistance, but when printed with a heat-sensitive facsimile or thermal printer, they cause a staking phenomenon. In many cases, the overcoat agent stuck to the head and caused printing problems. The thickness of the dry film of the overcoat agent in the present invention is 0.5 μm or more, preferably 3 to 12 μm, which is better in terms of chemical resistance and coloring sensitivity. If the film thickness is less than 0.5 μm, chemical resistance will not be sufficient.
Further, if the thickness is more than 12 μm, chemical resistance is good, but color development sensitivity tends to decrease. Examples will be described in more detail below. Examples 1 to 3 relate to the pretreated support before applying the heat-sensitive layer, Example 4 relates to the heat-sensitive layer, and Example 5 relates to the overcoat agent after applying the heat-sensitive layer. be. The results obtained by combining these are summarized in Table 1. The evaluation method was as follows. Chemical resistance: The optical density of the resulting thermal paper is 1.20 using a facsimile.
After developing color, 10 sheets of commercially available soft vinyl chloride film (Shin-Etsu Lap) were layered on the back side, and 60
A load of g/cm ³ was applied and the sample was allowed to stand at 40° C. for 72 hours, and the change in color density (optical density) on the table was shown as the residual rate of density. After coloring thermal paper made in the same manner as above to an optical density of 1.20 using a facsimile, a light vinyl chloride film was applied to the surface (overcoated surface).
Ten sheets were stacked and treated under the same conditions to show the remaining density. Example 1 Polyvinyl alcohol (Kuraray ^PVA-
105), ○ Sodium alginate, ○ Starch halide (MS-3800), ○ Dimethyl cellulose (Shin-Etsu Chemical Metrose SM-15), ○ Hydroxyethyl cellulose (Fuji Chemical Co., Ltd. AL-15), ○ Hestylene butadiene rubber (Nippon Zeon MX-1029) Comparative Example 1 was applied to a dry coating amount of 5 g/m ³ (comparative example 2 is the case where nothing was applied), and Example 4 was applied on this coated surface. Example 5
An overcoat layer was provided. Example 2 The heat-sensitive layer of Example 4 was provided on the unpretreated side of the pretreated support obtained in Example 1, and the overcoat layer of Example 5 was further provided thereon. Comparative Example 3 is used when the pretreatment agent is styrene-butadiene rubber. Example 3 Aqueous solutions from ○I to ○ in Example 1 were applied to high-quality paper with a basis weight of 52 g/m ³ and a Steckigt size degree of 3 seconds using a size press method, from both sides of the paper, with a dry coating amount of 3 g/m ² , and the heat-sensitive layer of Example 4 was provided on one side of this pretreated support, and the overcoat layer of Example 5 was further provided thereon. The case of styrene-butadiene rubber (○) is referred to as Comparative Example 4. Example 4 Liquid A 3-(N-methyl-N-cyclohexylamino)
-6-methyl-7-anilinofluorane
...12g 10% by weight polyvinyl alcohol aqueous solution ...18g Water ...30g Solution B 4,4'-isopropylidene diphenol
...40g Stearamide ...20g 10 weight polyvinyl alcohol aqueous solution ...90g Water ...50g Liquids A and B were ground and dispersed in separate ball mills for 24 hours, and a coating liquid was prepared using the following formulation. Calcium carbonate Manufactured by Shiroishi Industries, 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 the various supports of Examples 1 to 3 at a dry coating amount of 5g/m ³ to obtain an overcoat support in Example 5 below. Example 5 No overcoat agent... Comparative Example 5 Styrene-butadiene rubber (manufactured by Nippon Zeon,
TX-1007) Comparative Example 6 Sodium alginate, 1:1 mixture of sodium alginate/hydroxyethylcellulose, 1:1 mixture of sodium alginate/methylcellulose, 1:1 mixture of sodium alginate/carboxymethylcellulose, 1:1 mixture of sodium alginate/polyvinyl alcohol was applied onto the heat-sensitive layer of the thermal paper obtained in Examples 1 to 3 and Example 4 to a dry thickness of 4 μm to obtain a final chemical-resistant thermal paper.

【table】

[Table] The upper row of numerical values is the residual rate of color density when the vinyl chloride film is layered on the surface of the overcoat layer, and the lower row is the residual rate of color density when the same film is layered on the back side of thermal paper. In practical terms, chemical-resistant thermal paper is often used sandwiched between vinyl chloride films, and those with higher values in both the upper and lower rows of Table 1 are practical. . In terms of overcoating agents, the one of the present invention is good, while the water-insoluble compound styrene-butadiene rubber shown in Comparative Example 6 has poor chemical resistance, and as seen in Comparative Examples 1, 3, and 4, it has poor chemical resistance. It has been found that treating the underlying support with styrene-butadiene rubber does not prevent plasticizer penetration from the back side of the paper. The best way to pre-treat the support is to apply it directly below the heat-sensitive layer, that is, undercoat it.
Next, it is better to process the back side of the support. The size press method for the support has the advantage that it can be done on-machine together with the papermaking of the base paper, but on the other hand, if a large amount is processed to the extent that a film is formed, the problem of statesking to the dryer remains. However, it was found to be highly effective in terms of chemical resistance and to be sufficient and practical as bar coat paper for POS.

Claims (1)

[Claims] 1. A layer mainly composed of a water-soluble polymer compound is provided on the front and/or back side of the support, and a dye precursor and the dye are added on one side of the pretreated support when heated. A chemical-resistant thermal paper comprising a thermosensitive coloring layer whose main component is a color developer that develops color from a precursor, and further provided with an overcoat layer containing alginate on the thermosensitive coloring layer. 2. The chemical-resistant thermal paper according to claim 1, wherein the overcoat layer contains alginate as a main component. 3. The chemical-resistant thermal paper according to claim 1, wherein the overcoat layer is mainly composed of an alginate and a water-soluble polymer compound excluding the alginate. 4. The chemical-resistant thermal paper according to claim 3, wherein the water-soluble polymer compound is at least one of hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol.