JPH08310120A - Thermal recording material - Google Patents

Abstract

PURPOSE: To obtain a thermal recording material excellent in the long-term preservability of a recording image and not lowering the whiteness of a blank part by adding at least one kind of a ditosyl compd. represented by a specific formula to the thermal recording layer provided on a support of the thermal recording material as a storage stabilizer. CONSTITUTION: At least one kind of a ditosyl compd. represented by either one of formulae I, II (wherein n and m are an integer of 1-20) is added to the recording layer containing a leuco compd. and a coupler provided on a support to obtain a thermal recording material forming a recording image excellent in preservability, reducing the lowering of the whiteness of a blank part and capable of keeping a stable recording image. At least one kind of the ditosyl compd. is added to the recording layer in an amt. of 1-30%, pref., 3-20% by wt. of the total solid of the recording layer. The use ratio of the coupler to the leuco compd. is 0.5-50 pts.wt., pref., 1-10 pts.wt. per 1 pts.wt. of the leuco compd.

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 material, which is excellent in storage stability of recorded images, particularly long-term storage stability of recorded images under normal temperature and normal humidity, and is stable with little reduction in whiteness of white paper. The present invention relates to a thermosensitive recording medium that can maintain a recorded image.

[0002]

2. Description of the Related Art A heat-sensitive recording method using a normally colorless or slightly light-colored leuco compound and a coloring agent for coloring the leuco compound under heat does not require a developing step and is easy to maintain hardware. Therefore, it is widely used for recording for facsimiles, scientific measuring instruments, CD / ATM, POS labels and the like.

Along with the widespread use of thermosensitive recording media using leuco compounds, it is required to have not only high-speed recording suitability but also recorded image stability. Conventionally, attempts have been made to add various additives for the purpose of improving the storability of recorded images. For example, JP-A-49-45747 and JP-A-49-54040 propose the addition of various phenol derivatives.

However, in these conventional techniques, the effect of preventing the fading of the recorded image is not sufficient, the background is fogged, the fingerprint is erased when the fingerprint is attached to the colored portion, and the fingerprint is left on the uncolored portion. It has a defect that it develops color when it adheres, and is not practically usable.

Further, in JP-A-58-57990 and JP-A-58-87089, addition of a specific trisphenol compound is proposed. However, the improvement effect by this method is not sufficient, and it has been strongly desired to find a more effective method.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive material which is excellent in long-term storability of a recorded image at room temperature and normal humidity and which can maintain a stable recorded image with little reduction in whiteness of a white paper portion. To provide a recording body.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result, as a storage stabilizer in a recording layer containing a leuco compound and a color former on a support, By containing at least one ditosyl compound represented by the formula (1) or (2), excellent storability of recorded images, particularly long-term storability of recorded images under normal temperature and normal humidity and high temperature, and excellent whiteness It was possible to obtain a thermosensitive recording medium which can maintain a stable recorded image with a small decrease in whiteness.

Embedded image

[Chemical 4] (In formula, n and m represent the integer of 1-20.)

Regarding the thermosensitive recording medium using the ditosyl compound represented by the above general formulas (1) and (2), the effect of storage stability of recorded images is small in the accelerated test of high temperature and high humidity, but at room temperature and normal humidity. It was found that the recorded image of No. 1 has extremely excellent performance for long-term storage stability.

In the present invention, at least one ditosyl compound represented by the general formula (1) or (2) is 1 to 30% by weight, preferably 3 to 20% by weight based on the total solid content in the recording layer. If it is contained, the effect can be sufficiently obtained.

An example of the method for synthesizing the ditosyl compound in the present invention is shown below. Method for synthesizing n = 2 ditosyl compound of general formula (1) 11 A four-necked flask was charged with sodium hydroxide (60 g) and water (150 g) and dissolved, to which ethylene glycol (31.0 g) was added. Separately, p-toluenesulfonyl chloride (206.9 g) was added to dioxane (180 g).
And is added dropwise to the above flask over 2 hours. After completion of dropping, the mixture is stirred for 4 hours. The solvent was distilled off, and 1,2-dichloroethane (400 ml) and water (8
(00 ml) is added and the layers are separated. The aqueous layer was extracted with 1,2-dichloroethane (400 ml) and combined with the previous organic layer,
Wash with water (twice with 400 ml of water). The solvent was distilled off, and the residue was recrystallized from methanol / 1,2-dichloroethane to obtain the target ditosyl compound of the general formula (1) n = 2. Yield 94.1g. The melting point was 126-127 ° C.

As the leuco compound contained in the heat-sensitive recording layer in the heat-sensitive recording material of the present invention, those used in conventional heat-sensitive recording materials are used. Specifically, (1) triarylmethane compounds such as 3 , 3-bis (p-dimethylaminophenyl)
-6-Dimethylaminophthalide (Crystal Violet Lactone), 3- (p-Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl)
Phthalide, 3- (p-dimethylaminophenyl) -3-
(2-Phenylindol-3-yl) phthalide, 3,
3-bis (p-ethylcarbazol-3-yl) -3-
Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, etc .;

(2) Diphenylmethane compound For example, 4,4-bis-dimethylaminobenzhydrin benzyl ether, N-halophenylleuco auramine, N-2,4,5-trichlorophenyl leuco auramine and the like;

(3) Xanthene compound For example, rhodamine B-anilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-butylaminofluorane, 3-diethylamino-7- (2- Chloroanilino) fluoran, 3
-Diethylamino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-cyclohexyl- Methylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-chloro-7- (β-ethoxyethyl) aminofluorane, 3-diethylamino-6-chloro-7-
(Γ-chloropropyl) aminofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-
N-cyclohexyl-N-methylamino-6-methyl-
7-anilinofluorane, 3-diethylamino-7-phenylfluorane, 3- (N-isoamyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3-
Dibutylamino-6-methyl-7-anilinofluorane and the like;

(4) Thiazine-based compounds For example, benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and the like;

(5) Spiro compounds For example, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methylnaphtho- (3-methoxy-benzo) -spiropyran and the like; Furthermore, a mixture of these is used and is selected based on the properties desired depending on the application of the thermosensitive recording medium.

Examples of the color former combined with the leuco compound in the heat-sensitive recording layer include phenol derivatives,
Polyvalent metal salts such as aromatic carboxylic acid derivatives, N, N′-diarylthiourea derivatives, and zinc salts of organic compounds can be used. In particular,

4,4'-isopropylidene bisphenol, 4,4'-isopropylidene bis (o-methylphenol), 4,4'-secondary butylidene bisphenol, 4,4'-isopropylidene bis (2-tertiary) Butylphenol), 4,4′-cyclohexylidenediphenol, 4,4′-isopropylidenebis (2-chlorophenol),

2,2'-methylenebis (4-ethyl-6)
-Tert-butylphenol), 4,4'-butylidene bis (6-tert-butyl-2-methylphenol), 4,4'-diphenolsulfone, 4-isopropoxy-4'-hydroxyphenylsulfone, 4-benzyloxy- 4'-hydroxydiphenyl sulfone,
4,4'-diphenol sulfoxide, 2,2-bis (3-allyl-4-hydroxyphenyl) sulfone,

Isopropyl p-hydroxybenzoate, p
-Benzyl hydroxybenzoate, benzyl protocaquitenate, stearyl gallate, lauryl gallate, octyl gallate, 1,7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (4 −
Hydroxyphenylthio) -3-oxapentane, 1,
3-bis (4-hydroxyphenylthio) -propane,
1,3-bis (4-hydroxyphenylthio) -2-hydroxypropane, N, N′-diphenylthiourea,
N, N'-di (m-chlorophenyl) thiourea, salicylanilide, 5-chloro-salicylanilide,

2-hydroxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1-hydroxy-2-naphthoic acid, hydroxynaphthoic acid zinc, aluminum,
Metal salts such as calcium, bis (4-hydroxyphenyl) acetic acid methyl ester, bis (4-hydroxyphenyl) acetic acid benzyl ester, bis (4-hydroxyphenyl) acetic acid butyl ester,

1,3-bis (4-hydroxycumyl) benzene, 1,4-bis (4-hydroxycumyl) benzene, 2,4'-diphenol sulfone, 3,3'-diallyl-4,4 '-Diphenol sulfone, α, α-bis (4-hydroxyphenyl) α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S and the like are used.

In the heat-sensitive recording material of the present invention, the use ratio of the leuco compound and the coloring agent contained in the recording layer is not particularly limited, but is generally 0.5 per 1 part by weight of the leuco compound. -50 parts by weight, preferably 1
It is desirable to use about 10 to about 10 parts by weight of the coloring agent.

In the present invention, a heat-fusible substance can be used as a sensitizer. Specific examples of the heat fusible substance include:
Fatty acids such as stearic acid and behenic acid, stearic acid amide, p-benzylbiphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate,
β-benzyloxynaphthalene, β-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid phenyl ester, 1-hydroxy-2-naphthoic acid methyl ester, diphenyl carbonate, terephthalic acid dibenzyl ester, 1,4-dimethoxynaphthalene , 1,4-
Diethoxynaphthalene, 1,4-dibenzyloxoinaphthalene, 1,2-bis (phenoxy) ethane, 1,2
-(3-Methylphenoxy) ethane, 1,2-bis (4
-Methylphenoxy) ethane, 1,4-bis (phenoxy) butane, 1,4-bis (phenoxy) -2-butene, dibenzoylmethane, 1,4-bis (phenylthio) butane, 1,4-bis (phenylthio) ) -2-Butene,

1,3-bis (2-vinyloxyethoxy) benzene, 1,4-bis (2-vinyloxyethoxy) benzene, p- (2-vinyloxyethoxy) biphenyl, p-aryloxybiphenyl, p- Propargyloxybiphenyl, dibenzoyloxymethane,
1,3-dibenzoyloxypropane, dibenzyl disulfide, 1,1-diphenylethane, 1,1-diphenylpropanol, p- (benzyloxy) benzyl alcohol, 1,3-diphenoxy-2-propanol,
N-octadecylcarbonyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, etc. are used.

In the paint for forming the heat-sensitive recording layer,
Polymer resins used as binders include starch and its derivatives, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose and ethyl cellulose, polyvinyl alcohol, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymers. Polymer, acrylamide / acrylic acid ester /
Methacrylic acid copolymer, styrene-maleic anhydride copolymer alkali salt, isobutyl-maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate,
Water-soluble polymers such as gelatin and casein,

Further, polyvinyl acetate, polyurethane, polyacrylic acid ester, polymethacrylic acid ester, vinyl chloride, vinyl acetate copolymer, aqueous emulsion of ethylene / vinyl acetate copolymer, styrene / butadiene copolymer, styrene. -A water-dispersible polymer such as a latex made of a butadiene-acrylic copolymer is used.

In the paint for forming the heat-sensitive recording layer, there are further added usual auxiliary components such as pigments, dispersants,
Of course, a lubricant, a surfactant, a fluorescent dye, a coloring dye, an ultraviolet absorber, and the like can be used in combination, and specific examples thereof include calcium carbonate, silica, zinc oxide, and titanium oxide as pigments. , Aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, inorganic fine powder such as surface-treated calcium and silica, organic fine powder such as urea-formalin resin, styrene-methacrylic copolymer, polystyrene resin In addition to the above water-soluble binder, surfactants such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, and sodium lauryl alcohol sulfate / sodium can be used as pigments and dispersants such as powders.

As a method for adjusting these substances into a coating liquid for a recording layer, generally, a wet pulverizer such as an attritor or a sand grinder is used with water as a dispersion medium.
It is prepared by dispersing so as to have an average particle diameter of about μm, and measuring and mixing each component so as to have a necessary mixing ratio.

The support used in the present invention is not particularly limited and includes, for example, high-quality paper, recycled paper, single-glossy paper, oil-resistant paper, coated paper, art paper, cast coated paper, lightly coated paper, resin laminated paper. Polyolefin synthetic paper, synthetic fiber paper, synthetic resin film and the like can be used as appropriate.

Further, in the heat-sensitive recording material of the present invention, an intermediate layer containing an inorganic pigment and a binder as a main component is provided between the support and the heat-sensitive recording layer, if necessary, and further on the heat-sensitive recording layer. It is also possible to provide an overcoat layer on the above and further to provide a backcoat layer on the opposite surface of the support for curl adjustment and the like.

As a method for forming the recording layer on the support, a known coating machine such as an air knife coater, various blade coaters, roll coaters and curtain coaters can be used, and the coating amount of the recording layer is not particularly limited. ² to 12 g / m < ² >, preferably 3 to 10 g / m < ² > on a dry weight basis.
It is applied in the range of about ² . Smoothing with a super calendar after coating is also effective in improving image quality.

[0032]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, "part" and "%" in an example show "weight part" and "weight%", respectively, unless there is particular notice.

Example 1 Liquid A Preparation Compound 1 (compound of n = 2 in Chemical Formula 1) 10 parts 20% Polyvinyl alcohol (Kuraray Poval 105, manufactured by Kuraray) 10 parts Water 20 parts This composition was sand milled to give an average particle diameter. (Horiba Seisakusho's Laser Diffraction / Scattering Particle Size Analyzer [LA91
0] is the median diameter determined in [0]. same as below. ) Is 1.5
It was pulverized until it became μm. Liquid B Preparation 3-dibutylamino-6-methyl-7-anilinofluorane 10 parts 20% polyvinyl alcohol (same as above. The same below) 10 parts water 20 parts This composition was sand milled to have an average particle size of 0.8 μm. Crushed until Preparation of liquid C 4,4′-isopropylidene bisphenol 10 parts 20% polyvinyl alcohol 10 parts water 20 parts This composition was ground with a sand mill until the average particle size became 1.5 μm. Liquid D Preparation Metaterphenyl 10 parts 20% Polyvinyl alcohol 10 parts Water 20 parts This composition was ground with a sand mill until the average particle size became 1.5 μm. Formation of thermosensitive recording layer A solution 20 parts, B solution 40 parts, C solution 80 parts, D solution 80 parts, 2
0% polyvinyl alcohol 60 parts, calcium carbonate 35
Parts, 30 parts of a 30% zinc stearate dispersion liquid (D-523, Chukyo Yushi) and 50 parts of water were mixed and stirred to obtain a heat-sensitive recording layer coating liquid. The obtained coating liquid was applied onto a high-quality paper of 50 g / m ^{2 so} that the dry weight was 4 g / m ^2, and dried.

Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the compound 2 (a compound of m = 2 in the chemical formula 2) was used in place of the compound 1 in the preparation of the liquid A in Example 1.

Example 3 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that Compound 3 (a compound of m = 3 in the chemical formula 2) was used in place of Compound 1 in the preparation of solution A in Example 1.

Example 4 Heat sensitivity was the same as in Example 1 except that 4-hydroxy-4'-isopropoxy-diphenyl sulfone was used in place of 4,4'-isopropylidene bisphenol in the preparation of the liquid C of Example 1. I got a record.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the liquid A was not used in the formation of the thermosensitive recording layer of Example 1.

Comparative Example 2 In the preparation of solution A of Example 1, instead of compound 1, 4,
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 4'-thiobis (6-tert-butyl-meta-cresol) was used.

Comparative Example 3 In the preparation of solution A of Example 1, instead of compound 1, 2,
A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 2'-methylenebis (4-methyl-6-tert-butylphenol) was used.

Comparative Example 4 In the preparation of solution A of Example 1, 1, instead of compound 1,
A thermal recording material was obtained in the same manner as in Example 1 except that 1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane was used.

Comparative Example 5 In the preparation of solution A of Example 1, 1, instead of compound 1,
Example 1 except that 1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane was used.
A thermosensitive recording medium was obtained in the same manner as described above.

The following 9 evaluation tests were conducted on the 9 kinds of thermal recording materials obtained as described above, and the results are shown in Table 1. Color density (substitute characteristic of recording sensitivity) Commercially available GIII facsimile machine FACOM FAX 6
21C (Fujitsu Limited) recording power 0.90 W / do
Printing was performed under the conditions of t, energization time 0.45 msec, and cycle about 5 msec / l, and the recorded image density and background density at the time of printing were measured by a Macbeth densitometer (RD-914 type, manufactured by Macbeth Co.). High-temperature and high-humidity accelerated storage test A thermosensitive recording material with printed color is stored for 24 hours under the conditions of a temperature of 50 ° C and 60% RH, and the color density and background density of the recorded image after storage are measured by a Macbeth densitometer (RD-914 type). ). The residual rate was determined from the recorded image density before and after storage. Residual rate (%) = 100 x (recorded image density after storage) / (recorded image density before storage) Normal temperature and normal humidity storage test 7 When the thermosensitive recording material with printed color was filed in an air-conditioned office 7 Stored for a year, the color density and background density of the recorded image after storage are measured by Macbeth densitometer (RD-914
Type). The residual rate was calculated from the color density of the recorded image before and after storage. Residual rate (%) = 100 x (recorded image density after storage) / (recorded image density before storage)

[0043]

[Table 1]

[0044]

As is clear from the results of Table 1, the thermosensitive recording medium obtained in the present invention was a thermal recording medium excellent in long-term storage stability of recorded images under normal temperature and normal humidity.

Claims (1)

[Claims] 1. A thermosensitive recording medium comprising a support and a recording layer containing a leuco compound and a color-forming agent, which is represented by the general formula (1) or (2) as a storage stabilizer in the thermosensitive recording layer. A heat-sensitive recording material containing at least one ditosyl compound. Embedded image Embedded image (In formula, n and m represent the integer of 1-20.)