JPH074967B2 - Thermal recording material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to improvement in reliability of a recorded image of a thermal recording material using a leuco dye as a color former.

[Prior art]

The heat-sensitive recording material is generally a paper, synthetic paper, plastic film, or other support provided with a heat-sensitive color-forming layer containing a thermo-color-forming composition as a main component, and should be heated with a thermal head, a thermal pen, laser light, or the like. Thus, a color image is obtained. Compared to other recording materials, this type of recording material can perform recording in a short time with a relatively simple device without performing complicated processing such as development and fixing, and has less noise and environmental pollution. ,
Due to its low cost, it is used not only for copying books and documents, but also as a recording material in various fields such as electronic computers, facsimiles, ticket vending machines, labels and recorders. The thermochromic composition used for such a heat-sensitive recording material is generally composed of a color former and a developer that allows the color former to develop color when heated.
For example, a colorless or light-colored leuco dye having a lactone, a lactam or a spiropyran ring, and various types of acidic substances such as organic acids and phenolic substances are used as a color developer. The recording material in which the color-developing agent and the color-developing agent are combined has the advantages that the color tone of the obtained image is particularly clear, the background whiteness is high, and the weather resistance of the image (dye image) is excellent. And is widely used.

In recent years, as the demand for thermal recording materials in place of other conventional recording systems has increased, the demand for quality improvement of thermal recording materials used in this thermal recording system has also increased. Reliability is improved.

The leuco dye normally repeats reversible color development and decolorization, and as long as the leuco dye is used, the problem of image decolorization is posed. For example, if it touches fingerprints or fats and oils, it will disappear, and if it comes in contact with vinyl chloride wrap or adhesive tape,
There is a problem that the plasticizer contained therein causes the color to be erased, and these problems can be said to be major points inferior to other heat-sensitive printing processes, for example, chelate coloring type and thermal transfer recording.

Several proposals have been made in the past to improve the reliability of images. For example, a method using a metal salt of salicylic acid, which is different from an ordinary phenolic compound, as a color developer can be cited, but these color developers remarkably improve the problem of decolorization in the image area, but conversely the background. The inconvenience arises that the parts are colored by oils and fats and plasticizers. A method using orthosulfophthalimide as a color developer has also been proposed, but in this case, the stability of the image area is improved, but the stability of the compound is poor, resulting in a markedly poor storage stability. There is. As another method for improving the image stability, for example, 2,2'-methylenebis- (3-methyl-6-tertiarybutylphenol), 2-oxy-3-naphthoene may be used together with an ordinary phenolic developer. There is a method of adding an image stabilizing aid such as an acid amide, a polybromo compound such as bisphenol A or bisphenol S, etc., but none of them has achieved sufficient image reliability at present.

〔Purpose〕

An object of the present invention is to provide a leuco dye type heat-sensitive recording material having excellent image reliability.

〔Constitution〕

According to the present invention, there is provided a heat-sensitive recording material characterized by containing a compound represented by the following general formula (I) or (II) in a heat-sensitive color forming layer containing a leuco dye and a color developer.

(In the formula, each of R ₁ , R ₂ , R ₃ , and R ₄ is the same or different and represents a hydrogen atom or an alkyl group.) (In the formula, each of R ₁ , R ₂ , R ₃ and R ₄ is the same or different and represents a hydrogen atom or an alkyl group.) The compound of the general formula [I] or the general formula [II] used in the present invention Is usually a white powder, is sparingly soluble in water, and can be used as a developer, but it can also be used in combination with another conventional developer. The amount used can be appropriately selected as necessary, but 0.1 g / m ^{2 to} 5 g / m ² is suitable.

The following are specific examples of the compound of the general formula [I] or the general formula [II].

Di- (4-tert-butylphenyl) phosphonate, di- (4-octylphenyl) phosphonate, di- (2,4-di-tert-butylphenyl) phosphonate, 2,2'-methylenebis- (4-di- Tert-butylphenyl) phosphonate, 2,2'-methylenebis- (3-methyl-6-tert-butylphenyl) phosphonate and the like.

In the present invention, it is essential that these compounds are contained in a thermosensitive coloring layer containing a leuco dye and a color developer, but if necessary, other layers such as an undercoat layer and an overcoat layer may be contained. Good.

The leuco dyes used in the present invention may be used alone or as a mixture of two or more, and as such leuco dyes,
What has been applied to this type of heat-sensitive material is arbitrarily applied, for example, triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, indolinophthalide-based dye leuco compounds are preferably used . Specific examples of such leuco dyes include those shown below.

3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p- Dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chloro Fluoran, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3- Diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-ethylamino) -6-methyl- -Anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6 -Bis (diethylamino) -9- (o-chloroanilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) Fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3- (N-ethyl-N-amylamino) -6-methyl-
7-anilinofluorane, 3- (N-methyl-N-cyclohexylamino) -6-
Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (diethylamino) -5-methyl-7- (N, N-dibenzylamino) fluorane, benzoylleuco methylene blue , 6'-chloro-8'-methoxy-benzoindolino-pyrrilospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrrolispirane, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3 -(2'-methoxy-5'-chlorophenyl)
Phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-nitrophenyl)
Phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl)
Phthalide, 3- (2'-methoxy-dimethylaminophenyl) -3
-(2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilino Fluorane, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5 -Chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) ) Fluoran, 3-diethylamino-5-methyl-7- (α-phenylethylamino) phenyl Oran, 3-diethylamino-7-piperidinocarbonyl fluoran, 2-chloro-3-(N-Mechirutoruijino) -7- (p
-N-butylanilino) fluorane, 3- (N-benzyl-N-cyclohexylamino)-
5,6-benzo-7-α-naphthylamino-4′-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluorane and the like.

In the present invention, various electron-accepting substances are applied as the color developing agent that reacts with the leuco dye when heated to develop it, and a phenolic substance, an organic or inorganic acidic substance or a metal salt thereof, Aromatic amide compound,
Examples thereof include aromatic urea compounds, and specific examples thereof will be shown below.

Clay, activated clay, activated silica, boric acid, zinc oxide, zinc chloride, aluminum chloride, 4,4'-isopropylidene bisphenol, 4,4'-isopropylidene bis- (o
-Cresol), 4,4'-isopropylidene bis (o-t
ert-butylphenol), 4,4'-isopropylidene-
Bis (o-chlorophenol), 4,4'-cyclohexylidene bisphenol, 4,4'-bisphenol sulfone, 4-hydroxy-4'-chloro-diphenyl sulfone, 4-hydroxy-4'-isopropoxydiphenyl sulfone, Isopropyl p-hydroxybenzoate, p-
Benzyl hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate, anilide salicylate, salicylic acid- (o-chloroanilide), salicylic acid- (n-trifluoromethylanilide), dimethyl 4-hydroxyphthalate, 2-hydroxy-3. -Naphthoic acid, benzyl 2-hydroxy-3-naphthoate, 2-hydroxy-3-naphthoic acid anilide, 2-hydroxy-3-naphthoic acid zinc salt, zinc chloride / antipyrine complex, methylenebis- (oxyethylenethio) diphenol , 4-hydroxyacetophenone, novolac type phenol resin, novolac type phenylphenol resin, diphenylthiourea, di (m-chlorophenyl) thiourea, di (m-trifluoromethylphenyl) thiourea type and the like.

In the present invention, in order to bond and support the leuco dye and the color developer on a support, various conventional binders can be appropriately used, and examples thereof include polyvinyl alcohol, starch and its derivatives, methoxycellulose and hydroxy. Cellulose derivatives such as ethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / Maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein and other water-soluble polymers, polyvinyl acetate,
Polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutylmethacrylate, ethylene / vinyl acetate copolymer, styrene / butadiene / acrylic copolymer, etc. Latex can be used.

As the filler used in the present invention, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, inorganic fine powder of surface-treated calcium or silica, etc. Other
Examples include organic fine powders of urea-forimarin resin, starch, styrene / methacrylic acid copolymer, polystyrene resin and the like.

To prepare the heat-sensitive recording material of the present invention, a compound of the above general formula [I] or general formula [II] is prepared on a support such as paper or synthetic paper.
A coating liquid containing a leuco dye, a developer and a binder as main components may be applied and dried.

〔effect〕

The heat-sensitive recording material of the present invention is one in which the reliability of the recorded image is remarkably improved by using the compound represented by the general formula [I] or the general formula [II]. In the case of a thermal recording material using a colorant, even if the image disappears with fingerprints or mending tape, the image of the present invention does not change even after one month, and its effect is It can be said that it is remarkably larger than the conventionally proposed thermal recording materials.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples. All parts and% shown below are based on weight.

Examples 1 to 3 [Solution A] 3- (N-methyl-N-cyclohexylamino) 6-methyl-7-anilinofluorane 10 parts Hydroxyethyl cellulose 10% aqueous solution 10〃water 30〃 [Solution B] Table-1 Color developer 30 parts Hydroxyethyl cellulose 10% aqueous solution 30〃 Water 90〃 [C liquid] 2,2'-methylenebis- (4,6-di-tert-butylphenyl) phosphonate 10 parts Hydroxyethyl cellulose 10% aqueous solution 10 〃 Water 30〃 [D liquid] Silica 20 parts Stearic acid amide 20〃 Polyvinyl alcohol 10% aqueous solution 20〃 Water 140〃 Disperse each of the above [A liquid] to [D liquid] with a ball mill,
The mixture was mixed at an equal ratio to obtain a heat-sensitive coating liquid.

Next, the coating liquid was applied and dried on a high-quality paper having a basis weight of 50 g / m ^{2 so} that the dry adhesion amount was 0.5 g / m ² in terms of the dye amount, and the thermal recording papers of Examples 1 to 3 were obtained. Obtained.

Example 4 In Example 1, 2,2'-methylenebis-of [solution C] was used.
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that bis- (4-tert-butylphenyl) phosphate was used instead of (4,6-di-tert-butylphenyl) phosphate.

Comparative Example 1 A thermosensitive recording paper was obtained in the same manner as in Example 1 except that the [C liquid] was omitted.

Comparative Example 2 In Example 1, [C liquid] 2,2'-methylenebis-
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 2,2 ', 6,6'-tetrabromobisphenol A was used in place of (4,6-di-tert-butylphenyl) phosphate.

Each of the heat-sensitive recording papers obtained above was color-developed with a prototype facsimile printing device at an applied energy of 0.5 mj / dot. The results are shown in Table-1.

Incidentally, the tape resistance was measured by affixing Sumitomo 3M Mending Tape 810 to the printed sample and measuring the density after 3 weeks.

From the above results, the product of the present invention has remarkably excellent tape resistance of the image, and therefore, the image density does not change even after long-term storage at room temperature, and the fingerprint resistance is remarkably excellent. I know there is.

Claims (1)

[Claims] 1. A heat-sensitive recording material comprising a heat-sensitive color forming layer containing a leuco dye and a color developer containing a compound represented by the following general formula (I) or (II). (In the formula, each of R ₁ , R ₂ , R ₃ , and R ₄ is the same or different and represents a hydrogen atom or an alkyl group.) (In the formula, each of R ₁ , R ₂ , R ₃ , and R ₄ is the same or different and represents a hydrogen atom or an alkyl group.)