JPH05238143A - Thermosensitive recording material - Google Patents

Abstract

(57) [Abstract] [Purpose] To further improve the sensitivity of a thermal recording material having an undercoat layer using a hollow filler and to improve the stability of the coating solution for the undercoat layer. In a thermosensitive recording material having an undercoat layer containing a plastic spherical hollow filler and a thermosensitive coloring layer containing a leuco dye and a color developer as main components on a support,
The hollow filler has a particle size of 1 μm or less and a hollow ratio of 80.
% Or less and a filler having a particle diameter of 3 to 10 μm and a hollow ratio of 80% or more are mixed and used.

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, and more specifically, by providing an undercoat layer between a support and a heat-sensitive color-developing layer, the sensitivity is improved and the liquidity and coating property of the coating solution for undercoat layer are improved. It also relates to improvement of workability.

[0002]

2. Description of the Related Art Recently, various recording materials have been researched and developed and put to practical use in the information recording field in response to social demands such as diversification and increase of information, resource saving, and pollution-free. Among them, the heat-sensitive recording material is (1) a color-developed image is recorded by simply heating and a complicated developing step is unnecessary.
(2) It can be manufactured using a relatively simple and compact device, and the obtained recording material is easy to handle and inexpensive to maintain. (3) Paper is often used as a support. In that case, not only the support cost is low, but also the feel of the obtained recorded matter is close to plain paper, so that the output of computers, the field of printers such as calculators, the field of recorders for medical measurement, It is widely used in the fields of low-speed and high-speed facsimiles, automatic ticket vending machines, and thermal copying.

The above-mentioned thermosensitive recording material is usually prepared by coating and drying a thermosensitive coloring layer coating solution containing a coloring component capable of causing a coloring reaction by heating on a support such as paper, synthetic paper or synthetic resin film. The heat-sensitive recording material thus obtained is heated with a hot pen or a thermal head to record a color image.

As a conventional example of such a thermal recording material, for example, a thermal recording material disclosed in JP-B-43-4160 or JP-B-45-14039 can be mentioned. For example, the thermal response was low, and sufficient color density was not obtained during high speed recording.

As a method for improving such a defect, as a leuco dye, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane (see JP-A-49-109120) and 3- Development of high-sensitivity dyes such as dibutylamino-6-methyl-7-anilinofluorane (see JP-A-59-190891), and further development of 1,7-bis (4- Hydroxyphenylthio) -3,5-dioxaheptane
(See JP-A-59-106456), 1,5-bis (4-hydroxyphenylthio) -3-oxapentane (JP-A-59-116262)
It has been proposed to increase the speed and increase the sensitivity by using the method described in Japanese Patent Publication (KOKAI). Further, in JP-A-61-123584, JP-A-61-215087, JP-A-61-242889 and the like, attempts have been made to increase the speed and sensitivity by combining the substances mentioned above.

On the other hand, as a technique for improving the heat insulating property of the undercoat layer and increasing the sensitivity, one using fine hollow particles (see JP-A-59-5093) and two kinds of fillers having different expansion ratios by heating. Using (Japanese Patent Laid-Open No. 1-9768
No. 0), etc.

However, such hollow fillers having a large particle size of 3 to 10 μm and a high hollow ratio of 80% or more contain a large amount of air, and therefore, when contained in the coating solution of the undercoat layer, the coating layer There is a drawback that the coating of the item floats and it is difficult to apply. Moreover, the particle size is 1 μm or less,
Thermal recording materials using hollow fillers having a hollow ratio of 80% or less had sufficiently high sensitivity in the past, but recently, more sensitive thermal recording materials have been demanded.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat sensitive recording material which has improved the above-mentioned conventional drawbacks.
That is, it is to provide a thermosensitive recording material having high sensitivity and improved stability of the coating liquid for undercoat layer.

[0009]

The present invention provides a thermosensitive recording material comprising a support and an undercoat layer containing a plastic spherical hollow filler and a thermosensitive coloring layer containing a leuco dye and a color developer as a main component. A heat-sensitive recording material comprising a filler A having a particle size of 1 μm or less and a hollow ratio of 80% or less and a filler B having a particle size of 3 to 10 μm and a hollow ratio of 80% or more as a hollow filler. ..

Fillers for the undercoat layer generally used in heat-sensitive recording materials include calcium carbonate, silica, kaolin,
Inexpensive and inorganic pigments such as talc, clay and calcined kaolin are used. These fill the irregularities of the base paper and improve the smoothness of the thermal paper, thus contributing to the improvement of the sensitivity to a certain extent, but the thermal insulation is insufficient, and a large improvement in the sensitivity cannot be expected.

On the other hand, the hollow filler having good heat insulation has a particle size of 1
Hollow fillers with a hollowness of 80 μm or less and μm or less are generally used, but in order to further improve the heat insulating property, use a hollow filler with a larger particle size of 3 to 10 μm and a hollowness of 80% or more. Has been desired theoretically. However, when such a hollow filler having a large particle diameter and a high hollow ratio is put in the coating liquid for the undercoat layer, it floats in the liquid and does not adapt to the liquid, so that there is a drawback that it cannot be mass-produced actually. ..

However, the particle size is 1 μm or less and the hollow ratio is 8
Hollow filler of 0% or less and particle size of 3 to 10 μm, hollow rate of 80
% Or more of the hollow fillers mixed in a ratio of 9: 1 to 1: 9, the heat insulation of the undercoat layer is good,
It was found that a heat-sensitive recording material having a good compatibility with hollow particles can be provided as a coating liquid for the undercoat layer.

The hollow ratio mentioned here is the ratio of the outer diameter to the inner diameter of the hollow particles, and is represented by the following formula.

[Equation 1]

Examples of the plastic spherical hollow particles used in the present invention include polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylic acid ester, polyacrylonitrile, polybutadiene, and copolymers thereof. The gas contained in the shell is generally propane, butane, air or the like.

To form the undercoat layer on the support, the plastic spherical hollow particles are dispersed in water together with a binder such as a well-known water-soluble polymer or aqueous polymer emulsion, and this is coated on the surface of the support. And dried. In this case, the coating amount of the spherical plastic hollow particles is at least 1 g, preferably about ^{2 to} 15 g per 1 m ² of the support, and the coating amount of the binder resin is such that the undercoat layer is strongly bonded to the support. Well, it is usually 2 to 50% by weight based on the total amount of the plastic spherical hollow particles and the binder resin.

Specific examples of the hollow filler having a particle size of 1 μm or less and a hollow ratio of 80% or less include OP-62 HV-91 manufactured by Rohm & Haas Co., Ltd. Mitsui 1103E manufactured by Mitsui Toatsu Chemicals, Inc. particle size of 3-10 μm Specific examples of the hollow filler having a hollow ratio of 80% or more include Hollow Filler R-3 manufactured by Matsumoto Yushi-Seiyaku Co., Ltd., but are not limited thereto.

In the present invention, the binder used when forming the undercoat layer is appropriately selected from conventionally known water-soluble polymers and / or aqueous polymer emulsions. Specific examples thereof include water-soluble polymers such as polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as methoxycellulose, hydroxyethylcellose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / Acrylic ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, styrene /
Examples thereof include maleic anhydride copolymer alkali salts, isobutylene / maleic anhydride copolymer alcal salts, polyacrylamide, sodium alginate, gelatin, and casein. Examples of the aqueous polymer emulsion include latex of styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, vinyl acetate resin, vinyl acetate / acrylic acid copolymer, styrene / acrylic acid ester copolymer, Examples thereof include emulsions of acrylic acid ester resins and polyurethane resins.

In the undercoat layer of the present invention, together with the plastic spherical hollow particles and the binder, if necessary, further auxiliary additives commonly used in this type of heat-sensitive recording material, for example, fillers and heat-fusible substances are used. ,
A surfactant or the like can be used in combination. In this case, as specific examples of the filler and the heat-fusible substance, various ones described in connection with the thermosensitive coloring layer component in the following will be mentioned.

Since the surface of the undercoat layer formed on the support as described above has considerable unevenness, a flat surface may be smoothed by calendering after the undercoat layer is formed.

The leuco dyes used in the color forming layer in the present invention may be used alone or in admixture of two or more, and as such leuco dyes, those applied to this type of heat-sensitive recording material are arbitrary. Leuco compounds of dyes such as triphenylmethane type, fluorane type, phenothiazine type, auramine type, spiropyran type and indolinophtalide type dyes are preferably used. Specific examples of such leuco dyes include those shown below. 3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactan), 3,3-bis (p- Dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p
-Dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-
Dimethylfluorane, 3- (N, N-diethylamino) -5-methyl-7- (N, N-dibenzylamino) fluorane, benzoylleuco methylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrrirospirane , 6'-bromo-3'-methoxy-
Benzoindolino-pyrrilospirane, 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'-dimethyl Aminophenyl) -3- (2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3-morpholino-7- (N-propyl-trifluoromethylanilino) furiolane, 3-pyrrolidino-7-
Trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane , 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3- (Np-tolyl-N-
Ethylamino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-
Trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6-bis (diethylamino) -9- (o
-Chloranilino) xanthyl benzoate lactam}, 3-
Diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-N-methyl -N-amylamino-6-
Methyl-7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-pyrrolidino- 7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino)-
7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino)
Fluorane, 3-diethylamino-5-methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-
Piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7- (pn-butylanilino) fluorane, 3- (N-
Methyl-N-isopropylamino) -6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorene spiro (9,3 ') -6-Dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-
Chlor-7-anilinofluorane, 3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6 -Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4 ', 5'-benzofluorane and the like. 3-N-methyl-N-isobutyl-6-methyl-7-anilinofluorane, 3-N
-Ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-N-diethylamino-6-methyl-7- (2 ', 4'-dimethylanilino) fluorane,

In the present invention, various electron-accepting compounds, such as phenolic compounds, are used as color developers.
A thiophenolic compound, a thiourea derivative, an organic acid and a metal salt thereof can be used in combination as necessary, and specific examples thereof will be shown below. 4,4'-isopropylidene bisphenol, 4,4'-isopropylidene bis (o-methylphenol), 4,4'-secondary butylidene bisphenol,
4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-cyclohexylidene diphenol, 4,
4'-isopropylidene bis (2-chlorophenol), 2,2 '
-Methylenebis (4-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-2-methyl) phenol , 1,1,3-tris (2-methyl-
4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-
Tris (2-methyl-4-hydroxy-5-tert-cyclohexylphenyl) butane, 4,4'-thiobis (6-tert-butyl-2)
-Methyl) phenol, 4,4'-diphenolsulfone, 4-
Isopropoxy-4'-hydroxydiphenyl sulfone, 4-
Benzyloxy-4'-hydroxydiphenyl sulfone, 4,4 '
-Diphenol sulfoxide, isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, benzyl protocatechuate, 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- Metal salts of 2-naphthoic acid, hydroxynaphthoic acid such as zinc, aluminum and calcium. Bis (4-hydroxyphenyl) acetic acid methyl ester, bis (4-hydroxyphenyl) acetic acid benzyl ester, 1,3-bis (4-hydroxycumyl) benzene, 1,4-bis (4-hydroxycumyl) benzene, 2,4'-diphenol sulfone, 3,3'-diallyl-4,4'-diphenol sulfone, 2,2-bis (4-hydroxyphenyl) -α-methyltoluene, zinc thiocyanate antipyrine complex, tetra Bromobisphenol A, tetrabromobisphenol S, 3,4-dihydroxy-4'-methyl-diphenyl sulfone,

Further, in order to improve its thermal response, a heat-fusible substance may be contained in the heat-sensitive color forming layer. Examples of preferable heat-fusible substances include benzyl p-benzyloxybenzoate, β-naphthyl-benzyl ether, stearamide, stearyl urea, p-benzylbiphenyl, di (2-methylphenoxy) ethane, di (2 -Methoxyphenoxy) ethane, β-naphthol- (p-methylbenzyl) ether, α-naphthylbenzyl ether, 1,4-butanediol-p-methylphenyl ether, 1,4-butanediol-p-isopropylphenylether, 1,4-butanediol-p-tert-octylphenyl ether, 1-phenoxy-2- (4-ethylphenoxy) ethane, 1-phenoxy-2- (4-chlorophenoxy) ethane, 1,4-butanediolphenyl Ether, diethylene glycol bis (4-
Methoxyphenyl) ether and the like can be mentioned. The heat-fusible substance may be used alone or as a mixture, and in order to obtain a sufficient thermal response, 10 to 30 with respect to the electron-accepting compound.
It is preferable to use 0% by weight, more preferably 20%
~ 200% by weight.

As the binder used in the color forming layer, for example, polyvinyl alcohol, starch and its derivatives,
Cellulose derivatives such as methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid ternary copolymer Polymer, styrene / maleic anhydride copolymer alcar salt, isobutylene / maleic anhydride copolymer alkali salt, water-soluble polymer such as polyacrylamide, sodium alginate, gelatin, casein, polyvinyl acetate, polyurethane, styrene / Butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, styrene / butadiene / Or a latex such as acrylic copolymer.

As the filler, auxiliary additives commonly used in this type of heat-sensitive recording material, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, In addition to surface-treated inorganic fine powders such as calcium and silica, urea-
Examples thereof include organic fine powders such as formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin.

In addition, sensitizers, lubricant waxes, surfactants, auxiliaries and the like which are generally used in the heat-sensitive color forming layer can be used if necessary.

In the heat-sensitive recording material of the present invention, for example, a color-forming undercoat layer and a coating solution for forming a heat-sensitive color-forming layer containing the above-mentioned respective components are sequentially applied and dried on a support such as paper, synthetic paper and plastic film. And calendered. In this case, it is possible to provide an overcoat layer on the color forming layer. Leuco dye, developer,
The amounts of other auxiliary additives used are appropriately 5 to 40% by weight and 20 to 60% by weight, respectively.

[0027]

EXAMPLES Next, the present invention will be described in more detail by way of examples. The parts and% shown below are based on weight.

Example 1 [Liquid A] 20 parts of 3- (N-methyl-3-N-cyclohexyl) amino 6-methyl-7-anilinofluorane 20 parts of 10% polyvinyl alcohol aqueous solution 60 parts of water [Solution B] 1,5-bis (4-hydroxyphenylthio) -6-methyl-7 10 parts-anilinofluorane-calcium carbonate 15 parts-polyvinyl alcohol 10% aqueous solution 25 parts-water 50 parts The average particle size of each of the mixtures is 2.5
Disperse using a sand mill so that the particle size becomes less than μm.
Solution] and [B Solution] were prepared.

[Liquid C] 15 parts of plastic spherical hollow particle dispersion (filler B) (solids concentration 32%, average particle size 5 μm, hollow ratio 92%) 15 parts plastic spherical hollow particle dispersion (filler A) (Rohm and Haas Company OP-62, solid content concentration 37.5%, average particle size 0.4 μm, hollow ratio 65%) ・ Styrene-butadiene copolymer latex (solid content concentration 47.5%) 10 parts ・ water 60 parts An undercoat layer coating solution is prepared by stirring and dispersing a mixture consisting of, and this is applied to a commercially available high-quality paper (basis weight 52 g / m ² ).
An undercoat paper was obtained by coating and drying the surface of the above so that the weight after drying was 5 g / m ² .

Next, [solution A] and [solution B] were mixed and stirred in a weight ratio of 1:10 to prepare a thermosensitive color forming layer-forming solution, which was dried on the surface of the undercoat paper. After coating and drying so as to have a weight of 5 g / m ² , a thermosensitive coloring layer was provided, and then supercalendering was performed so that the Beck smoothness was 600 to 700 seconds to obtain a thermosensitive recording material of the present invention. ..

Example 2 Another plastic spherical hollow particle dispersion (filler B) in the liquid C of Example 1 was another plastic spherical hollow particle dispersion (solid content concentration 30%, average particle diameter 10 μm, hollow ratio 93).
%) Was used to obtain a thermosensitive recording material in the same manner as in Example 1.

Example 3 Another plastic spherical hollow particle dispersion (solids concentration 30%, average particle diameter 9 μm, hollow ratio 93) as the plastic spherical hollow particle dispersion (filler B) in the liquid C of Example 1 was used.
%) Was used to obtain a thermosensitive recording material in the same manner as in Example 1.

Example 4 Another plastic spherical hollow particle dispersion (filler B) in the liquid C of Example 1 was another plastic spherical hollow particle dispersion (solid content concentration 30%, average particle diameter 3 μm, hollow ratio 96).
%) Was used to obtain a heat-sensitive recording material in the same manner.

Example 5 Another plastic spherical hollow particle dispersion (filler B) in the liquid C of Example 1 was another plastic spherical hollow particle dispersion (solid content concentration 32%, average particle diameter 7 μm, hollow ratio 89).
%) Was used to obtain a thermosensitive recording material in the same manner as in Example 1.

Comparative Example 1 In Example 1, only filler A was used without using filler B.
A thermal recording material for comparison was obtained in the same manner as in Example 1 except that 30 parts were used.

Comparative Example 2 A thermal recording material for comparison was obtained in the same manner as in Example 1 except that the plastic spherical hollow fine particles A were not used and only 30 parts of the filler plastic spherical non-hollow particles B were used.

The thermal recording material thus obtained was tested for kinematic sensitivity and dot reproducibility. The results are shown in Table 1. The test method was as follows.

Dynamic color development: In a thermal printing experimental device having a thin film head manufactured by Matsushita Electronic Parts Co., head power 0.45 W / dot, 1 line recording time 20 ms / l, scanning line density 8 × 3.85 dots / mm Was printed with a pulse width of 0.3, 0.4, 0.5, and 0.6 msec, and the print density was measured with a Macbeth densitometer RD-914. Dot reproducibility: The image obtained by the test method was visually evaluated. 5 Rank evaluation 5 Very good 2 Poor 4 Good 1 Very bad 3 Normal Head matching property: It was evaluated based on the amount of residue attached to the head during the test. 5 rank evaluation Liquidity: Separation of liquid (whether the filler floats) was evaluated 1 hour after the undercoat liquid was prepared. 5 rank evaluation

[0039]

[Table 1] Table 1

From the results shown in Table 1, the thermal recording materials of Examples were
It can be seen that the sensitivity is high and the dot reproducibility, head matching property, and liquid property are excellent.

[0041]

As described above, according to the heat-sensitive recording material of the present invention, it is possible to obtain a heat-sensitive recording material having a very high sensitivity and an improved liquidity when the undercoat layer is applied.

Claims (2)

[Claims] 1. A thermosensitive recording material comprising a support and an undercoat layer containing a plastic spherical hollow filler and a thermosensitive coloring layer containing a leuco dye and a color developing agent as a main component, wherein the hollow filler has a particle size of 1 μm. Filler A having a hollow ratio of 80% or less, a particle size of 3 to 10 μm, and a hollow ratio of 8
A heat-sensitive recording material comprising a mixture of 0% or more of filler B. 2. The filler B has a particle size of 3 to 10 μm,
The heat-sensitive recording material according to claim 1, wherein a filler having a hollow ratio of 90% or more is used.