JPH06191154A - Heat sensitive recording material - Google Patents

Abstract

PURPOSE:To make whiteness and sensitivity to color development of a heat sensitive recording material favorable, by a method wherein a colorless heat sensitive color development layer containing donating, color-developing dye precursor, a developer and 3,3'-diaminodiphenyl sulfone is provided on a substrate. CONSTITUTION:Fixed quantities each of a colorless, donating, color-developing dye precursor, accepting and developing compound and 3,3'-diaminodiphenyl sulfone are mixed into an aqueous solution such as polyvinyl alcohol, agitated and dispersed, through which a coating solution for a heat sensitive color developing layer is prepared. The coating solution is applied onto a substrate such as a plastic film, synthetic paper and a metallic foil and dried, to which a heat sensitive color development layer is laminated and a heat sensitive recording material which has high whiteness and is superior in sensitivity to color development is obtained. As an ideal example of a donating, color-developing dye precursor, 3-diethyl amino-6-methyl-7-aniline fluorene is available and as the ideal example of a color developing compound, 4,4'-bis(p-toluenesulfonamino carbonyl amino)diphenylmethane is available.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material. More specifically, the present invention relates to an extremely well-balanced heat-sensitive recording material having high whiteness and excellent color development sensitivity.

[0002]

2. Description of the Related Art A heat-sensitive recording material which forms a color image by utilizing a color development reaction of a colorless or light-colored electron-donating color-forming dye and a phenol or an organic acid is disclosed, for example, in JP-B-43-4160. It is disclosed in JP-B-45-14039 and JP-B-48-27736. In recent years, such a heat-sensitive recording material has various advantages such that a color image can be formed by simply heating it, and the recording apparatus can be made relatively compact. Is widely used, and the fields of application of heat-sensitive recording materials are diversifying.

With respect to these thermal facsimiles, thermal printers, and the like, improvements have been made in their apparatuses, and high-speed printing and high-speed image formation, which have been difficult in the past, are now possible. With the increase in the speed of such equipment, the thermal recording material used is required to have high recording sensitivity.

Therefore, conventionally, heat-fusible substances such as various fatty acid amides, their methylol compounds, methylene bis stearoamides, fatty acid amide compounds of ethylene bis stearoamide, and various fatty acid esters have been conventionally used in the thermosensitive coloring layer. It has been attempted to lower the melting points of the color-forming dye and the color-developing compound to increase the thermal sensitivity by adding.
However, the sensitivity is still insufficient to be applied when heat-sensitive color development is performed within a short time of a few milliseconds or 1 millisecond such as in high-speed facsimiles and high-speed printers developed one after another, or However, there is a problem that dust is adhered to the thermal head or sticking phenomenon occurs during printing for a long time, and the white paper develops background color over time.

Further, conventional heat-sensitive recording materials, which have weaknesses in storage stability of color images, are also required to have a great improvement in storage stability as their fields of use are diversified. The reason is that it is known that the color-developed image of the heat-sensitive recording material disappears over time, and this decolorization proceeds rapidly due to contact with oil or a plasticizer.

On the other hand, 4,4'-isopropylidenediphenol (hereinafter referred to as BPA) which has been conventionally used as a color-developing compound in order to satisfy the requirement for improving the preservability.
Has been proposed. B
PA is inexpensive and has relatively good sensitivity, but its storage stability for oils and plasticizers is not sufficient. As a material that replaces BPA, as a color-developing compound with excellent preservability and high whiteness,
4,4'-dihydroxydiphenyl sulfone, 4-hydroxy-4'-isopropyloxydiphenyl sulfone, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane and the like can be mentioned.
However, the sensitivity of these color-developing compounds having excellent storage stability and high whiteness is lower than that of BPA.

[0007] Examples of the use of the heat-sensitive recording material which is required to have improved storability include heat-sensitive recording type tickets for automatic ticket vending machines, use for coupons and commuter tickets, and heat-sensitive label paper for POS bar code system. , Long-term storage facsimile paper, word processor paper, CRT image printer paper, slip printer paper, etc. In these applications, excellent storability that does not cause decoloring even when exposed to harsh environments where oil and plasticizer adhere, and high sensitivity suitable for high-speed printing are also required. It has been said, however, that nothing completely satisfying them has been obtained.

[0008]

DISCLOSURE OF THE INVENTION The present invention is intended to solve these problems and to provide a thermosensitive recording material having a high whiteness and an excellent color-developing sensitivity, which is extremely well balanced.

[0009]

The present invention is directed to a colorless electron-donating color-forming dye precursor on a support, and an electron-accepting color-developing property which is brought into contact with the color-forming dye precursor to form a color upon heating. A thermosensitive recording material provided with a thermosensitive coloring layer containing a compound, wherein the thermosensitive coloring layer contains 3,3′-diaminodiphenylsulfone (melting point 168 ° C.). It was found that this could be solved, and further, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane (B-TU
By using M) as a color-developing compound, it was found that a heat-sensitive recording material excellent in oil resistance and preservability can be obtained, and the present invention was completed.

[0010]

The present inventors have studied various compounds in view of the above-mentioned object, and as a result, 3,3'-diaminodiphenyl sulfone has great compatibility with both color-forming dyes and color-developing compounds. It has been found that when this is added to a thermosensitive color-forming layer comprising a color-forming dye and a color-developing compound, the color-developing sensitivity shifts to the low temperature side, and thus a high-sensitivity thermosensitive recording material can be obtained. Further, the heat-sensitive recording material is generally manufactured by using water as a medium, and as a material for improving the color development sensitivity, the whiteness of the heat-sensitive recording material is likely to be lowered unless the material is hardly soluble in water. The 3,3'-diaminodiphenyl sulfone of the present invention is preferably insoluble in water and its powder is white. Further, although the reason is not clear, in the case of a heat-sensitive recording material using 3,3'-diaminodiphenyl sulfone, a color image is extremely fast against light and hardly discolored or erased, which is extremely preferable in practical use. Prior to the 3,3'-diaminodiphenyl sulfone of the present invention, a similar compound, 4,4'-diaminodiphenyl sulfone, is disclosed in JP-A-2-235682, but the effect of improving the coloring sensitivity is unsatisfactory. The object of the present invention to provide a thermal recording material which is sufficient and suitable for high speed printing cannot be achieved.

The amount of 3,3'-diaminodiphenyl sulfone used in the present invention is not particularly limited, but is generally 0.5 to 4 parts by weight per 1 part by weight of the color forming dye.
It is preferably 1 to 2 parts by weight, and similarly, the color-developing compound contained is preferably used in an amount of 0.5 to 4 parts by weight per 1 part by weight of the color forming dye.

The electron-donating color-forming dye precursor that constitutes the thermosensitive color-developing layer of the present invention can be selected from conventionally known ones. For example, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexylamino) -6-methyl-7-anilinofluorane, 3- [N-ethyl-N- (P-methylphenyl) amino] -6-methyl-7-anilinofluorane,
3- (N-ethyl-N-isopentyl) amino-6-methyl-7-anilinofluorane, 3-dibutylamino-
6-methyl-7-anilinofluorane, 3-dibutylamino-7-o-chloroanilinofluorane, 3-dipentylamino-6-methyl-7-anilinofluorane, 3
One or more selected from -diethylamino-7-m-trifluoromethylanilinofluorane and the like can be used.

The color-developing compound that constitutes the thermosensitive color-developing layer of the present invention can be selected from conventionally known compounds. For example, 4,4'-isopropylidene diphenol (bisphenol A), 4,4'-isopropylidene bis-
(2-methylphenol), 4,4'-isopropylidenebis- (2,6-di-tert-butylphenol), 4,4'-cyclohexylidenediphenol, 4
-Tert-butylphenol, 4-hydroxydiphenoxide, naphthol, β-naphthol, methyl-4-
Hydroxybenzoate, 4-hydroxyacetophenone, salicylic acid anilide, novolac type phenol resin, halogenated novolac type phenol resin, 4,4 ′
-Thiobis (3-methyl-6-tert-butylphenol), isopropyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, methylbenzyl p-hydroxybenzoate, oxalic acid, maleic acid, tartaric acid , Carboxylic acids such as citric acid, succinic acid, stearic acid, benzoic acid, p-tert
-Butylbenzoic acid, phthalic acid, gallic acid, salicylic acid,
3-isopropylsalicylic acid, 3,5-α-methylbenzylsalicylic acid, bis (hydroxyphenyl) sulfide, 1,7-bis (4-hydroxyphenylthio)-
3,5-dioxaheptane, p-nitrobenzoic acid, salts of these organic color-developing compounds with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel, 4,4 ′ -Dihydroxydiphenyl sulfone, 2,4-dihydroxydiphenyl sulfone, 3,3'-dihydroxydiphenyl sulfone, 3,
3'-diamino-4,4'-dihydroxydiphenyl sulfone, 3,3'-diallyl-4,4'-dihydroxydiphenyl sulfone, 3,3'-dichloro-4,4'-
Dihydroxydiphenyl sulfone, 4-hydroxydiphenyl sulfone, 4-hydroxy-4'-isopropyldiphenyl sulfone, 4-hydroxy-4'-isopropyloxydiphenyl sulfone, 4-hydroxy-4 '
-Benzyloxydiphenyl sulfone, 2,4-hydroxy-4'-methyldiphenyl sulfone, 3,4-hydroxyphenyl-p-tolyl sulfone, N- (o-toluoyl) -p-toluene sulfamide, N- (p- Toluenesulfonyl) -N'-phenylurea, 4,4'-bis (p-toluenesulfonylaminocarbonylamino)
It is composed of at least one member selected from diphenylmethane and the like.

Among them, as described above, from the viewpoint of excellent storability that does not cause decoloring even when exposed to a harsh environment where oil or plasticizer adheres, the particles contained in the thermosensitive coloring layer are excellent. As the color compound, 4,4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane is particularly preferable.

In the thermosensitive coloring layer of the present invention, a compound other than 3,3'-diaminodiphenylsulfone can be used as a heat-fusible substance (so-called sensitizer). As the heat-fusible substance that can be used together, a heat-fusible organic compound having a melting point of 50 to 150 ° C. is preferably used as long as the desired effect of the present invention is not impaired. Stearic acid amide, stearic acid methylol amide, 1-hydroxy-2-naphthoic acid phenyl ester, p-benzyl biphenyl, benzyl naphthyl ether, dibenzyl terephthalate, benzyl p-benzyloxybenzoate,
Diphenyl carbonate, ditolyl carbonate, m-terphenyl,
1,2-bis (m-tolyloxy) ethane, 1,5-bis (p-methoxyphenoxy) -3-oxapentane,
Diphenyl oxalate, bis (p-chlorobenzyl oxalate), bis (p-methylbenzyl oxalate), 1,4-
Bis (trioxymethoxymethyl) benzene, 1,2-
Examples thereof include di (3-methylphenoxy) ethane and 1,2-bis (3,4-dimethylphenoxy) ethane.

The heat-sensitive color forming layer used in the present invention preferably contains an adhesive and an inorganic pigment, and may further contain waxes if necessary. As the adhesive used in the present invention, polyvinyl alcohol having various molecular weights, starch and its derivatives, methoxycellulose,
Cellulose derivatives such as 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 Water-soluble polymer materials such as acid copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein, and polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, chloride Each latex such as vinyl / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, and styrene / butadiene / acrylic copolymer can be used.

The organic or inorganic pigments used in the thermosensitive coloring layer include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, calcined clay, talc, and Inorganic fine powder such as surface-treated calcium carbonate and silica,
Other examples include urea-formalin resin, styrene / methacrylic acid copolymer, and organic fine powder such as polystyrene resin. The amount of pigment used is adhesive 1
It is preferably added in the range of about 1 to 50 parts by weight with respect to parts by weight.

Further, the heat-sensitive color forming layer of the present invention may contain various waxes, if necessary. As the waxes, known waxes such as paraffin and metal salts of higher fatty acids can be used.

If desired, the thermosensitive coloring layer may be provided with an overcoat layer to improve sticking with the thermal head during printing. Further, the coating amount of the overcoat layer is not particularly limited, but generally 1 to
It is provided in the range of 20 g / m ² . Further, in the overcoat layer, it is possible to add a lubricant such as calcium stearate, zinc stearate, polyethylene wax, paraffin wax and ester wax, and an auxiliary agent such as a dispersant and a defoaming agent. Further, a curing agent such as glyoxal, an epoxy compound, boric acid, a dialdehyde starch, a methylol group-containing compound, or an isocyanate compound can be added for the purpose of improving water resistance.

The sheet-like support used in the heat-sensitive recording material of the present invention includes high-quality paper, medium-quality paper, single-glossy paper, medium-quality coated paper, slightly coated paper, coated paper, art paper, cast coated paper, Clear coated paper, resin laminated paper, etc. are generally used, but plastic film, synthetic paper, metal foil, etc., or a composite sheet in which these are combined can also be optionally used. At least one surface of such a sheet-like support is coated with a coating solution containing a mixture of the above-mentioned required components and dried to produce a heat-sensitive recording material. The coating amount is preferably 1 to 15 g / m ² in the dried state of the coating liquid layer, and particularly preferably ² to 10 g / m ² .

Further, a back layer for preventing blocking at the time of contact may be provided on the back surface of the heat-sensitive recording material obtained as described above, or a pressure-sensitive adhesive may be applied to form a heat-sensitive label. It is also possible to apply a magnetic layer to obtain a magnetic thermal paper.

The heat-sensitive recording material of the present invention thus obtained has high whiteness and excellent color-developing sensitivity.

[0023]

EXAMPLES The present invention will be specifically described below with reference to examples. Unless otherwise specified, "part" and "%" are
Represents "parts by weight" and "% by weight", respectively. Example 1 A thermal recording material was prepared by the following operation. Preparation amount of Dispersion A (parts) 3-dibutylamino-6-methyl-7-anilinofluorane 20 polyvinyl alcohol 10% liquid 10 water 70 The above composition was subjected to a sand grinder to give an average particle diameter of 1
It was pulverized to a size of μm.

Preparation amount of dispersion B Component (part) 4,4'-isopropylidenediphenol 20 Polyvinyl alcohol 10% liquid 10 Water 70 The above composition was subjected to a sand grinder and the average particle size was 1
It was pulverized to a size of μm.

Preparation amount of dispersion C (parts) 3,3'-diaminodiphenylsulfone 20 Polyvinyl alcohol 10% liquid 10 Water 70 The above composition was subjected to a sand grinder to give an average particle size of 1
It was pulverized to a size of μm.

Preparation of thermosensitive coloring layer 30 parts of the above-mentioned A solution, 60 parts of B solution, 60 parts of C solution, 60 parts of 50% calcium carbonate slurry, 15 parts of 30% zinc stearate dispersion, 100% aqueous solution of polyvinyl alcohol 100
The parts were mixed and stirred to obtain a thermosensitive color developing layer coating solution.

The heat-sensitive color forming layer coating solution thus obtained was added to 50
coating amount after drying on a high-quality paper g / m ² is coated to a 6.0 g / m ^2, and a heat-sensitive recording material was dried.

Example 2 The same operation as in Example 1 was performed. However, in forming the thermosensitive coloring layer, the following liquid D was used instead of liquid B. Preparation amount of Dispersion D (parts) 4-hydroxy-4'-isopropyloxydiphenylsulfone 20 Polyvinyl alcohol 10% liquid 10 Water 70 The above composition was subjected to a sand grinder to give an average particle size of 1
It was pulverized to a size of μm.

Example 3 The same operation as in Example 1 was performed. However, in forming the thermosensitive color developing layer, the following solution E was used instead of solution B. Preparation amount of dispersion E (parts) 4,4'-bis (p-toluenesulfonylamino carbonylamino) diphenylmethane 20 polyvinyl alcohol 10% liquid 10 water 70 The above composition was subjected to a sand grinder to give an average particle diameter of 1
It was pulverized to a size of μm.

Example 4 The same operation as in Example 1 was performed. However, in forming the thermosensitive coloring layer, the E liquid was used instead of the B liquid, and the following F liquid was used instead of the A liquid. Preparation amount of dispersion F (parts) 3-dipentylamino-6-methyl-7-anilinofluorane 20 polyvinyl alcohol 10% liquid 10 water 70 The above composition was subjected to a sand grinder to give an average particle diameter of 1
It was pulverized to a size of μm.

Example 5 The same operation as in Example 1 was performed. However, in forming the thermosensitive coloring layer, the solution E was used instead of the solution B, and the following solution G was used instead of the solution C. Preparation amount of Dispersion G Content (parts) 3,3′-diaminodiphenylsulfone 10 Bis (p-methylbenzyl) oxalate 10 Polyvinyl alcohol 10% liquid 10 Water 70 The above composition was subjected to a sand grinder to obtain an average particle diameter. Is 1
It was pulverized to a size of μm.

Comparative Example 1 The same operation as in Example 1 was performed. However, in forming the thermosensitive coloring layer, the following liquid H was used instead of liquid C. Preparation of Dispersion H Component (part) Bis (p-methylbenzyl oxalate) 20 Polyvinyl alcohol 10% liquid 10 Water 70 The above composition was subjected to a sand grinder to give an average particle diameter of 1
It was pulverized to a size of μm.

Comparative Example 2 The same operation as in Comparative Example 1 was performed. However, in forming the thermosensitive coloring layer, the liquid D was used instead of the liquid B.

Comparative Example 3 The same operation as in Comparative Example 1 was performed. However, in forming the thermosensitive coloring layer, the E liquid was used instead of the B liquid.

Comparative Example 4 The same operation as in Comparative Example 1 was performed. However, in forming the thermosensitive coloring layer, the solution E was used instead of the solution B, and C
Solution I was used instead of solution. Preparation of Dispersion I Amount (part) Stearic acid amide 20 Polyvinyl alcohol 10% liquid 10 Water 70 The above composition was subjected to a sand grinder to give an average particle size of 1
It was pulverized to a size of μm.

Comparative Example 5 The same operation as in Comparative Example 1 was performed. However, in forming the thermosensitive coloring layer, the solution E was used instead of the solution B, and C
Solution J was used instead of solution. Preparation amount of Dispersion J (parts) Methylolamide stearate 20 Polyvinyl alcohol 10% liquid 10 Water 70 The above composition was subjected to a sand grinder to give an average particle diameter of 1
It was pulverized to a size of μm.

The heat-sensitive recording material obtained by the above operation was tested. As for color development sensitivity, a commercially available heat-sensitive facsimile HIFAX-45 modified for testing was used, solid printing of 64 lines was performed with 1 line recording time of 5 msec, scanning line density of 8 dots / mm, and applied energy per dot of 0.3 mJ. The density was measured using a Macbeth reflection densitometer (RD-914 type, manufactured by Kollmorgen) and used as a representative value showing the color development sensitivity. Then, those having a concentration of 1.0 or more were evaluated as O, those having a concentration of 0.5 or more and less than 1.0 were evaluated as X, and those having a concentration of less than 0.5 were evaluated as XX.

As for the whiteness, a Hunter whiteness meter is used.
Measured with a blue filter. And this whiteness is 7
Those with 5 or more were evaluated as ◯, and those less than 75 were evaluated as x.

Further, Examples 3, 4, 5 and Comparative Example 3,
Regarding 4 and 5, regarding the image printed by the above method,
A storability test was conducted. In the storability test, the initial density of the image area of the thermal recording material was measured, and then this thermal recording material
After soaking in 0 ° C salad oil for 24 hours, the density of the image area was measured again, and the density preservation rate of the image area was 80% or more.
And However, the density preservation ratio of the image area was calculated and evaluated by the following formula. Concentration storage rate = [(concentration after storage stability test) / (initial concentration)] x 100 (%)

The evaluation results of sensitivity, whiteness and storability of each example are shown in Tables 1 and 2. As is clear from Tables 1 and 2, the thermosensitive recording material of the present invention has high whiteness and exhibits excellent color development sensitivity. Especially as a color-developing compound 4,
Even when 4'-bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane is used, high color development sensitivity suitable for high-speed printing is obtained, and the color is erased even when exposed to a severe environment such as immersion in oil. It showed excellent storability without causing it.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

According to the present invention, it is possible to provide a heat-sensitive recording material which has a high whiteness required for the heat-sensitive recording material and an excellent color-forming sensitivity which can be used in a wide variety of applications, and which is extremely balanced in terms of quality. did it.

Claims (2)

[Claims] 1. A thermosensitive color-forming layer containing a colorless electron-donating color-forming dye precursor on a support, and an electron-accepting color-developing compound which is brought into contact with the color-forming dye precursor to develop a color when heated. A heat-sensitive recording material provided with a heat-sensitive recording material comprising 3,3'-diaminodiphenyl sulfone in the heat-sensitive color forming layer. 2. An electron-accepting color-developing compound as 4,4 '.
2. The heat-sensitive recording material according to claim 1, which contains -bis (p-toluenesulfonylaminocarbonylamino) diphenylmethane.