JPH0534148B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Industrial Application Field The present invention relates to a heat-sensitive recording sheet whose main components are a dye precursor and a color developer that develops color when the dye precursor is heated, and an overcoat layer with excellent film properties is provided. Accordingly, the present invention relates to a heat-sensitive recording sheet that prevents deterioration of blank areas and colored areas due to chemicals and improves ink receptivity. (B) Prior art and its problems Heat-sensitive 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, which becomes opaque when heated; A method in which the layer becomes transparent and an image is formed by the colored layer underneath. (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. Excellent products that meet many of these requirements can be manufactured, but in practical handling after recording, if they come into contact with erasers or vinyl chloride bags containing a large amount of plasticizer,
If the image is touched with hands covered with hand cream or hair styling oil, if it is overlapped with diazo-sensitive paper that has just been processed, or if an underline or other writing is made with a fluorescent pen, the image may disappear or the background may become distorted. This has the disadvantage that color fog occurs, making it difficult to read the recorded image. In this decoloring development, the lactone ring of the color-forming lactone compound ring-opened with an acidic developer can be used as a plasticizer such as dibutyl phthalate, dioctyl phthalate, or dioctyl adipate, or as a humectant in a fluorescent pen such as ethylene glycol. This is thought to be due to ring closure in its presence. Also,
The fogging phenomenon is thought to be caused by the developer of the diazo-sensitive paper and the solvent contained in the fluorescent pen dissolving the color developer and bringing it into contact with the dye precursor to cause a color reaction. Therefore, it has been proposed that this phenomenon can be prevented by forming a film on the thermosensitive recording paper to prevent the penetration of plasticizers and the like. (Unexamined Japanese Patent Publication 1973-
(No. 128347, Japanese Unexamined Patent Publication No. 54-3549) The present inventors also developed an overcoat agent with chemical resistance and filed applications in Japanese Patent Application No. 182557-1982 and Japanese Patent Application No. 981-1983. ing. However, regarding the surface properties of the overcoat layer, since it is mainly composed of a water-soluble polymer compound, so-called blocking, in which the front and back surfaces of the heat-sensitive recording paper are likely to partially adhere to each other, tends to occur. Since this phenomenon causes destruction of the overcoat layer, paper breakage, etc. during the processing stage, attempts have been made to prevent this by adding various waterproofing agents and mold release agents. Furthermore, with the aim of increasing the protection efficiency against water and oil, water and oil repellents such as fluororesin are added to the overcoat layer to improve water and oil resistance. However, when using these additives for printing, stamping, writing with a felt-tip pen, etc., the ink may not dry properly or smudge extremely much.
That is, the ink receptivity is poor and, in some cases, the ink becomes unreadable. To improve this drawback, adding a white pigment with high oil absorption can be effective to some extent, but the quantity is limited because it inhibits the formation of a film-like film, reduces color development sensitivity, and causes wear of the facsimile heat head. However, at present, nothing satisfactory has been achieved. (C) Purpose of the Invention The present inventors have conducted intensive studies on a heat-sensitive recording sheet provided with an overcoat layer that has good ink receptivity and does not inhibit color development, reduce sensitivity, or wear out the facsimile heat head, and as a result, has developed the present invention. reached. (D) Structure of the Invention That is, the present invention provides the heat-sensitive recording sheet of the method (3) above, in which N-
The object of the present invention is to provide a heat-sensitive recording sheet "same as claimed", which is characterized by containing an acylamino acid ester, an N-acylamino acid amide, or an N-acylamino acid amine salt. The main components used in the present invention will be explained in detail below, but the present invention is not limited thereto unless it exceeds the gist of the present invention. Table 1 shows typical examples of dye precursors that develop color with phenolic substances or organic acids.

[Table] Rofluorane Next, representative examples of the phenolic substance or organic acid (color developer) used in the present invention are shown in Table-2.

[Table] The thermal recording paper of the present invention can be obtained by the following method. That is, a phenolic substance or an organic acid, and a dye precursor that develops color with the phenolic substance or organic acid are ground and dispersed separately or simultaneously in a grinder into fine particles, mixed with a binder, pigment, etc. The coating liquid is prepared by adding additives. Examples of the binder include water-soluble binders such as starch, hydroxyethylcellulose, methylcellulose, polyvinyl alcohol, styrene-maleic anhydride copolymer, styrene-butadiene copolymer, polyacrylamide, carboxymethylcellulose, gum arabic, and casein. Latexes such as styrene-butadiene latex can be used. Examples of pigments include diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, and the like. In addition, higher fatty acid metal salts such as zinc stearate and calcium stearate, waxes such as paraffin, oxidized paraffin, polyethylene, oxidized polyethylene, stearic acid amide, and castor wax, and wetting agents such as dioctyl sodium sulfosuccinate, Ultraviolet absorbers such as benzophenone type and benzotriazole type, as well as surfactants, fluorescent dyes, etc. can be used. Paper is mainly used as the support for the heat-sensitive recording material according to the present invention, but various non-woven fabrics,
Plastic film, synthetic paper, metal foil, etc., or a composite sheet of a combination of these may be used as desired. Next, regarding the material forming the overcoat layer in the present invention, water-soluble polymer compounds are generally preferred, and acrylic materials such as alginate, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, and polyvinyl alcohol and acrylamide are preferred. Graft copolymers with monomers may be used alone or in combination of two or more. In addition, film-forming polymer emulsions such as acrylic latexes, vinyl acrylic resins, vinyl acetate/ethylene copolymers, silicone/acrylate resins, and styrene/butadiene latexes have been introduced with great success. However, it is necessary that the main component is a water-soluble polymer compound. Furthermore, it is preferable to use one or more of a water resistance agent, an ultraviolet absorber, and a mold release agent in combination to impart water resistance and light resistance, and to prevent film peeling (blocking) due to adhesion. As the N-acylamino acid ester, N-acylamino acid amide or N-acylamino acid amine salt which is a feature of the present invention, so-called amino acid gelling agents disclosed in Japanese Patent Publication No. 13434/1988 can be used. More specifically,

[Table] Examples include amides, but various combinations of raw material N-acylamino acids and alcohols or amines are possible. Moreover, not only single addition but also combined addition is effective. In the present invention, the amount of N-acylamino acid ester, N-acylamino acid amide, or N-acylamino acid amine salt added to the overcoat layer is 0.5% by weight or more, preferably 1 to 60% by weight.
is good in terms of ink receptivity improvement effect, color development sensitivity, and printability. This is because the amount added is 0.5% by weight.
If the amount is less, the effect of improving ink receptivity tends to be insufficient. If it exceeds 60% by weight, the effect of improving ink receptivity is sufficient, but it tends to have an adverse effect on coloring sensitivity and printability because it inhibits heat conduction to the coloring layer. (E) Examples The present invention will be explained in more detail with 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 Benzyl p-hydroxybenzoate... ...40 g Dibenzyl terephthalate ...10 g 10% by weight polyvinyl alcohol aqueous solution ...75 g Water Solutions A and B were ground and dispersed in separate ball mills for 48 hours to prepare a coating solution with the following formulation. Calcium carbonate...20g Solution B...60g 10% by weight aqueous polyvinyl alcohol solution...70g Solution A...20g Water...60g The prepared coating solution was applied to a base paper with a basis weight of 49g/ ^m2 , after drying, the amount of coating was 5g/ Coat the film to a thickness of m ² and heat it at 60°C.
After drying for a minute, heat-sensitive recording paper was prepared by using a super calendar to achieve a Beck smoothness of 100 seconds or more. Liquid C 7% by weight ammonium alginate aqueous solution (manufactured by Fuji Chemical Industry Co., Ltd., product name: Snow Ammon)
...72g 15% by weight polyvinyl alcohol/acrylamide copolymer aqueous solution (manufactured by Showa Denko K.K., trade name: Papilol) ...40g 30% by weight zinc stearate dispersion ...10g Liquid D N-Lauroylglutamic acid dibutylamide
...35g 10% by weight aqueous polyvinyl alcohol solution...17.5g Water...47.5g Solution D was pulverized and dispersed in a ball mill for 48 hours. An overcoat coating solution prepared by adding 3g of Solution D to Solution C has a dry film thickness of approximately 6μm.
The mixture was coated on the above-mentioned thermal recording paper to give an overcoat thermal recording paper of approximately 800 seconds using a super calendar. Example 2 An overcoated thermosensitive recording paper was obtained in the same manner as in Example 1 except that N-palmitoyl-ε-aminocaproic acid lauryl ester was used in place of the N-lauroylglutamic acid dibutylamide used in Example 1. Example 3 An overcoated thermosensitive recording paper was obtained in the same manner as in Example 1 except that N-lauroyl valine laurylamine salt was used in place of the N-lauroylglutamate dibutylamide used in Example 1. Comparative Example Same procedure as in Example except that only liquid C was used.
An overcoated thermosensitive recording paper was produced. Test example Diazo developer resistance test: The overcoated thermal recording paper obtained in Examples 1 to 3 and the comparative example was
After developing the color with UF-920 to an optical density of 1.20, the overcoat treated surface is overlaid with the developed diazo photosensitive paper (developer activator PD) surface.
After being left at room temperature for 3 minutes, the presence or absence of fogging on the background area and deterioration of the colored area was observed. Through the above test, it is possible to determine whether or not the overcoat layer has chemical resistance, that is, the degree of film completion. In particular, when observing blank areas, areas that are not protected by the film develop a black color with the diazo developer.
The presence of cissing, pinholes, and unevenness can be identified. Ink bleed test: On the blank part of the overcoated thermal recording paper of Examples 1 to 3 and the comparative example, stampers manufactured by Shachihata Kogyo Co., Ltd., trade name: Shachihata After stamping with a pilot stamp pad and leaving it at room temperature for 24 hours, ink bleeding was observed. As a result, in the comparative example, there was no deterioration in the reading of the colored part due to fogging of the background caused by the diazo photosensitive paper developer, but the ink bleeding of the stamp was so severe that it became almost impossible to read. On the other hand, the product of the present invention not only has no deterioration in legibility caused by the developer for diazo photosensitive paper, but also has no ink smudges from stamps, etc., and there is no observable smearing of letters in small areas, which is extremely satisfactory. Ink receptivity could be obtained. (F) Effects of the invention A highly reliable heat-sensitive recording sheet using a dye precursor without image deterioration or ink bleeding was obtained. Facsimile paper, POS labels, tickets,
It has been recognized to have extremely high utility value in measurement record charts, etc., and there is a possibility that it will be used in many more fields in the future.

Claims (1)

[Claims] 1. A heat-sensitive coloring layer is provided whose main components are a colorless or light-colored dye precursor and a color developer that reacts with the dye precursor when heated, and furthermore, a water-soluble polymer is provided on this heat-sensitive coloring layer. In a heat-sensitive recording sheet provided with an overcoat layer mainly containing a compound, the overcoat layer contains an N-acylamino acid ester, an N-acylamino acid amide, or an N-acylamino acid amide.
- A heat-sensitive recording sheet characterized by containing an acylamino acid amine salt.