JP3273152B2 - Thermal recording material - Google Patents

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 utilizing a color development reaction between a leuco dye and a color developer, and more particularly to a heat-sensitive recording material having water resistance, heat resistance and light resistance.

[0002]

2. Description of the Related Art A thermosensitive recording material generally comprises a support such as paper, synthetic paper, plastic film and the like, on which a thermosensitive coloring layer mainly composed of a coloring composition is provided. A colored image can be obtained by heating with light or a strobe lamp. Compared to other recording materials, this type of heat-sensitive recording material can be recorded in a short time with a relatively simple device without performing complicated processing such as development and fixing.
Due to its advantages such as low noise, low environmental pollution, and easy cost, it is widely used as a recording material in various fields such as computers, facsimile machines, ticket vending machines, labels, recorders, etc. It's being used. A thermochromic composition used in such a thermosensitive recording material generally comprises a color former and a developer that causes the color former to develop color when heated, and examples of the color former include a colorless color having a lactone, lactam or spiropyran ring. Alternatively, a light-colored leuco dye has been used, and an organic acid or a phenolic substance has been used as a developer. The recording material in which the color former and the developer are combined has the advantages that the obtained image has a sharp image tone, that the background has a high whiteness, and that the image has excellent weather resistance. Have.

However, when this thermosensitive recording material is immersed in water, the image area loses its color. When used at a high room temperature, the background color develops. It has various drawbacks, such as discoloration of parts. Therefore, countermeasures such as providing a protective layer (overcoat layer) on the heat-sensitive coloring layer have been taken, but there is still room for improvement in fading of images due to water or light, and background coloring due to heat. . Further, in recent years, high-speed printing using these heat-sensitive recording materials has been desired, and good heat responsiveness, that is, higher sensitivity has been further required.

[0004] From such a viewpoint, in terms of materials,
Waterfastness, lightfastness, heat resistance, and a developer with good sensitivity have been studied, but one that satisfies these characteristics has not been found, and as one of relatively excellent ones, There are 4-hydroxy-diphenylsulfonic acid derivatives. It has good water resistance, heat resistance, and sensitivity, but has the disadvantage of causing fading of printed images due to light, and does not have sensitivity enough to cope with high-speed dictation. On the other hand, as a sensitizer, at least one of oxalic acid esterified electric materials, in particular, di (p-methylbenzyl) oxalate, di (p-chlorobenzyl) oxalate, and dibenzyl oxalate is used as the sensitizer. By using in combination, the present inventors have confirmed that the sensitivity can be improved without lowering the water resistance and heat resistance, but the coating property and the life of the coating liquid, that is, aggregation occurs with time. There are drawbacks. In order to improve the light resistance, there is a method of adding an ultraviolet absorber to the overcoat layer, the thermosensitive coloring layer or the undercoat layer, but the effect is not satisfactory.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above points, and is not limited to water resistance and heat resistance.
In particular, it has excellent light fastness and long life of the color layer coating solution.
Moreover, it is an object to obtain a heat-sensitive recording material having high sensitivity.

[0006]

According to the present invention, there is provided a thermosensitive recording material having a thermosensitive coloring layer containing a leuco dye, a color developer and a sensitizer on a support.
Hydroxy-4'-isopropoxydiphenyl sulfone, di (p-methylbenzyl) oxalate as a sensitizer,
At least one of di (p-chlorobenzyl) oxalate and dibenzyl oxalate is used, and dihydroxybenzophenone, 4,4'-dihydroxydiphenylsulfone and 2,2'-dimethyl-
There is provided a heat-sensitive recording material containing at least one of 4,4'-dihydroxydiphenyl sulfone. Hereinafter, the present invention will be described in detail.

As described above, in the heat-sensitive recording material of the present invention, 4-hydroxy-4'-isopropoxydiphenyl sulfone, which is excellent in water resistance, heat resistance and sensitivity, is used as a color developing agent. Since at least one of di (p-methylbenzyl) oxalate, di (p-chlorobenzyl) oxalate and dibenzyl oxalate is used as a sensitizer, high-speed printing can be performed without lowering water resistance and heat resistance. Suitable sensitivity is obtained. Further, dihydroxybenzophenone, 4,4'-dihydroxydiphenylsulfone and 2,2'-dimethyl-4,4,
By containing at least one of 4'-dihydroxydiphenylsulfone, the light fastness which could not be satisfied only by the combination of the above-described developer and sensitizer is improved, and the life of the coating solution is improved. Can also be improved. That is, by adding 0.1 to 5 parts, preferably 0.5 to 2.5 parts of any of these auxiliaries to 1 part of the developer, another auxiliary developer having strong light resistance is added. As a result, a material having excellent light fastness without causing background color development due to heat as in the case of (1) is obtained. Although the reason is not clear, the life of the coating liquid is improved, and a coating liquid which does not cause aggregation even after one month can be obtained. Next, other materials used in the present invention will be described.

The leuco dye used in the heat-sensitive recording layer of the present invention may be used alone or as a mixture of two or more kinds. As such a leuco dye, those applied to this kind of heat-sensitive material may be arbitrarily applied. For example, leuco compounds of dyes such as triphenylmethane type, fluoran type, phenothiazine type, auramine type, spiropyran type and indolinophthalide type are preferably used. Specific examples of such leuco dyes include, for example, 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-chlorofluoran, 3-dimethylamino-5,7 -Dimethylfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3-
Diethylamino-7,8-benzfluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-
(Np-tolyl-N-ethylamino) -6-methyl-
7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluoran, 2- {3 6-bis (diethylamino)-
Lactam 9- (o-chloroanilino) xanthylbenzoate, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-di- n-butylamino-7- (o-chloroanilino) fluoran, 3-N-methyl-N, n-amylamino-6-
Methyl-7-anilinofluoran, 3-N-methyl-N
-Cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3- (N, N-diethylamino) -5
-Methyl-7- (N, N-dibenzylamino) fluoran, benzoylleucomethylene blue, 6'-chloro-
8'-methoxy-benzoindolino-spiropyran, 6 '
-Bromo-3'-methoxy-benzoindolino-spiropyran, 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-4 ′)
-Dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3-
(N-ethyl-N-tetrahydrofurfuryl) amino-
6-methyl-7-anilinofluoran, 3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl-
7-anilinofluoran, 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluoran 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluoran, 3-pyrrolidino- 7-m-
Trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7-
(Di-p-chlorophenyl) methylaminofluoran, 3
-Diethylamino-5-chloro-7- (α-phenylethylamino) fluoran, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluoran, 3-diethylamino-7- (o- Methoxycarbonylphenylamino) fluoran, 3-diethylamino-
5-methyl-7- (α-phenylethylamino) fluoran, 3-diethylamino-7-piperidinofluoran, 2-chloro-3- (N-methyltoluidino) -7-
(Pn-butylanilino) fluoran, 3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluoran, 3-di-n-butylamino-6-methyl-7-anilino Fluorane, 3,6-bis (dimethylamino) fluorenespiro (9,3 ')-6'-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7- α-naphthylamino-4′-bromofluoran, 3-diethylamino-
6-chloro-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-4 ′, 5′-benzofluoran, 3-N-methyl-N-isopropyl-6
Methyl-7-anilinofluoran, 3-N-ethyl-N
-Isoamyl-6-methyl-7-anilinofluoran,
3-diethylamino-6-methyl-7- (2 ', 4'-dimethylanilino) fluoran and the like.

Next, the developer is not limited to the above-mentioned essential developer alone, and can be used in combination with another essential developer. Is possible. The sensitizer can be used in combination with the above-mentioned essential sensitizers alone or in combination with the following known sensitizers.

For example, fatty acid amides such as stearic acid amide, stearic acid ethylenebisamide, oleic acid amide, palmitic acid amide, palm fatty acid amide, behenic acid amide, zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, Waxes such as ester wax, dimethyl terephthalate, dibutyl terephthalate, dibenzyl terephthalate, dibutyl isophthalate, phenyl 1-hydroxynaphthoate, 1,2-di (3-methylphenoxy) ethane, , 2-Diphenoxyethane, 1-phenoxy-2
-(4-methylphenoxy) ethane, diphenyl carbonate,
p-benzylbiphenyl, 2,2′-methylenebis (4
-Methyl-6-t-butylphenol), 4,4'-butylidenebis (6-t-butyl-3-methylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-t-butyl) Phenyl) butane, 2,2′-methylenebis (4-ethyl-6-t-butylphenol),
2,4-di-t-butyl-3-methylphenol, 4,
Hindered phenols such as 4′-thiobis (3-methyl-6-t-butylphenol), 2- (2′-hydroxy-5′-methylphenyl) benzotriazole,
Sensitizers such as -hydroxy-4-benzyloxybenzophenone; and various heat-fusible substances such as lubricants, antioxidants, and UV inhibitors.

The auxiliaries used in the present invention include:
As described above, it is represented by the following structural formulas (1) to (3).

Embedded image Among them, those represented by the formula (1) have excellent effects.

In addition to the above essential components, various conventional binders can be used to bind these components on the support. Specific examples thereof include the following.
For example, polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate / Water-soluble polymers such as methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of isobutylene / maleic anhydride copolymer, polyacrylamide, sodium alginate, seratin, casein, etc. , Polyvinyl acetate, polyurethane,
Polyacrylate, polymethacrylate,
Emulsions such as vinyl chloride / vinyl acetate copolymers and ethylene / vinyl acetate copolymers, and latexes such as styrene / butadiene copolymers and styrene / butadiene / acrylic copolymers.

In the heat-sensitive coloring layer of the present invention, if necessary, auxiliary additives commonly used in this type of heat-sensitive recording material, such as fillers, surfactants, and heat-fusible substances, together with the above-mentioned components. (Or a lubricant), a pressure coloring portion stopper, and the like can be used in combination. Examples of the filler in this case include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, surface-treated inorganic fine powder such as calcium and silica, and the like. Organic fine powder such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin.

Examples of the lubricant include fatty acids such as stearic acid and behenic acid, metal salts of fatty acids such as aluminum stearate and zinc palmitate, and polymer waxes such as polyethylene wax and paraffin wax. In the present invention, when an overcoat layer (protective layer) is provided on the thermosensitive coloring layer, the same binder as that used for the thermosensitive coloring layer is used for the layer. If necessary, the above-mentioned fillers, auxiliary additives and the like can also be used. In the present invention, an undercoat layer may be provided between the support and the thermosensitive coloring layer as necessary, or for the purpose of improving image reliability between the thermosensitive coloring layer and the protective layer. Another protective layer may be provided. In this case, the filler, the binder, the heat-fusible substance, the surfactant and the like can be used as components constituting these layers.

[0016]

The present invention will be described in more detail with reference to the following examples. The parts and percentages shown below are based on weight.

Example 1 <Formation of thermosensitive coloring layer> [Solution A] 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluoran 20 parts Polyvinyl alcohol (10% aqueous solution) 20 Part Water 60 parts [Solution B] 4-hydroxy-4'-isopropoxydiphenyl sulfone 10 parts Calcium carbonate 10 parts Polyvinyl alcohol (10% aqueous solution) 20 parts Sensitizer (described in Tables 1 and 2) 5 parts Water 55 parts [Liquid C] Auxiliary developer (described in Tables 1 and 2) 20 parts Polyvinyl alcohol (10% aqueous solution) 20 parts Water 60 parts Each of the above [Liquid A], [Liquid B], and [Liquid C] The particles are dispersed in a sand mill so that the average particle diameter is 2 μm or less. Then, [Solution A], [Solution B] and [Solution C] were mixed and stirred at a weight ratio of 1: 6: 6 to form a thermosensitive coloring layer coating solution, and the dye adhesion amount was 0.5 g / m ² . It is coated on a high-quality paper of 50 g / m ² and dried to form a thermosensitive coloring layer.

<Formation of Overcoat Layer> [Solution D] 10 parts of calcined kaolin 10 parts of polyvinyl alcohol (10% aqueous solution) 10 parts of water 80 parts The above [Solution D] is dispersed by a sand mill and has an average particle size of 2 μm.
Adjust so that [Solution E] [Solution D] 40 parts Polyvinyl alcohol (10% aqueous solution) 40 parts Polyamide epichlorohydrin crosslinking agent (10% concentration) 12 parts Zinc stearate 2 parts Water 6 parts

A dry adhesion amount of 3 g / m on the thermosensitive coloring layer
[E solution] is applied and dried so as to be ² , thereby forming an overcoat layer. Then, it is passed twice through a super calender with a calender pressure of 30 kg. The samples shown in Tables 1 and 2 are prepared as described above. Example 6 shown in Tables 1 and 3 is a thermosensitive recording material produced in the same manner as in Example 1 except that the overcoat layer was not provided. Each sample was subjected to curing at 40 ° C. for 24 hours (the curing was not performed in Example 6), and the following evaluation was performed. Table 3 shows the results. <Evaluation items> After printing the "lightfast" sample on a heat block at 150 ° C,
Xenon light is irradiated for 16 hours with a fade meter, and the density of the image area is measured with a Macbeth reflection densitometer (RD-914). The “heat resistance” sample is placed in an environment of 70 ° C. for 1 hour, and the density of the background is measured with a Macbeth reflection densitometer (RD-914). "Dynamic Sensitivity" Using a thermal printing device equipped with a thermal head manufactured by Matsushita Electric Co., Ltd., printing was performed under the conditions of 24 V, 0.45 w / dot, pulse width of 0.1 to 1.2 μsec, and the print density was measured using a Macbeth reflection densitometer ( RD-914). The energy at which the concentration indicates 1.0 was calculated, and
The other examples are shown by energy magnification (sensitivity magnification). The larger the value, the better the “dynamic sensitivity”. After printing the "water resistant" sample with 150 inner blocks, 2
The sample was immersed in water at 0 ° C. for 16 hours, and the density of the image area was measured using a Macbeth reflection density (RD-914. “Liquidity”: “Solution A”, “Solution B”, “Solution C”: 6: 6: 1 and left in a constant temperature layer at 40 ° C. for 3 weeks to check whether aggregation has occurred.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3] (Note) Example 6 was produced in the same manner as in Example 1 except that the overcoat layer was not provided.

As is clear from Table 3, those of Examples are excellent not only in heat resistance and water resistance but also in light resistance, sensitivity and liquid property. In particular, Example 1 using dihydroxybenzophenone as an auxiliary obtained high values in all these properties (Example 6 without an overcoat layer was excluded from the comparison of water resistance). On the other hand, when the auxiliary agent is not used even when the developer and the sensitizer specified by the present invention are used, or when an auxiliary other than those specified in the present invention is used, particularly, the former case is used. Has poor light resistance and liquid property (see Comparative Example 1).
In the latter case, heat resistance and liquid properties are inferior (see Comparative Examples 4 to 6). Furthermore, when a developer other than the specified one was used, the light resistance and water resistance were inferior (see Comparative Example 3), and the sensitizer other than the specified one had low sensitivity (Comparative Example 7). Irradiation).

[0024]

As described above, according to the present invention, not only water resistance and heat resistance, but also particularly light resistance, and the aggregation of the coating solution for the color-forming layer hardly occurs, and it is suitable for high-speed printing. A heat-sensitive recording material having high sensitivity can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-69283 (JP, A) JP-A-4-310789 (JP, A) JP-A-63-246279 (JP, A) 24364 (JP, A) JP-A-5-262046 (JP, A) JP-A-5-24365 (JP, A) JP-A-4-357078 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5/34 CAPLUS (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A thermosensitive recording material having a thermosensitive coloring layer containing a leuco dye, a color developer and a sensitizer on a support, wherein 4-hydroxy-4'-isopropoxydiphenyl sulfone is used as a color developer. As a sensitizer, dioxalate (p-
Methylbenzyl), di (oxachlorate) (p-chlorobenzyl)
And at least one of dibenzyl oxalate and dihydroxybenzophenone, 4,4'-
A heat-sensitive recording material containing at least one of dihydroxydiphenylsulfone and 2,2'-dimethyl-4,4'dihydroxydiphenylsulfone.