JPH03213391A - heat sensitive recording material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a heat-sensitive recording material. More specifically,
TECHNICAL FIELD The present invention relates to a heat-sensitive recording material that has excellent color development and other recording properties, and does not flake (whiten) during recording storage.

[Prior Art] Various types of heat-sensitive recording materials have been announced so far that utilize a heat-coloring reaction between at least one colorless or light-colored basic dye and phenols, organic acids, etc.
-14039, etc.) have been widely put into practical use. These heat-sensitive recording materials are applied to a wide range of fields such as measurement recorders, computers and information communication terminals, facsimile machines, and automatic ticket vending machines. These recording devices are equipped with a thermal element such as a thermal head or a thermal pen, and by heating this element, color can be generated and a recording can be obtained. Recently, applications have become more diversified and equipment has become more sophisticated, and along with this, the quality required for heat-sensitive recording materials has also become more sophisticated. For example, for fax, A4
What used to take several minutes to record a size can now be done in less than a minute.

Under these circumstances, the addition of sensitizers has been proposed as a method to improve the sensitivity of thermal recording paper, but there are problems with color development sensitivity, stability of color images, recording suitability, etc. A product that satisfies the various performance requirements in a well-balanced manner has not yet been obtained.

In heat-sensitive recording paper, a color-forming substance and a phenol compound are present in the heat-sensitive recording layer as finely dispersed particles, and it is thought that upon heating, one or both of them will dissolve and come into close contact with each other, producing color. ing.

As a suitable phenol compound to be used for this purpose, 2,2-bis(
4'-Hydroxyphenyl)propane (bisphenol A, melting point 156°C) is widely used (eg US Pat. No. 1,509,375). However, this bisphenol A has poor thermal responsiveness and cannot necessarily satisfy the market demand for higher sensitivity of thermal recording paper as thermal recording apparatuses become faster and more compact. Many sensitizers have been proposed to compensate for this drawback, including waxes (Japanese Patent Application Laid-Open No. 19231-1982) and phthalate esters (Japanese Patent Application Laid-open Nos. 116690-1982 and 58-1982). -98285), benzyl phenyl ether derivatives (JP-A-59-155098), benzylbiphenyl (JP-A-80-82382), naphthol derivatives (JP-A-58-87094), carbonic acid diesters (JP-A-58-87094),
JP-A-58-136489) and the like have been proposed, but when combined with the above-mentioned bisphenol A, sufficient quality has not been obtained in terms of white color, color development sensitivity, fog, etc. Furthermore, in JP-A-56-144193, benzyl p-hydroxybenzoate or methylbenzyl p-hydroxybenzoate is proposed as a color developer for increasing the sensitivity of heat-sensitive recording sheets, but the color develops during recording storage. There is a problem with its shelf life because the whitening (flouring) phenomenon occurs.

As mentioned above, the current situation is that so far they have not been able to fully meet the high quality demands of the market, including color development characteristics and storage stability.

[Problems to be Solved by the Invention] Therefore, there has been a need for a heat-sensitive recording material that is highly sensitive and has excellent storage stability without dusting.

The present invention aims to meet this need.

[Means for Solving the Problems] In order to achieve this objective, the present inventor conducted extensive research and found that di(p-methylbenzyl) oxalate (melting point: 102°C) was used as a sensitizer. We found that it is possible to increase sensitivity by doing this. However, after application and recording, when stored for a long period of time, a powdery (whitening) phenomenon was observed in the recorded area. This is because the sensitizer and developer dissolved by heating recrystallize on the surface, which significantly impairs the quality of the recorded image. Therefore, after researching various means for preventing this dusting phenomenon, the present inventors discovered that methylolated fatty acid amide was effective and completed the present invention.

According to the present invention, the objects of the present invention can be achieved by making di(p-methylbenzyl oxalate) and methylolated fatty acid amide coexist in the heat-sensitive recording layer.

The methylolated fatty acid amide used in the present invention is a compound obtained by adding formaldehyde to a fatty acid amide, and has the general formula RCONHCH20H (R means a linear (may contain a double bond) aliphatic hydrocarbon, and the number of carbon atoms is Usually 12 or more
It is a mono-substituted primary amide that can be represented by (2).

Specific examples include methylolated stearic acid amide CHC0NHCH20H (melting 735 point 109-113°C), methylolated behenic acid amide C
HC0NHCH20H (melting point 107-113°C) 143 and the like, but the present invention is not limited thereto, and various methylolated fatty acid amides may be used in combination.

The methylolated fatty acid amide is added in an amount of 2 to 100 parts by weight, preferably 10 to 50 parts by weight, per 100 parts by weight of di(p-methylbenzyl oxalate). Also, oxalate di(p
-Methylbenzyl) is 10 parts by weight per 100 parts by weight of the color developer.
Add up to 200 parts by weight, preferably 50 to 150 parts by weight.

The use of higher fatty acid amides in heat-sensitive recording layers has been proposed, for example, in Japanese Patent Publication No. Sho 58-2835, but higher fatty acid amides that have not been methylolated cannot suppress the dusting phenomenon mentioned above. Furthermore, the use of methylolated fatty acid amide alone in a heat-sensitive recording layer is described in, for example, JP-A-57188394, but no proposal has been made to use it in combination with di(p-methylbenzyl oxalate). This has never been done, and this results in
It is not known that it is possible to achieve high sensitivity and suppress the dusting phenomenon. This di(p-methylbenzyl) oxalate
Although the specific effect of methylolated fatty acid amide in suppressing dusting has been fully confirmed experimentally, the details of its mechanism are unknown. It is presumed that the polarity of the methylol group has some influence.

As the colorless or light-colored basic leuco dye used to form the heat-sensitive recording layer in the present invention, for example, the following can be used.

For example, basic dyes include triallylmethane dyes such as 3,3-bis(pdimethylaminophenyl)-6-dimethylaminophthalide, 3-diethylamino-6-
Methyl-7-phenylaminofluorane, 3-dibutylamino-6-methyl-7-phenylaminofluorane,
3-(N-cyclohexyl-N-methylamino)-6-
Methyl-7-phenylaminofluorane, 3-dibutylami/-7-(o-chlorophenylamino)fluoran, 3-(N-ethyl-N-isoamyl)amino-6-
Examples include methyl-7-phenylaminofluorane.

Any color developer may be used as long as it has the property of being liquefied or dissolved by an increase in temperature, and also has the property of causing coloration upon contact with the above-mentioned basic dye.

Typical specific examples include 4-tert-butylphenol, 4-acetylphenol, 4-tert-octylphenol, 4,4'-5ee-butylidenediphenol, 4-phenylphenol, 4,4'-dihydroxy-diphenylmethane, 4 .4'-isopropylidene diphenol, hydroquinone, 4,4'-cyclohexylidene diphenol, 4,4'-dihydroxydiphenyl sulfide, 4,4'-thiobis(6-tert
-butyl-3-methylphenol), 4,4'-dihydroxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxybenzophenone, dimethyl 4-hydroxyphthalate, 4-hydroxymethylbenzoate, 4- Ethyl hydroxybenzoate, propyl 4-hydroxybenzoate, 5ec-butyl 4-hydroxybenzoate, phenyl 4-hydroxybenzoate, benzyl 4-hydroxybenzoate, tolyl 4,-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate , phenolic compounds such as 4,4'-dihydroxydiphenyl ether, benzoic acid, p-tart
-Butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, salicylic acid, 3-isopropylsalicylic acid, 3-t
ert-butylsalicylic acid, 3-benzylsalicylic acid,
Aromatic carboxylic acids such as 3-(α-methylbenzyl)salicylic acid and 3,5-di-tert-butylsalicylic acid, and their phenolic compounds, aromatic carboxylic acids and polyvalent metals such as zinc, magnesium, aluminum, and calcium. Examples include organic acidic substances such as salts of

In the heat-sensitive recording material of the present invention, the support material on which the heat-sensitive coloring layer is formed is not particularly limited. For example, paper, pigment coated paper, synthetic fiber paper, synthetic resin film, etc. can be used as appropriate. Paper is generally preferred.

In preparing a coating solution for forming a heat-sensitive coloring layer, water is used as a dispersion medium, and a dye and a coloring agent are dispersed using a grinder such as a ball mill, an attritor, or a sand grinder to form a coating solution. Such a coating liquid contains starches, hydroxyethyl cellulose, methyl cellulose,
Carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene, maleic anhydride copolymer salt, styrene-butadiene copolymer emulsion, etc. are used in an amount of 2 to 40% by weight, preferably 5 to 25% by weight of the total solid content. do. Various auxiliary materials may be added to the coating liquid as necessary. For example, dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, and fatty acid metal salts, as well as antifoaming agents, fluorescent dyes, and coloring dyes can all be added.

A pigment may be used in combination to further whiten the heat-sensitive recording layer or to suppress adhesion of lees to the thermal head. For example, clay, talc, heavy carbonate, light calcium carbonate, silica, calcium silicate, aluminum silicate,
Inorganic pigments such as diatomaceous, aluminum oxide, titanium dioxide, and zinc oxide, organic pigments using urea-formalin, phenol, epoxy, melamine, and guanamine-formalin resin can be used.

Preservability improvers may be added to prevent discoloration after coloring and various waxes may be added to prevent sticking to the thermal head.

Phenolic compounds are effective as storage improvers to prevent color fading after color development, such as 1.1.3-tris(2-methyl-4-hydroxy-5
-t-butylphenyl)butane, 1.1.3-tris(2-methyl-4-hydroxy-
5-cyclohexyl)butane, (1), 1-bis(2-methyl-4-hydroxy5-t-butylphenyl)butane, 4.4'-(1-phenylethylidene)bisphenol, 4.4'-[1 , 4-phenylenebis(1-methylethylidene)] bisphenol, 4.4'-[1,3-phenylenebis(1-methylethylidene)] bisphenol, and the like.

Waxes include higher fatty acids such as stearic acid,
Higher fatty acid metal salts such as zinc stearate, calcium stearate, zinc behenate, and aluminum stearate; higher fatty acid amides such as stearic acid amide, oleic acid amide, erucic acid amide, and behenic acid amide;
Examples include polyethylene wax, paraffin wax, carnauba wax, and microcrystalline wax.

In the heat-sensitive recording material of the present invention, the method of forming the recording layer is not particularly limited. For example, in a method of applying a heat-sensitive coating liquid to a support, an appropriate coating device such as an air knife coater or a blade coater can be used.

The heat-sensitive coloring layer is generally formed to have a dry weight in the range of 2 to 12 g/rd.

Note that various known modifications such as providing an undercoat layer under the heat-sensitive coloring layer may be made as necessary.

[Example] Examples 1 to 2 and Comparative Examples 1 to 2 ■ Preparation of Dispersion A 3-Di-n-butylamino-6 methyl-7-phenylaminofluorane 40 parts by weight Polyvinyl alcohol 10% solution 20 parts by weight Department water
40 parts by weight ■Preparation of dispersion B 4.4'-isopropylidenediphenol 40 parts by weight Polyvinyl alcohol 10% solution 20 parts by weight Water
40 parts by weight Preparation of dispersion C Di-p-methylbenzyl oxalate 40 parts by weight Polyvinyl alcohol 10% solution 20 parts water
40 parts by weight of the above composition for preparing liquids A-C were mixed, and the average particle size was 0.511 using a sand grinder.
It was ground to frI.

(2) Preparation of dispersion liquid 40 parts by weight of light calcium carbonate (Brilliant 15. Shiraishi T-Gyo ■) 0.7% solution of sodium hexametaphosphate 60 parts by weight This composition was dispersed using a colorless method.

Furthermore, as dispersions E, F, G, and H solutions, respectively,
A 20% zinc stearate dispersion, a 20% methylolated behenic acid amide dispersion, a 20% methylolated stearic acid amide dispersion, and a 20% behenic acid amide dispersion were prepared.

Further, a 10% polyvinyl alcohol aqueous solution was used as a binder.

These dispersions and binders were blended so that the weight ratio after drying would be as shown in Examples 1 to 2 and Comparative Examples 1 to 2 in Table 1 to prepare coating liquids. 50g/rr of this coating liquid? Coat it on the base paper, dry it, then super calender it, 4
We created different types of thermal paper.

The four types of thermal paper obtained were measured for recording sensitivity and visually observed for the presence or absence of powdering phenomenon. The results are shown in Table 1.

The recording sensitivity in Table 1 was measured using a commercially available heat-sensitive facsimile modified for testing purposes. 1 line recording time 10m5ec,
Printing of 12 g lines was carried out under the conditions of a scanning line density of 8×8 dots/mm, and the applied energy per dot was 0.39 mJ. Macbeth Densitometer RD measures the color density at that time.
-914, which was taken as a value representative of the recording sensitivity of thermal paper.

In addition, place the printed material whose recording sensitivity was measured in the CHI-Ji Clean Holder CH-5O8 (transparent pocket file), and
Determine the presence or absence of dusting phenomenon after a month.

As shown in Table 1, oxalic acid di(p) is present in the heat-sensitive recording layer.
- methylbenzyl) and methylolated fatty acid amide (Examples 1 and 2), a heat-sensitive recording material with high recording sensitivity and no flaking (whitening) was obtained; If not (Comparative Examples 1 and 2),
No such heat-sensitive recording material was obtained in any case.

[Effects of the Invention] The present invention has made it possible to provide a heat-sensitive recording material that has high recording sensitivity and is free from dusting.

Claims (1)

[Claims] In a heat-sensitive recording material that utilizes a color-forming reaction between at least one basic dye and a color developer capable of forming a color when it comes into contact with the basic dye, the heat-sensitive recording layer contains a formula, a mathematical formula, a chemical formula, a table, etc. A heat-sensitive recording material characterized by containing di(p-methylbenzyl oxalate) indicated by ▼ and a methylolated fatty acid amide.