JPH0259787B2 - - 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. The present invention provides a heat-sensitive recording paper that is less susceptible to deterioration due to chemicals.

Thermosensitive recording paper consists of (1) a substrate coated with carbon or colored dyes and pigments, and an opaque thermofusible substance coated on top; 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, but also that the background is white, the colored image is stable for a long time and cannot be worn, there is no residue during recording, and there is no possibility that it will stick to the thermal head during recording ( States King) There are things that you should not do. 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 you touch it with hands covered with hand cream or hair styling oil, if you overlap it with diazo photosensitive paper that has just been processed, or if you write underlines etc. with a highlighter, the image will disappear or the background will become discolored. This has the disadvantage that fog occurs, making it difficult to read the recorded image. This discoloration phenomenon is thought to be because the lactone ring of the color-forming lactone compound, which has been ring-opened with an acidic developer, is closed in the presence of a plasticizer such as dibutyl phthalate, dioctyl phthalate, or dioctyl adibate. ing. It is also believed that the fogging phenomenon is caused by the developer of the diazo photosensitive 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 coloring reaction.

Therefore, it has been proposed that such development can be prevented by forming a film on the heat-sensitive recording paper to prevent penetration of the plasticizer. (Japanese Patent Publication No. 54-128347,
(Japanese Patent Application Laid-Open No. 543549) The present inventors have also developed an overcoat agent having chemical resistance and have filed applications in Japanese Patent Application No. 182557-1982 and Japanese Patent Application No. 981-1981.

However, regarding the surface characteristics 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, these additives cause the inconvenience that when printing, stamping, writing with a felt-tip pen, etc., the ink bleeds extremely, and in some cases becomes unreadable. To improve this drawback, adding a white pigment with high oil absorption can be effective to some extent, but the amount 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, the current situation is unsatisfactory.

The present inventors have developed a thermal recording medium that has chemical resistance and no ink smearing, is free from scum, staining, inhibits color development, or decreases in sensitivity, and has good print quality. As a result of intensive research regarding paper, we have arrived at the present invention.

That is, the present invention provides an overcoat layer mainly composed of a water-soluble polymer compound provided on the thermal recording paper of the method (3) above, in which a condensation product of an aromatic aldehyde and a polyhydric alcohol having a valence of 5 or more is added. It is an object of the present invention to provide a chemical-resistant thermal paper with improved ink bleeding, which is characterized by containing a substance therein.

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 1 (1) Crystal violet lactone (2) 3-indolino-3-p-dimethylaminophenyl-6-dimethylaminophthalide (3) 3-diethylamino-7-chlorofluorane (4) 3-diethylamino -7-cyclohexylaminofluorane (5) 3-diethylamino-5-methyl-7-t-
Butylfluorane (6) 3-diethylamino-6-methyl-7-anilinofluorane (7) 3-diethylamino-6-methyl-7-p-
Butylanilinofluorane (8) 2-(N-phenyl-N-ethyl)aminofluorane (9) 3-diethylamino-7-dibenzylaminofluorane (10) 3-cyclohexylamino-6-chlorofluorane ( 11) 3-diethylamino-6-methyl-7-xylidinofluorane (12) 2-anilino-3-methyl-6-(N-ethyl-p-toluidino)fluoran (13) 3-pyrrolidino-6-methyl- 7-anilinofluorane (14) 3-pyrrolidino-7-cyclohexylaminofluorane (15) 3-pyrrolidino-6-methyl-7-toluidinofluorane (16) 3-pyrrolidino-6-methyl-7- Anilinofluorane (17) 3-(N-methylcyclohexylamino)-
6-Methyl-7-anilinofluorane (18) 3-diethylamino-7-(m-trifluoromethylanilino)fluorane (19) 3-diethylamino-6-methyl-7-chlorofluorane Next, the present invention Table 2 shows typical examples of phenolic substances or organic acids (color developers) used in

Table 2 (1) 4,4'-isopropylidene diphenol (2) 4,4'-isopropylidene bis(2-chlorophenol) (3) 4,4'-isopropylidene bis(2-tert-butylphenol) ) (4) 4,4'-Secondary-butylidene diphenol (5) 4,4'-(1-methyl-n-hexylidene) diphenol (6) 4-phenylphenol (7) 4-hydroxydiphenoxide ( 8) Methyl-4-hydroxybenzoate (9) Phenyl-4-hydroxybenzoate (10) 4-hydroxyacetophenone (11) Salicylic acid anilide (12) 4,4'-Cyclohexylidene diphenol (13) 4,4' -Cyclohexylidenebis(2-methylphenol) (14) 4,4'-benzylidenediphenol(15) 4,4'-thiobis(6-tert-butyl-3-methylphenol) (16) 4,4' -isopropylidene bis(2-methylphenol) (17) 4,4'-ethylenebis(2-methylphenol) (18) 4,4'-cyclohexylidene bis(2-isopropylphenol) (19) 2,2 '-dihydroxydiphenyl(20) 2,2'-methylenebis(4-chlorophenol) (21) 2,2'-methylenebis(4-methyl-6-
(t-butylphenol) (22) 1,1'-bis(4-hydroxyphenol)
-Cyclohexane(23) 2,2'-bis(4'-hydroxyphenyl)
Propane (24) Novolak phenolic resin (25) Halogenated novolak phenolic resin (26) α-naphthol (27) β-naphthol (28) 3.5-di-t-butylsalicylic acid (29) 3.5-di-α-methyl Benzylsalicylic acid (30) 3-methyl-5-t-butylsalicylic acid (31) Phthalic acid monoanilinoparaethoxybenzoic acid (32) Parabenzyloxybenzoic acid (33) Parahydroxybenzoic acid benzyl ester 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 aluminum hydroxide,
Heavy and light calcium carbonate, zinc oxide, titanium oxide, barium sulfate, silica gel, activated clay, talc, clay, satin white, kaolil night, calcined kaolinite, diatomaceous earth, synthetic kaolinite, polyolefin grains, polystyrene grains, urea. Examples include formalin resin particles.

Next, regarding the material forming the overcoat layer in the present invention, water-soluble polymer compounds are generally preferred, among which alginate alone or alginate is essential, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, It is preferable to use one or more polymer compounds selected from polyvinyl alcohol in combination. (Japanese Patent Application No. 152455/1982) The condensation products of aromatic aldehydes and polyhydric alcohols having a valence of 5 or more, which are the characteristics of the present invention, include:
For example, so-called gelling agents described in Japanese Patent Publication No. 51-48465, Japanese Patent Application Laid-open No. 54-33533, etc. can be used.

Examples of polyhydric alcohols having a valence of 5 or more include arabitol, xylitol, sorbitol, mannitol, and the like. Examples of aromatic aldehydes include benzaldehyde and nuclear-substituted benzaldehyde. Examples of substituents that can be used include one or a combination of two or more of alkyl groups, alkoxyl groups, hydroxyl groups, and halogens.

In addition, in the present invention, the amount of the condensation product of aromatic aldehydes and polyhydric alcohol of 5 or more valences added to the overcoat layer is 0.5% by weight or more, preferably 1 to 60% by weight, to prevent ink bleeding. Good in terms of prevention effect, color development sensitivity, and printability. because,
If the amount added is less than 0.5% by weight, the effect of preventing ink bleeding tends to be insufficient. Also,
If it exceeds 60% by weight, the effect of preventing ink bleed is sufficient, but it inhibits heat conduction to the coloring layer.
It tends to have a negative effect on color development sensitivity and printability.

Furthermore, water resistance can be achieved by using one or more of water resistant agents, water repellents, detergent detergents, and ultraviolet absorbers in combination.
It is preferable to use one that imparts light resistance and prevents the formation of pinholes.

In addition, in the present invention, the thickness of the dry film of the overcoat layer is 0.5 μm or more, preferably 3 to 3 μm.
A thickness of 12 μm is desirable in terms of chemical resistance and color development sensitivity.
If the thickness of the coating is less than 0.5 μm, the chemical resistance will not be sufficient, and if it exceeds 12 μm, the color development sensitivity will tend to decrease.

The support to which the heat-sensitive coating liquid is applied is generally paper, but any material such as synthetic paper or synthetic resin film can also be used.

Example 1 Solution A 3-(N-methylcyclohexylamino)-6-
Methyl-7-anilinofluorane...12g 10% by weight polyvinyl alcohol aqueous solution...18g Water...30g Liquid 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/ Coat the film to a thickness of m ² and heat it at 60°C.
A thermosensitive recording paper was prepared by drying for a minute.

C Liquid dibenzylidene sorbitol (product name: Gelol D, manufactured by Shin Nippon Chemical Co., Ltd.) ...35g 10% by weight polyvinyl alcohol aqueous solution
...17.5g Water 47.5g Solution C was ground in a ball mill for 48 hours.

D Solution 7% ammonium alginate aqueous solution (manufactured by Fuji Chemical Industry Co., Ltd., product name: Snow Ammon)
...143g Liquid C ...5g Fluororesin (manufactured by Daikin Industries, Ltd., product name: Lupron L-2) ...1g The prepared coating liquid D was coated on the above heat-sensitive record so that the dry film thickness was approximately 5 μm. Overcoat the paper and use a super calendar to obtain a Beck smoothness of about 400 seconds to produce an overcoated thermal recording paper.

Example E Liquid tribenzylidene sorbitol (Shin Nippon Chemical Co., Ltd.)
(manufactured by Gelol T)...35g 10% by weight polyvinyl alcohol aqueous solution
...17.5g Water ...47.5g Solution E was ground in a ball mill for 48 hours.

Using liquid E in place of liquid C in Example 1, the above heat-sensitive recording paper was overcoated to a dry film thickness of about 5 μm, and the Bekk smoothness was about 400 seconds using a super calender. Let it be,
An overcoated thermosensitive recording paper was produced.

Comparative Example 1 F Liquid urea-formalin resin (manufactured by Ciba Geigy,
Product name. : Burgo Pack M2) ...15g 10% by weight polyvinyl alcohol aqueous solution
...7.5g Water ...77.5g Solution F was ground in a ball mill for 48 hours.

In the D solution of Example 1, F solution was used instead of C solution.
Using 14.6 g, the above-mentioned thermosensitive recording paper was overcoated to a dry film thickness of about 5 μm, and the overcoated thermosensitive recording paper was prepared using a super calender to give a Beck smoothness of about 400 seconds.

Comparative Example 2 Using a solution obtained by removing Solution C from Solution D in Example 1, the above heat-sensitive recording paper was overcoated to a dry film thickness of about 5 μm, and the surface smoothness was adjusted to about 400 using a super calender. An overcoated thermosensitive recording paper was prepared.

Example 3 Diazo developer resistance test: The overcoated thermal recording paper obtained in Examples 1 and 2 and Comparative Examples 1 and 2 was colored to an optical density of 1.20 using Panafux UF-920 manufactured by Matsushita Electric Transmission Co., Ltd. rear,
Apply diazo photosensitive paper (developer) to the overcoat treated surface.
RICOPY SD) was placed on the paper immediately after the development process, and then left at room temperature for 3 minutes to observe the presence or absence of fogging development in the background area and deterioration in legibility of the colored area. The above test allows the degree of film completion of the overcoat layer to be ascertained.

Ink bleed test: Shachihata Kogyo Co., Ltd. was applied to the blank area of the overcoated thermal recording paper of Examples 1 and 2 and Comparative Examples 1 and 2.
Product name: Shachihata

As a result, in the comparative example, there was no deterioration in the legibility of the colored part due to the fogging phenomenon of the background part caused by the developer for diazo photosensitive paper, but the ink bleeding of stamps etc. was so severe that it became almost impossible to read. Shimatsuta.

On the other hand, the product of the present invention is extremely satisfactory, not only is there no deterioration in legibility caused by the developer for diazo photosensitive paper, but there is also no ink bleeding from stamps, etc., and there is no observable smearing of even small letters. It was hot.

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. A chemical-resistant thermal recording paper provided with an overcoat layer mainly composed of a compound, characterized in that the overcoat layer contains a condensation product of an aromatic aldehyde and a polyhydric alcohol having a valence of 5 or more. Chemical-resistant thermal recording paper with improved ink bleeding.