JPH0696349B2 - Thermal recording material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having improved color developability.

(Prior Art) A heat-sensitive recording material using an electron-donating colorless dye precursor and an electron-accepting compound is disclosed in JP-B-45-14039 and JP-B-43-416.
No. 0, etc. The minimum required performance of such a thermal recording material is (1) sufficient color density and color sensitivity, (2) no fog (color development during storage before use), (3) Although the fastness of the colored body after color development is sufficient, etc., at present, no one completely satisfying these requirements has been obtained.

Especially with the recent increase in the speed of thermal recording systems, the above (1)
The research for

As the method, the melting point of the electron-accepting compound itself may be set to 60 to 100 ° C. However, it is difficult to control the melting point of the phenolic compound which is the most widely used electron accepting compound at present, and the phenolic compound itself is expensive and is not practical.

As other methods, JP-B-49-17748 and JP-B-51-39567 may be used in combination with an organic acid and a phenolic compound as an electron accepting substance, or a polyvalent metal salt of a compound having an alcoholic hydroxyl group. It is described to be used. In addition, Japanese Patent Publication No. 51-29945 describes that a copolymer of hydroxyethyl cellulose and maleic anhydride is used.

Further, Japanese Patent Publication No. 51-27599 and Japanese Patent Application Laid-Open No. 19231/1996 describe adding waxes.

Further, JP-A-49-34842, JP-A-49-115554, JP-A-50-149353, JP-A-52-106746, JP-A-53-5636.
JP-A-53-11036, JP-A-53-48751 and JP-A-56-72996, and thioacetanilide, phthalonitrile, acetamide, di-β-naphthyl-p-phenylenediamine, fatty acid amide. , Nitrogen-containing organic compounds such as anilide acetoacetate, diphenylamine, benzamide, carbazole, etc. or heat fusible substances such as 2,3-di-m-tolylbutane, 4,4′-dimethylbiphenyl,
Alternatively, it is described that a carboxylic acid ester such as dimethyl isophthalate, diphenyl phthalate and dimethyl terephthalate is added as a sensitizer.
British Patent Publication No. 2,074,335A describes addition of hindered phenols.

However, the thermal recording materials produced by using these methods are still insufficient in terms of color density and color sensitivity.

(Object of the Invention) Accordingly, an object of the present invention is to provide a heat-sensitive recording material which has a sufficient color density and color sensitivity and which satisfies other conditions to be satisfied.

(Structure of the Invention) An object of the present invention is to provide a coating liquid containing a dispersion liquid in which at least an electron-donating colorless dye precursor is dispersed, and a dispersion liquid in which an electron-accepting compound is dispersed, on a support. In the heat-sensitive recording material formed by coating, the dispersion liquid in which the electron-accepting compound is dispersed simultaneously contains a diether compound represented by the following general formula (I) as a dispersoid, and also has an electron-accepting property in the dispersion liquid. It has been achieved by a heat-sensitive recording material characterized in that the volume average particle diameter of the mixture of the compound and the diether compound is 3 μm or less.

Ar ₁ —O—CnH ₂ n—O—Ar ₂ (I) In the above formula, Ar ₁ and Ar ₂ represent a substituted or unsubstituted aryl group, and n represents a positive integer of 10 or less.

Examples of the electron-donating colorless dye used in the present invention include triarylmethane compounds, diphenylmethane compounds,
A xanthene compound, a thiazine compound, a spiropyran compound, etc. are used. To illustrate some of these,
As a triarylmethane compound, 3,3-bis (p-
Dimethylaminophenyl) -6-dimethylaminophthalide (ie, crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p
-Dimethylaminophenyl) -3- (1,3-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, etc. There are 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and the like as diphenylmethane compounds, and xanthene Rhodamine-
B-anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine B (p-chloroanilino) lactam, 2-dibenzylamino-6-diethylaminofluorane, 2-anilino-6-diethylaminofluorane, 2-anilino-3 -Methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-cyclohexylmethylaminofluorane, 2-o-chloroanilino-6-diethylaminofluorane, 2-m-chloroanilino-6-diethylaminofluorane, 2 -(3,4-dichloroanilino) -6-diethylaminofluorane, 2
-Octylamino-6-diethylaminofluorane, 2
-Dihexylamino-6-diethylaminofluorane,
2-m-trifluoromethylanilino-6-diethylaminofluorane, 2-butylamino-3-chloro-6-diethylaminofluorane, 2-ethoxyethylamino-
3-chloro-6-diethylaminofluorane, 2-p-
Chloroanilino-3-methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-dioctylaminofluorane, 2-anilino-3-chloro-6-diethylaminofluorane, 2-diphenylamino-6-diethylaminofluor Oran, 2-anilino-3-methyl-
6-diphenylaminofluorane, 2-phenyl-6-
Diethylaminofluorane, 2-anilino-3-methyl-6-N-ethyl-N-isoamylaminofluorane,
2-anilino-3-methyl-5-chloro-6-diethylaminofluorane, 2-anilino-3-methyl-6-diethylamino-7-methylfluorane, 2-anilino-
3-methoxy-6-dibutylaminofluorane, 2-o
-Chloroanilino-6-dibutylaminofluorane, 2
-P-chloroanilino-3-ethoxy-6-N-ethyl-N-isoamylaminofluorane, 2-o-chloroanilino-6-p-butylanilinofluorane, 2-anilino-3-pentadecyl-6-diethylaminofluor Oran, 2-anilino-3-ethyl-6-dibutylaminofluorane, 2-anilino-3-ethyl-6-N-ethyl-N-isoamylaminofluorane, 2-anilino-3
-Methyl-6-N-ethyl-N-γ-methoxypropylaminofluorane, 2-anilino-3-chloro-6-N
-Ethyl-N-isoamylaminofluorane and the like, thiazine-based compounds include benzoylleucomethylene blue, p-nitrobenzyl leucomethylene blue and the like, and spiro-based compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl- Spiro-dinaphthopyran,
3,3'-dichloro-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methyl-naphtho-
(3-Methoxybenzo) spiropyran, 3-propyl-
Examples include spiro-dibenzopyran. These may be used alone or as a mixture.

Examples of electron-accepting compounds are phenol compounds,
Organic acid or its metal salt, oxybenzoic acid ester,
In particular, a phenol compound is preferable because the amount thereof is small, and among these, a bisphenol compound is preferable.

These compounds are disclosed, for example, in Japanese Examined Patent Publication Nos. 45-14039 and 5
It is disclosed in No. 1-29830. Specifically, 4-tert-butylphenol, 4-phenylphenol,
4-hydroxydiphenoxide, α-naphthol, β-
Naphthol, methyl-4-hydroxybenzoate, 2,
2'-dihydroxybiphenyl, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), 4,
4'-isopropylidene bis (2-methylphenol), 1,1-bis- (3-chloro-4-hydroxyphenyl) cyclohexane, 1,1-bis- (3-chloro-4)
-Hydroxyphenyl) -2-ethylbutane, 4,4'-
Secondary-isobutylidene diphenol, 4-hydroxybenzoic acid benzyl ester, 4-hydroxybenzoic acid-m-chlorobenzyl ester, 4-hydroxybenzoic acid β-phenethyl ester, 4-hydroxy-2 ',
4'-dimethylphenyl sulfone, 1-t-butyl-4
-P-hydroxyphenylsulfonyloxybenzene,
4-N-benzylsulfamoylphenol, 2,4-dihydroxybenzoic acid-p-methylbenzyl ester, 2,
Examples thereof include 4-dihydroxybenzoic acid-β-phenoxyethyl ester and 2,4-dihydroxy-6-methylbenzoic acid benzyl ester.

Among the diether compounds according to the present invention, the following general formula (II)
Those represented by are preferred.

In the above formula, R ₁ , R ₂ , R ₃ and R ₄ represent a hydrogen atom, an alkyl group having 6 or less carbon atoms, an alkoxy group or a halogen atom, and n represents an integer of 2 or more and 5 or less. R ₁ and R ₂ and R ₃ and R ₄ may combine with each other to form an aromatic ring.

In the general formula (II), R ₁ , R ₂ , R ₃ and R ₄ may be the same or different. Examples of these diether compounds are shown below.

Some of them are described in JP-A-60-56588, but specific examples include the following compounds.

1,4-di (4-methylphenoxy) butane mp.104 ° C 1,5-di (4-methylphenoxy) pentane mp.62 ° C 1,3-di (4-methylphenoxy) propane mp.93 ° C 1,4-di (4-Isopropylphenoxy) butane mp. 78
℃ 1,2-diphenoxyethane mp. 94 ℃ 1- (4-methylphenoxy) -2-phenoxyethane
mp.100 ° C 1- (4-chlorophenoxy) -2-phenoxyethane
mp. 101 ° C 1- (4-tert-butylphenoxy) -2-phenoxyethane mp. 92 ° C 1- (2-chlorophenoxy) -2-phenoxyethane
mp. 76 ° C 1,4-di (4-chlorophenoxy) butane mp. 104 ° C 1-naphthoxy (1) -2-phenoxyethane mp. 106 ° C 1,4-diphenoxybutane mp. 97 ° C 1- ( 4-Methylphenoxy) -2- (2-methylphenoxy) ethane mp. 85 ° C 1- (4-methylphenoxy) -2- (2,4-dimethylphenoxy) ethane mp. 70 ° C 1- (4-methylphenoxy)- 2- (3-methylphenoxy (ethane mp. 91 ° C 1- (4-fluorophenoxy) -2-phenoxyethane mp. 90 ° C 1- (3-methoxyphenoxy) -2-phenoxyethane mp. 66 ° C 1- (4-Fluorophenoxy) -2- (4-methylphenoxy) ethane mp. 106 ° C 1- (3-methoxyphenoxy) -2- (methylphenoxy) ethane mp. 62 ° C 1- (4-ethylphenoxy)- 2-phenoxy mp.106
° C 1- (4-ethoxyphenoxy) -2-phenoxyethane mp.123 ° C 1- (3-propylphenoxy) -2-phenoxyethane mp. 65 ° C 1,5-di (4-ethylphenoxy) pentane mp. 134 ° C. 1- (4-hexylphenoxy) -2-phenoxyethane mp. 78 ° C. Among the diether compounds according to the present invention, those having a melting point of 50 ° C. or more and 150 ° C. or less are preferable, and further 70 ° C. or more
Those having a melting point of 120 ° C. or less are particularly preferable.

The electron-donating colorless dye precursor and the electron-accepting compound of the present invention are separately dispersed together with a water-soluble polymer in a ball mill, a sand mill, an attritor, a triple roller mill, a pebble mill or the like. The diether compound of the present invention is similarly dispersed and added, or an electron-donating colorless dye precursor, or
It is possible to disperse and use the compound at the same time with the electron-accepting compound, but it is essential to disperse the compound at the same time as the electron-accepting compound in order to obtain a heat-sensitive recording material having high color density and high sensitivity, which is the object of the present invention. Is. That is, when the diether compound is dispersed alone, the coloring sensitivity is insufficient, and when it is dispersed simultaneously with the electron-donating colorless dye precursor, the sensitivity is similarly insufficient, and sufficient coloring sensitivity is obtained. It has been found that there is a drawback that fog is likely to occur.

The diether compound of the present invention is preferably dispersed at the same time as the electron-accepting compound. As a result, the dispersibility is good, sufficient sensitivity is obtained, and the fog is small. This effect is further exhibited by eutecticizing the electron-accepting compound and the diether compound in advance. However, when the diether compound and the electron-accepting compound are dispersed at the same time and the dispersed particle size is 3 μm or less, Since there is almost no difference from the melted one, a step such as eutectic is unnecessary, which is preferable.

Further, such a mixture and dispersion has an advantage that fog is less likely to occur than a eutectic one.

The mixing ratio of the diether compound of the present invention and the electron-accepting compound is 1: 5 to 3: 1 by weight. More preferably 1:
3 to 2: 1. If the proportion of the diether compound is smaller than this range, the effect of increasing the sensitivity is small, and if it is large, on the contrary, the saturation concentration is difficult to be obtained, and the storage stability of the color developing material is deteriorated.

The electron-donating colorless dye precursor is preferably used in a ratio of 1:10 to 2: 1 and further in a ratio of 1: 4 to 1: 1 with respect to the electron-accepting compound.

The dispersed electron-donating colorless dye precursor and the mixture of the electron-accepting compound and the diether compound are mixed in the above ratios, but additives are added to meet various requirements.

As an example of the additive, an oil absorbing substance such as an inorganic pigment is dispersed in a binder in order to prevent the recording head from being soiled at the time of recording, and a fatty acid is further added in order to enhance releasability to the head. , Metal soap, etc. are added. Therefore, generally, in addition to the color-developing agent and the color-developing agent, which directly contribute to color development, pigments, waxes, additives and the like are coated on a support to form a heat-sensitive recording material.

Specifically, the pigment is kaolin, calcined kaolin, talc,
It is selected from wax, diatomaceous earth, calcium carbonate, calcium hydroxide, magnesium hydroxide, magnesium carbonate, titanium oxide, barium carbonate, urea-formalin filler, cellulose filler and the like. Examples of waxes include paraffin wax, kauna barrow wax, microcrystalline wax, polyethylene wax, and higher fatty acid esters.

Examples of the metal soap include higher fatty acid polyvalent metal salts, that is, zinc stearate, aluminum stearate, calcium stearate, zinc oleate and the like.

As the binder used at the time of dispersion, polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyacrylic acid, Polyacrylic acid amide, starch derivative, casein, gelatin,
Examples include carboxymethyl cellulose and methyl cellulose.

In addition, at the time of dispersion, the dispersibility is often improved by adding a small amount of a surfactant or a water-soluble oligomer.

Further, a water-proofing agent (gelling agent, cross-linking agent) is added for the purpose of imparting water resistance to these binders, or emulsion of hydrophobic polymer, specifically, styrene-butadiene rubber latex, acrylic resin emulsion, etc. It can also be added.

The coating liquid is most commonly applied on a base paper, preferably a neutral paper.

Generally, the coating amount is ² to 10 g / m ² as a solid content, the lower limit is determined by the concentration at the time of color development by heating, and the upper limit is determined mainly by economic constraints.

(Examples of the Invention) Examples will be shown below, but the present invention is not limited to these examples.

Example (1) Preparation of Samples 1 to 8 2.5 g of 2-anilino-3-chloro-6-diethylaminofluorane, which is an electron-donating colorless dye precursor, and 2-anilino-3-methyl-6-N-methyl- 2.5 g of N-cyclohexylaminofluorane was dispersed together with 50 g of a 5% aqueous solution of polyvinyl alcohol (saponification number: 99%, polymerization degree: 1000) in a ball mill for 24 hours. On the other hand, 10 g of bisphenol A, which is also an electron-accepting compound, the diether compound shown in Table 1 and 10 g of a sensitivity improver used in the conventional heat-sensitive recording materials were dispersed together with 100 g of a 5% polyvinyl alcohol aqueous solution in a ball mill overnight.

After mixing these two kinds of dispersions, 20 g of kaolin (diiodia kaolin) was added to disperse well, and further, paraffin wax emulsion 30% dispersion liquid (Chukyo Yushi Hydrin P-7) and zinc stearate emulsion 30 %
Add 5 g of each dispersion (Chukyo Yushi Hydrin Z-7),
It was used as a coating liquid.

The coating solution was applied on neutral paper having a basis weight of 50 g / m ^{2 so} that the solid coating amount would be 6 g / m ² , dried at 60 ° C for 1 minute, and then applied with a super calender at a linear pressure of 60 kgW / cm. A coated paper was obtained.

(2) Preparation of Sample 9-11 In Sample 1, a sample having a large dispersed particle size was prepared by changing the dispersion time of the mixture of the electron-accepting compound and the diether compound to 3 hours, 6 hours, and 12 hours. The coated papers were prepared in the same manner as the above-mentioned.

(3) Preparation of sample 12 2.5 g of 2-anilino-3-chloro-6-diethylaminofluorane and 5 g of 1,2-diphenoxyethane were dispersed together with 50 g of a 5% aqueous solution of polyvinyl alcohol in a ball mill overnight to obtain an average particle size of 1.48. A μm dispersion was obtained. Similarly, 2-anilino-3-methyl-6-N-methyl-N-cyclohexylaminofluorane (2.5 g) and 1,2-diphenoxyethane (5)
g was dispersed to obtain a dispersion liquid having an average particle diameter of 2.31 μm. Bisphenol A (10 g) was dispersed with a 5% aqueous solution of polyvinyl alcohol (100 g) in a ball mill overnight. After mixing these three types of dispersions, coated paper was prepared in the same manner as in Samples 1 to 8.

(4) Preparation of Samples 13 to 15 In Samples 1 to 3, the bisphenol A and the diether compound were not simultaneously dispersed, but were separately dispersed with 50 g of a 5% polyvinyl alcohol aqueous solution and used.

(5) The coated paper was evaluated as follows.

(I) Printing sensitivity Using a Kyocera test tester, printing energy of 35 mJ / mm ²
Then, black solid printing was performed, and the density was measured with a Macbeth densitometer. Print density is 8dot / mm x 6dot / mm, pulse width / m
I went with s.

(Ii) Fog Measure the fog on the coated paper with a Macbeth densitometer and store it as a heat fog in an atmosphere of 60 ° C 30% RH for 24 hours.
The fog was similarly sought.

The results are shown in Table 1. The dispersed particle size shown in Table 1 indicates a volume average particle size, and is obtained by a particle size distribution measuring device (micro truck) manufactured by L & N Company.

In the column of dispersed particle diameter in Table 1, A is a volume average particle diameter of an electron-donating colorless dye, B is a diether compound, and C is an electron-accepting compound (bisphenol A).

In addition, the mixture of the diether compound and the electron-accepting compound is described as the volume average particle size of the mixture in both B and C terms.

Front page continuation (72) Inventor Ken Iwakura 210 Nakanuma, Minamiashigara-shi, Kanagawa Fuji Photo Film Co., Ltd. (56) References JP-A-60-56588 (JP, A) JP-A-59-190890 (JP, A) ) JP-A-59-101392 (JP, A) JP-A-59-159393 (JP, A)

Claims (1)

[Claims] 1. A thermosensitive recording obtained by coating a support with a coating liquid containing at least an electron-donating colorless dye precursor dispersed therein and a dispersion containing an electron-accepting compound dispersed therein. In the material, the dispersion liquid in which the electron-accepting compound is dispersed simultaneously contains a diether compound represented by the following general formula (I) as a dispersoid, and consists of the electron-accepting compound and the diether compound in the dispersion liquid. A heat-sensitive recording material, wherein the dispersed particles of the mixture have a volume average particle diameter of 3 μm or less. Ar ₁ -O-CnH ₂ n-O-Ar ₂ (I) In the above formula, Ar ₁ and Ar ₂ represent a substituted or unsubstituted aryl group, and n represents a positive integer of 10 or less.