JPS63312883A - Thermosensitive recording material - Google Patents

Abstract

PURPOSE:To prevent ground fogging and impart a conductive property, by providing a layer comprising a colorless or light-colored dye precursor, a color developer and an amine salt of styrenesulfonic acid on a base to produce a thermosensitive recording material. CONSTITUTION:A colorless or light-colored dye precursor and a color developer are separately dispersed in solvents, the two dispersed compositions thus obtained are mixed with each other, and an amine salt or quaternary ammonium salt of polystyrenesulfonic acid is mixed to the mixture to prepare a coating liquid. The coating liquid is applied to a base such as a paper, a synthetic paper and a synthetic resin film, followed by drying to produce a thermosensitive recording material. The color developer is used in an amount of ordinarily 1-50pts.wt., preferably, 4-10pts.wt. per 1pts.wt. of the dye precursor. The amine salt of polystyrenesulfonic acid for imparting a conductive property is used so that the surface resistance of the base will be not more than 5X10<11>OMEGA at a temperature of at least 20 deg.C in an atmosphere of 40%RH.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-sensitive recording material. Specifically, the present invention relates to a heat-sensitive recording material comprising a dye precursor, a color developer that causes color development when heated, and a conductive compound.

[Prior Art] Thermosensitive recording paper is generally a recording sheet that develops color through a thermal reaction between a dye precursor such as a leuco dye and a color developer such as a phenol compound. A heat-sensitive recording material containing the above two components can be uniformly dispersed in water, applied to a support, and dried. However, when this thermal recording paper receives a large number of originals, it tends to be charged with static electricity after recording, which often causes problems such as the recording papers sticking to each other or sticking to the machine's collection tray, making it impossible to eject the paper. do.

In order to improve these problems, ammonium polystyrene sulfonate has been proposed as a heat-sensitive recording material.

[Problems to be Solved by the Invention] However, polystyrene ammonium sulfonate has a large background fog.

[Means for Solving the Problems] The present inventors have arrived at the present invention as a result of studying conductive heat-sensitive recording materials that are free from background fog.

The present invention is a heat-sensitive recording material comprising a colorless to light-colored dye precursor, a color developer, and an amine salt or quaternary ammonium salt of polystyrene sulfonic acid.

The present invention will be explained in more detail below.

The amine salt of polystyrene sulfonic acid and its quaternary ammonium salt used in the present invention are water-soluble or dispersible,
It consists of the following (A) amine salt and (B) quaternary ammonium salt.

(A) Amine salt The amine that forms the salt has the general formula % formula % (1) (wherein, R1 is an argyl group having 1 to 7 carbon atoms, an aryl group, or a hydroxyalkyl group having 2 to 4 carbon atoms). , R2
, R3 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a hydroxyalkyl group having 2 to 4 carbon atoms.

Examples of such amines include argylamines such as trimethylamine, triethylamine, tributylamine, diethylamine, dibutylamine, butylamine, aniline,
Examples include arylamines such as benzylaniline, alkanolamines such as triethanolamine, jetanolamine, monoethanolamine, and monoethanoldimethylamine.

(B) Quaternary ammonium salt The quaternary ammonium base forming the quaternary ammonium salt has the general formula % formula % (2) (wherein R4, R5, R6, and R7 have a carbon number of 1 to 7 (alkyl group or aryl group).

As this quaternary ammonium base, hydroxyte I
・Laethylammonium, hydroxytrimethylethylammonium, hydroxytetramethylammonium,
There are hydroxytetraalkyl(aryl)ammoniums such as hydroxytrimethylbenzylammonium.

Polystyrene sulfonic acid includes not only sulfonated polystyrene homopolymers, but also sulfonated styrene copolymers and copolymers of polystyrene nulphonate.

Monomers that copolymerize with styrene include aliphatic monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, stearyl methacrylate, and vinyl acetate, vinylnaphthalene, and vinyl toluene. , p
- Hydrophobic monomers such as aromatic monomers such as methylstyrene, and carboxylic and sulfonic acid groups such as maleic anhydride, itaconic anhydride, acrylic acid, methacrylic acid, vinyl sulfonic acid, and 2-methylpropylacrylamide sulfonic acid. Containing hydrophilic monomers can be mentioned.

The average molecular weight of polystyrene sulfonate is usually 10
000,000 to 1,000,000, preferably 5,000 to 100,000.

The content of sulfonic acid groups in polystyrene sulfonate is
It is necessary to have a colloid equivalent value of 2+++ eq/g or more, and if it is less than this, the conductivity will deteriorate.

As the colorless or light-colored dye precursor, those used in conventional heat-sensitive recording materials can be used.

Examples include, but are not limited to, fluorane-based, triarylmethane-based, diphenylmethane-based,
Phenonithiazine type, spiropyran type, etc. are used.

Examples of fluoran-based compounds include 3-diethylamino-6-methyl-7-anilinofluoran, 8-(N-ethyl-p
-) Luidino)-6-methyl-7-anilinofluorane, 8-diethylamino-6-methyl-7(o-,p-
dimethylanilino)fluoran, 8-pyrrolidino-6-
Methyl-7-anilinofluorane, 3-piperidino-6
-Methyl-7-anilinofluorane, 3-(N-chlorohexyl-N-methylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-7-(m-1-lifluoromethylanilino ) Fluorane, 3-dibutylamino-7-(.

-chloroanilino)fluoran, 3-diethylamino-
Examples include 6-methyl-7-chlorofluoran, 3-ethylamino-6-methyl-fluoran, and 3-cyclohexylamino-6)-7-chlorofluoran.

As the triarylmethane type, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl) )-3-(1,
2-dimethylindol-3-yl)phthalide, 3-(
p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide.

Examples of diphenylmethane types include 4,4-bis-dimethylaminobenzhydrin benzyl ether and N-halophenylleucoauramine; examples of phenothiazine types include benzoylleucomethylene blue p-nitrobenzylleucomethylene blue; examples of spiropyran types include 3-methyl -spiro-dinaphthopyran, 3-ethyl-spiro-
Examples include dinaphthopyran.

These dye precursors may be used alone or in combination of two or more.

As the color developer, various electron-accepting substances can be used that react with the dye precursor when heated to develop color.

It is also required to have a high degree of thermal responsiveness, no background fog, good image preservation and contact stability, and excellent head matching properties. Therefore, it is necessary to have characteristics such as a sharp melting point in an appropriate temperature range, high compatibility with the dye precursor, high stability of the reaction product, and extremely low solubility in water. .

As such electron-accepting substances, phenols, naphthols, aromatic carboxylic acids, inorganic solid acids, etc. can be used, and specific examples thereof include the following.

4.4-isopropylidene diphenol, 4,4-isopropylidene (2-chlorophenol), 4゜4-isopropylidene bis(2-methylphenol), 4,4-
Cyclohexylidene diphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol novolac type phenolic resin, phenol polymer, p-
Benzyl hydroxybenzoate, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate, 4-hydroxydiphenylsulfone, 1-hydroxy-2-naphthoic acid, 2
-Hydroxy-6-naphthoic acid, bis(4-hydroxydiphenyl) sulfide, 3,5-di-tert-butylsalicylic acid, terephthalic acid, 3-5ee-butyl-4
- Acids such as hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3,5-di-α-methylbenzyl salicylic acid, salts of polyvalent metals such as zinc, magnesium, aluminum, calcium, etc. white clay,
There is activated clay.

In the heat-sensitive recording material of the present invention, the proportions of the dye precursor, color developer and polystyrene sulfonate are appropriately selected depending on the type of material used and are not particularly limited.

The developer is usually used in an amount of 1 to 50 parts by weight, preferably 4 to 10 parts by weight, per 1 part by weight of the dye precursor.

Amine salt of polystyrene sulfonic acid that imparts electrical conductivity;
and quaternary ammonium salt, the surface electrical resistance of the support is at least 5X1 at 20°C and 140% RH.
It is used so that the resistance is 0.011 ohm or less. Excessive use will cause the recording paper to become sticky and cause trouble in feeding the ejected paper.
Avoid excessive use that would result in a resistance of 108 ohms or less. Most preferably, a range of 1×10 9 to 1×10′1 ohm is used. The amount used is usually 0.1 to 3 g/m 2 based on the dry weight of the support.

A method for producing heat-sensitive recording paper using the heat-sensitive recording material of the present invention will be explained.

A dye precursor and a color developer are separately dispersed to produce a dispersion composition. Next, the respective dispersion compositions are mixed and the mixture is coated on a support (paper, synthetic paper, film, etc.) to produce recording paper. The polystyrene sulfonate of the present invention can be applied in advance or added internally before coating the surface of the support with the mixture, or it can be applied to the back side of the produced recording paper or added to the mixture. mixed. Generally, before applying the mixture to the surface of the support, it is applied as is or mixed with an aqueous solution of oxidized starch and polyvinyl alcohol and applied using a size press or the like.

Specifically, the dye precursor (or color developer) and binder are ground and dispersed in water together with a surfactant if necessary using a ball mill, atlander, sand grinder, etc., and then coated. In some cases, the dye precursor (or color developer) may be pulverized in advance into a fine powder and then dispersed in water containing a binder and a surfactant to form a coating solution.

The surfactant can be arbitrarily selected from anionic and nonionic surfactants and includes, for example, sodium 2-ethylhexylsulfosuccinate, sodium naphthalenesulfonate formalin condensate, and the like.

Examples of binders include polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, and carboxymethylcellulose, gelatin, casein, gum arabic, polyvinylpyrrolidone, acrylamide (meth)acrylate copolymer, and styrene anhydride. Maleic acid copolymer salt, styrene-butadiene copolymer emulsion, etc. are usually 10 to 40% by weight of the total solids, preferably 15 to 30% by weight.
% by weight is used.

Furthermore, various auxiliary agents can be added to the mixture. For example, inorganic pigments such as kaolin, clay, talc, calcium carbonate, titanium oxide, silica, zinc oxide, aluminum hydroxide, barium sulfate, urea-formalin resin, organic fine powders such as polystyrene, stearic acid, polyethylene, and carnauba wax calcium. , dispersions such as ester wax, ultraviolet absorbers such as benzophenone type and triazole type, antifoaming agents,
There are fluorescent dyes, etc. Furthermore, stearamide, methylene bisamide stearate, oleic acid amide, and valmitic acid amide can be added as a sensitizer if necessary.

The method for forming the mixture of the dye precursor and the color developer on the support is not particularly limited, and can be formed according to conventionally known techniques. For example, it is formed by applying a mixed solution using air knife coating, blade coating, etc. and drying it. Furthermore, the coating speed of the mixed liquid is not particularly limited, but it is usually in the range of 2 to 12 g/m2, preferably 3 to 10 g/m2 in terms of dry weight.

[Example] The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto. Parts and percentages in the examples are by weight.

Example 1 This example uses 3-hydroxy-6- as the dye precursor.
Methyl-7-anirite fluorane, 4,4 as color developer
-Isopropylidenediphenol is a thermal recording material using polystyrene sulfonic acid triethanolamine salt as a conductive compound.

Oxidized starch 1 on high-quality paper with an absolute dry weight of 50 g/m”
, 0%, polystyrene sulfonic acid triethanolamine salt 0.5%, and water 98.5%, the size press solution was applied using the size press method at a rate of approximately 2.0 g/m'' to form a conductive support. I got it.

Next, Solution A: 1 part of 3-hydroxy-6-methyl-7-anilite fluorane, 5% polyvinyl alcohol aqueous solution, and 5 parts of B? ? ff 1 part of 4,4-isopropylidenediphenol and 5 parts of a 5% polyvinyl alcohol aqueous solution were each ground in a ball mill for 2 days to produce a dispersion. The dispersed liquids A, B, and C (20% stearic acid amide dispersion) were mixed into A:B:C=l:5:3.
A heat-sensitive coating solution was prepared by mixing the two to obtain a heat-sensitive coating solution.

After dry coating, this heat-sensitive coating liquid was applied to the conductive support at a coating thickness of approximately 7 g/m2, dried at a temperature not exceeding 60°C, and further smoothed using a super calender. was adjusted so that the time was 250 seconds, and thermal recording paper was prepared.

The test results of this thermal recording paper are shown in Table 1.

Examples 2 to 4 Regarding the soot press liquid of Example 1, triethyl salt, trimethylamine salt, and trimethylammonium salt of polystyrene sulfone were used as conductive compounds instead of polystyrene sulfonic acid doliethanolamine salt, respectively. Thermosensitive recording paper was also created using the same method.

Comparative Examples 1 to 2 Thermosensitive recording paper was prepared in the same manner as in Example 1, except that no conductive compound was used and ammonium polystyrene sulfonate was used as the conductive compound.

Table 1 Method of measuring surface resistance value Using the equipment specified in JIS C2122,
The heat-sensitive recording paper was kept in an environment of 0° C. and 40% RH for 4 hours and then measured.

Measuring method of soil strength Buri The reflection density of the non-recording area was measured using a Macbeth densitometer.

Tray Accommodation Test Method Heat-sensitive recording paper is continuously scanned 2 times using A4 size facsimile test chart No. 4 using a high-speed thermal facsimile machine.
0 sheets were recorded, and the tray storage status of A4 size recording paper that was automatically cut after recording was investigated.

○ indicates that 20 sheets have been stacked smoothly. × indicates that the recording paper is stuck together and cannot be stacked on the tray. A thermal recording material made of an amine salt or a quaternary ammonium salt does not cause background fog, provides excellent conductivity to thermal recording paper, and improves the accommodation capacity of a tray. Furthermore, in the case of sodium polystyrene sulfonate, the thermal head was highly abrasive, whereas thermal recording materials containing amine salts or quaternary ammonium salts of polystyrene sulfonic acid were less abrasive.

Claims (1)

[Claims] 1. A heat-sensitive recording material comprising a colorless or light-colored dye precursor, a color developer, and an amine salt or quaternary ammonium salt of polystyrene sulfonic acid.