JPH04353490A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material improved in background fog and the preservability of a recording image under high temp. environment and the, stability of the recording image against machine oil in a well-balanced state by together using a specific citric ester compound in a color forming system containing a specific basic dye and a developer. CONSTITUTION:In a thermal recording material wherein a recording layer containing a colorless-light-colored basic dye and a developer is provided on a support, the recording layer contains at least one kind of 3-diethylamino-7-(o- chlorophenylamino)fluorane and/or 3-di(n-butyl)amino-7-(o-chlorophenylamino) fluorane as the basic dye and at least one kind of 4-hydroxydiphenylsulfone compound with an m.p. of 120 deg.C or higher as the developer and further contains 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate and/or a metal salt thereof.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording medium, and more particularly to a heat-sensitive recording medium that exhibits excellent background fog and storage stability of recorded images in high-temperature environments.

0002

[Prior Art] Conventionally, heat-sensitive recording materials have been well known, which utilize a coloring reaction between a colorless or light-colored basic dye and a coloring agent, and obtain a recorded image by causing the two coloring substances to react with heat. ing. Such heat-sensitive recording media are used in a wide range of fields because they are relatively inexpensive, and the recording equipment is compact and maintenance-free.

[0003] As an example, recently, POS (point
Label systems have come to be used in various manufacturing processes, and they do not cause background fog even when used in places where the environmental temperature is around 90 degrees Celsius, and even in such environments, the recorded image remains unchanged. There is a growing demand for thermosensitive recording media with good storage stability.

However, heat-sensitive recording materials generally have a problem with the storage stability of recorded images, and particularly under high temperature conditions, the recorded images fade in a relatively short period of time. In order to improve the storage stability of such recorded images, methods using various stabilizers have been proposed, but stabilization is relatively effective in improving the storage stability of recorded images at high temperatures. Even if the agent is used as an agent, it is not sufficiently effective in preventing fading of recorded images due to machine oil, etc., and cannot be applied to heat-sensitive recording bodies used in manufacturing processes in high-temperature environments and in contact with machine oil.

[0005]

[Problems to be Solved by the Invention] In view of the current situation, the present inventors have developed a material that does not cause skin fogging even when exposed to an environmental temperature of around 90°C, and has a sufficient density even in such a high temperature environment. In order to obtain a heat-sensitive recording material that can maintain a recorded image and has excellent stability of the recorded image against mechanical oil, a wide range of studies were conducted on the components constituting the recording layer. As a result, they discovered that the desired thermosensitive recording material could be obtained by using a specific phosphoric acid ester compound in combination with a specific basic colorless dye and coloring agent, and thus completed the present invention.

[0006]

[Means for Solving the Problems] The present invention provides, on a support,
In a thermosensitive recording material provided with a recording layer containing a colorless or light-colored basic dye and a coloring agent, 3-diethylamino-7-(o-chlorophenylamino)fluoran and/or 3-diethylamino-7-(o-chlorophenylamino)fluoran and/or -di(n-butyl)
Amino-7-(o-chlorophenylamino)fluoran contains at least one 4-hydroxydiphenylsulfone compound having a melting point of 120°C or higher as a coloring agent, and 2,2'-methylenebis(4,6-di -te
rt-butylphenyl) phosphate and/or 2,
This is a heat-sensitive recording material characterized by containing a metal salt of 2'-methylenebis(4,6-di-tert-butylphenyl)phosphate.

[0007]

[Function] As described above, the present invention improves the storage stability of recorded images by using a specific phosphoric acid ester compound in combination with a coloring system containing a specific basic dye and a coloring agent. The present invention provides a heat-sensitive recording material in which the stability of recorded images against machine oil is improved in an extremely well-balanced manner.

[0008] The 4-carbon having a melting point of 120°C or higher used in the present invention
Specific examples of hydroxydiphenylsulfone compounds include 4-hydroxy-4'-methyldiphenylsulfone,
4-Hydroxy-4'-isopropoxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone, 4
, 4'-dihydroxydiphenylsulfone, bis(3-
Allyl-4-hydroxyphenyl) sulfone, 4-hydroxy-3',4'-tetramethylene diphenyl sulfone, 4-hydroxy-3',4'-trimethylene diphenyl sulfone, etc. Two or more types can also be used in combination. Among the above 4-hydroxydiphenylsulfone compounds, 4-hydroxy-4'-isopropoxydiphenylsulfone and 4-hydroxydiphenylsulfone
Hydroxy-3',4'-tetramethylene diphenyl sulfone not only provides a highly sensitive heat-sensitive recording medium, but also
In combination with a phosphate ester compound used together,
This is preferred because a heat-sensitive recording material having particularly excellent resistance to recorded images against high temperatures and machine oil can be obtained.

In the present invention, the ratio of the specific basic dye and coloring agent used is not particularly limited, but the specific coloring agent is preferably used in an amount of 50 parts by weight per 100 parts by weight of the basic dye. ~1000 parts by weight, more preferably 1
It is desirable to adjust the amount to be in the range of 50 to 700 parts by weight.

Furthermore, in the present invention, 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate and/or or 2,2'-methylenebis(4,6
Metal salts of -di-tert-butylphenyl) phosphate are used in combination, and metals constituting such metal salts include, for example, sodium, zinc, magnesium, barium, calcium, aluminum, tin, titanium,
Examples include nickel, cobalt, manganese, and iron. Of course, it can also be used as a mixture of two or more metal salts. The amount of these phosphoric acid ester compounds to be used is not particularly limited, but is generally about 1 to 300 parts by weight per 100 parts by weight of the coloring agent.
Preferably, the range is about 1 to 100 parts by weight.

As mentioned above, in the present invention, at least one of 3-diethylamino-7-(o-chlorophenylamino)fluoran or 3-di(n-butyl)amino-7-(o-chlorophenylamino)fluoran is treated with a basic dye. However, other known basic dyes may be used as long as they do not impede the effects of the present invention, such as JP-A-2-2
Triarylmethane dyes, diphenylmethane dyes, divinylphthalide dyes, thiazine dyes, spiro dyes, lactam dyes, fluoran dyes, fluorene dyes, etc. as described in Japanese Patent No. 39977 can also be used in combination. In addition, when using other basic dyes together, the proportion of other basic dyes in the total basic dyes is 20% by weight.
It is desirable to adjust it so that it is as follows.

[0012] Furthermore, in the present invention, 4-
Hydroxydiphenyl sulfone is used as a coloring agent, but within a range that does not impede the effects of the present invention, for example,
It is also possible to use various known coloring agents such as those described in JP-A-239977.

In the heat-sensitive recording material of the present invention, a known thermofusible substance may also be used in combination for the purpose of improving recording sensitivity. Examples of such thermofusible substances include fatty acid amides such as stearic acid amide, stearic acid methylene bisamide, stearic acid ethylene bisamide, stearic acid methylolamide, oleic acid amide, palmitic acid amide, coconut fatty acid amide, p-benzyl biphenyl, 1,2-bis(phenoxy)ethane, 1
, 2-bis(4-methylphenoxy)ethane, 1,2-
(3-methylphenoxy)ethane, 1-(4-methoxyphenoxy)-2-(2-methylphenoxy)ethane,
Ethers such as 2-naphthol benzyl ether and benzyl-4-methylthiophenyl ether, esters such as dibenzyl terephthalate and 1-hydroxy-2-naphthoic acid phenyl ester, 2,2'-methylene bis(
4-methyl-6-tert-butylphenol), 2,
2'-methylenebis(4-ethyl-6-tert-butylphenol), 2,2'-methylidenebis(4,6-
di-tert-butylphenol), 2,2'-ethylidenebis(4-sec-butyl-6-tert-butylphenol), 4,4'-butylidenebis(6-te
rt-butyl-3-methylphenol), 4,4'-thiobis(6-tert-butyl-3-methylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butyl phenyl)butane, 1,1,3
-Tris(5-cyclohexyl-4-hydroxy-2-
methylphenyl)butane, 1,3,5-tris[2-(
3,5-di-tert-butyl-4-hydroxycinnamoyloxy)ethyl isocyanurate, 1,3,5
-Tris(4-tert-butyl-3-hydroxy-2
, 6-dimethylbenzyl) isocyanurate, tris(
3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 2,4,6-tris(3',5
'-di-tert-butyl-4'-hydroxybenzyl) mesitylene, pentaerythrityl-tetrakis [3-
(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and other hindered phenols;
Examples include ultraviolet absorbers such as 2-hydroxy-4-benzyloxybenzophenone. Among them, the melting point is 95℃
The above are preferred.

[0014] Coating liquids containing these materials are generally prepared by using water as a dispersion medium and using a stirring/pulverizing machine such as a ball mill, an attritor, a vertical or horizontal sand mill, or a colloid mill to remove dyes, coloring agents, and phosphate ester compounds. etc. are prepared by dispersing them together or separately. Such coating liquids usually contain starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, sulfone group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, Various modified polyvinyl alcohols such as silicone-modified polyvinyl alcohol, styrene/maleic anhydride copolymer salts, styrene/acrylic acid copolymer salts, styrene/butadiene copolymer emulsions, etc. are preferably 2 to 40% by weight of the total solid content. is 5~
It is blended in an amount of about 25% by weight. Of course, two or more types of these binders can also be used in combination.

Furthermore, various auxiliary agents can be added to the coating solution, such as dioctylsulfosuccinic acid sodium salt, dodecylbenzenesulfonic acid sodium salt,
Dispersants such as sodium lauryl alcohol sulfate ester and fatty acid metal salts, ultraviolet absorbers such as benzophenone, cyanoacrylate, and hydroxybenzoate,
Other examples include antifoaming agents, fluorescent dyes, and colored dyes.

[0016] In order to prevent the thermal recording medium from causing sticking due to contact with a recording device or a recording head, stearate wax, polyethylene wax, carnauba wax, microcrystalline wax, or
Dispersions or emulsions of carboxy-modified paraffin wax, zinc stearate, calcium stearate, etc. can also be added.

In addition, kaolin, clay, talc, calcium carbonate,
Magnesium carbonate, calcined clay, titanium oxide, diatomaceous earth,
Inorganic pigments such as fine particulate anhydrous silica and activated clay, organic pigments such as styrene microballs, nylon powder, polyethylene powder, urea/formalin resin filler, and raw starch granules can also be added.

In the heat-sensitive recording material of the present invention, the method for forming the recording layer is not particularly limited, and it can be formed according to well-known and commonly used techniques. Examples include a method of forming a recording layer by coating with a suitable coating device such as a knife coater, blade coater, bar coater, die coater, gravure coater, curtain coater, etc. and drying.

[0019] Furthermore, the amount of coating liquid applied is not particularly limited, and is generally 1.0 to 12 g/m in terms of dry weight.
2, preferably adjusted within the range of 1.5 to 10 g/m2. Paper, plastic film, synthetic paper, etc. can be used as the support, but paper is preferable in terms of cost and coating suitability, and synthetic paper is preferably used in consideration of color density.

[0020] The heat-sensitive recording material of the present invention thus obtained is as follows:
Because a specific phosphoric acid ester compound is used in combination with a coloring system containing a combination of a specific basic dye and a coloring agent, there is extremely little reduction in whiteness or recording density even when exposed to high temperature conditions. Moreover, it exhibits an excellent property in that there is almost no decrease in recording density even when it comes into contact with machine oil. In addition, in the present invention, it is also possible to provide a protective layer on the front and/or back surface of the heat-sensitive recording material, or to provide an intermediate layer between the support and the heat-sensitive recording layer, and to further apply adhesive processing. Various known techniques in the field of heat-sensitive recording material manufacturing can be added.

[0021]

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is of course not limited to these. Further, unless otherwise specified, parts and percentages in the examples indicate parts by weight and percentages by weight, respectively.

Example 1 ■ Formation of intermediate layer Calcined clay (trade name: Ansilex, manufactured by EMC) 100 parts Styrene-butadiene copolymer latex (solid content: 50%)
15 parts 10% polyvinyl alcohol aqueous solution
30 parts water


A coating solution for an intermediate layer was prepared by mixing 200 parts of the above composition. The obtained coating liquid was applied onto a 50 g/m2 high-quality paper so that the coated amount after drying was 7 g/m2, and dried to form an intermediate layer.

■Preparation of liquid A 3-di(n-butyl)amino-7-(o-chlorophenylamino)fluoran


10 parts 5% methylcellulose aqueous solution

Part 10 Water


10 parts of this composition was sand milled to an average particle size of 0.
It was ground to 8 μm. ■ Preparation of B solution 4-hydroxy-4'-isopropoxydiphenylsulfone 35 parts 2,2'-methylenebis(4,6-di-tert-butylphenyl)
Mixture of sodium phosphate and magnesium silicate (trade name: Adeka Arcles F-85,
Manufactured by Asahi Denka Kogyo Co., Ltd.)
15 parts
5% methylcellulose aqueous solution

50 parts water

40 parts of this composition was ground in a sand mill until the average particle size was 1.4 μm. (2) Formation of heat-sensitive recording layer 30 parts of liquid A, 140 parts of liquid B, 160 parts of a 10% polyvinyl alcohol aqueous solution, 35 parts of calcium carbonate, and 100 parts of water were mixed and stirred to obtain a coating liquid for a heat-sensitive recording layer. The resulting coating liquid was coated onto the intermediate layer to a dry weight of 7 g/m 2 and dried to obtain a heat-sensitive recording material.

Example 2 In preparing solution A, 3-di(n-butyl)amino-7-
(o-chlorophenylamino) instead of fluorane
-diethylamino-7-(o-chlorophenylamino)
The same procedure as in Example 1 was carried out except that fluoran was used and 4-hydroxy-3',4'-tetramethylene diphenyl sulfone was used instead of 4-hydroxy-4'-isopropoxydiphenyl sulfone in the preparation of Solution B. A thermosensitive recording medium was obtained.

Comparative Example 1 In preparing liquid B, 2,2'-methylenebis(4,6-
Thermal reaction was carried out in the same manner as in Example 1, except that 15 parts of 4-hydroxy-4'-isopropoxydiphenyl sulfone was used instead of 15 parts of the mixture of sodium salt of di-tert-butylphenyl) phosphate and magnesium silicate. Obtained a record.

Comparative Example 2 In preparing liquid B, 2,2'-methylenebis(4,6-
Same as Example 2, except that 15 parts of 4-hydroxy-3',4'-tetramethylene diphenyl sulfone was used instead of 15 parts of the mixture of sodium salt of di-tert-butylphenyl) phosphate and magnesium silicate. A thermosensitive recording material was obtained.

Comparative Example 3 In preparing liquid A, 3-di(n-butyl)amino-7-
3-(N-ethyl-N-isoamyl)amino-6 instead of 10 parts of (o-chlorophenylamino)fluorane
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 10 parts of -methyl-7-phenylaminofluorane was used.

Comparative Example 4 In the preparation of Solution B, 4,4'-
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 35 parts of isopropylidene diphenol was used.

Comparative Example 5 In preparing liquid B, 2,2'-methylenebis(4,6-
1-[α-methyl-α-(4′-hydroxyphenyl)ethyl]-4-[α′,α′ - except that 15 parts of bis(4″-hydroxyphenyl)ethyl]benzene was used.
A thermosensitive recording material was obtained in the same manner as in Example 1.

The seven types of heat-sensitive recording materials obtained were tested using a Matsushita simulator MF-1 (applied voltage 16 V, pulse width 5 ms).
) was recorded. The density of the obtained recorded image and the density of the background area were measured using a Macbeth densitometer (model RD-914, manufactured by Macbeth Co., Ltd.), and the results are shown in Table 1.

Next, the recorded heat-sensitive recording medium was treated in a hot air dryer at 95° C. for 5 hours, and the density of the recorded image and the density of the background were measured using a Macbeth densitometer. The storage stability and background fog were evaluated, and the results are also listed in Table 1.

[0032] Also, machine oil was applied to the surface of the recording layer of the heat-sensitive recording material after recording, and after leaving it for two weeks at room temperature, the state of disappearance of the recorded image was visually evaluated, and the results were evaluated. It is listed in Table 1. [Evaluation Criteria] ○: Almost no disappearance of the recorded image is observed. △: The recorded image has largely disappeared, but is barely legible. ×: Most of the recorded image has disappeared and cannot be read.

[0033]

[Table 1]

[0034]

Effects of the Invention As is clear from the results in Table 1, the heat-sensitive recording material of the present invention exhibits extremely little decrease in whiteness and recording density even when exposed to high temperature conditions, and has stable storage stability of recorded images against machine oil. It also exhibited excellent properties in terms of performance.

Claims (1)

[Claims] 1. A heat-sensitive recording material comprising a recording layer containing a colorless or light-colored basic dye and a coloring agent on a support, in which 3-diethylamino-7-( o-chlorophenylamino)fluoran and/or
or 3-di(n-butyl)amino-7-(o-chlorophenylamino)fluoran as a coloring agent with a melting point of 12
Contains at least one type of 4-hydroxydiphenylsulfone compound having a temperature of 0°C or higher, and 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate and/or 2,2'-methylenebis(4 ,6
1. A heat-sensitive recording material comprising a metal salt of -di-tert-butylphenyl) phosphate.