JPH0710623B2 - Thermal recording paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention reduces the amount of debris adhering to the thermal head and improves the color developability thereof in thermal recording in a thermal facsimile, thermal printer or the like. For this purpose, a colorless or light-colored lactone compound and a thermosensitive paper consisting of a phenolic compound, which causes the color development of this chromogenic lactone compound when heated, have a mean pore size measured by a mercury press porosimeter between the support and the heat-sensitive layer of the support. Radius 0.2
The present invention relates to a thermal paper having an intermediate layer of micron or more in size.

(B) Conventional Technology and Problems Thermal paper is used to obtain an image record by utilizing physical and chemical changes of a substance due to thermal energy, and a great many processes have been studied. Of these, a two-component color-developing thermal paper is typical. The two-component color-developing thermal paper is a support in which two kinds of heat-reactive compounds are dispersed in the form of fine particles and a binder or the like is mixed to separate the two kinds of heat-reactive compounds from each other. It is applied on the recording medium, and recording is obtained by utilizing the coloring reaction that occurs when it is melted and contacted by heating.

Thermal paper, which uses a thermal head as a heat source and is composed of a normally colorless or light-colored lactone compound as a two-component color-forming compound and a phenol compound that develops the color of the lactone compound when heated, is becoming mainstream in recent facsimile communication.

In this thermal paper, the lactone dye and phenolic compound are basically melted by heating with a thermal head to develop color, and the melt adheres to the thermal head, damaging the head or degrading print quality. Was coming. Further, it is strongly desired to improve the color developability with the lowest possible energy in order to improve the communication speed, but generally, in order to prevent the dust adhesion, it is necessary to add a heat insoluble substance such as an oil absorbing pigment to the heat sensitive layer. However, there is a contradictory relationship with the improvement in color developability, and the balance cannot be said to be sufficient.

As a countermeasure, the inventors of the present invention have previously disclosed Japanese Patent Laid-Open No. 54-0222,
In JP-A-54-0227, JP-A-54-0704, etc., it has been proposed to provide an intermediate layer between the support and the heat-sensitive layer, but there have been cases where a sufficient effect cannot be obtained.

(C) Object of the Invention The purpose of the present invention is to prevent the adhesion of dust to the thermal head and improve the color developability by improving the intermediate layer provided between the support and the heat-sensitive layer in the two-component color heat-sensitive paper. It is intended to obtain a thermal paper which is compatible with each other, has excellent color developability, and has little dust adhesion.

(D) Means for Solving the Problems In the two-component color thermal paper, by providing an intermediate layer having an average pore radius of 0.2 micron or more measured by a mercury press porosimeter between the support and the thermal paper, It is intended to obtain a thermal paper having higher color development characteristics and less dust adhesion.

In addition, as the intermediate layer, JIS K-51 is used in terms of dust adhesion.
Inorganic powder with oil absorption by method 01 of 60 ml / 100 g or more is desirable, and further, calcined kaolin is optimal, and its effect is not sufficient if its coating amount is too small, and it rapidly increases at 4 g / m ² or more. The effect becomes remarkable.

In the present invention, the average porosity of the mercury porosimeter is measured based on the characteristics of the non-wetting liquid in the capillary, and the liquid having a wetting angle of 90 ° or more has pores by itself due to the surface tension. It is necessary to apply pressure from the outside in order to put the liquid into the pores without entering the inside, and the pore size is measured from the outside pressure. Specifically, MERCURY PRESSURE POROSIMETER MDD of Carlo Erba (Italy) Measured at 220.

The thermal paper of the present invention comprises a coater head such as an air knife, a blade or a roll on a support so that a white or light color pigment is coated on the first layer close to the support and a thermosensitive coloring layer is coated on the second layer. It is obtained by using the coating device that has.

Paper is generally used as the support, but synthetic paper, plastic film, non-woven fabric, or the like can be used if necessary.

The oil absorption of the intermediate layer is JISK
In the measuring method specified in -5101, 60 ml / 100 g or more is preferable, but 60 ml / 100 g or less pigment may be used in combination. From the viewpoint of smoothness, the particle size of the pigment is preferably 5.0 μm or less in terms of volume average particle size. Specifically, it is selected from kaolin, calcined kaolin, talc, wax, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium carbonate, titanium oxide, barium carbonate, urea-formalin filler and the like. When applied to a support, these pigments are dispersed together with a dispersant to form a starch derivative, polyvinyl alcohol, a water-soluble polymer adhesive such as styrene-maleic anhydride, a styrene-butadiene latex, or a hydrophobic polymer such as an acrylic resin emulsion. It is common to add the emulsion.

The thermosensitive coloring layer provided on the intermediate layer is mainly composed of a color former and a developer, but waxes, sensitivity improvers, metallic soaps, ultraviolet absorbers, etc. are added as necessary,
Further, the oil absorbing pigment may be mixed.

The color former used in the present invention is not particularly limited as long as it can be used for general pressure-sensitive recording paper, heat-sensitive recording paper and the like. Specific examples include (1) triarylmethane compound 3 , 3-Bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (Crystal
Violet lactone) 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethyl) Aminophenyl)-
3- (2-methylindol-3-yl) phthalide, 3
-(P-Dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis- (1,2
-Dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis- (1,2-dimethylindole-
3-yl) -6-dimethylaminophthalide, 3,3-bis- (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis- (2-phenylindole-3-) Yl) -5-dimethylaminophthalide, 3-
p-Dimethylaminophenyl-3- (1-methylhyrol-2-yl) -6-dimethyl-aminophthalide etc .:
(2) 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N as diphenylmethane compound
-Halophenyl leuco auramine, N-2,4,5-trichlorophenyl leuco auramine and the like: (3) Rhodamine B-anilinolactam, rhodamine B-p-nitroanilinolactam, rhodamine B as a xanthene compound
-P-chloroanilinolactam, 3-diethylamino-
7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-phenylfluorane, 3-diethylamino-7-
3,4-dichloroanilinofluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3
-Piperidino-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl-7-phenylfluorane, 3- Diethylamino-
7- (4-nitroanilino) fluorane, etc .: (4) As a thiazine-based compound, benzoylleuco methylene blue, p-nitrobenzoylleucomethylene blue, etc .:
(5) As the spiro compound, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran,
3,3'-dichloro-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methylnaphtho- (3
-Methoxy-benzo) -spiropyran, 3-propyl-
Mention may be made of spiro-dibenzopyran and the like, or mixtures thereof. These are determined by the application and the desired properties.

As the developer used in the present invention, a phenol derivative and an aromatic carboxylic acid derivative are preferable, and bisphenols are particularly preferable. Specifically, as phenols, p-octylphenol, p-tert-butylphenol, p-phenylphenol, 1,1-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) propane, 1,1-bis (p-hydroxyphenyl) pentane, 1,1-bis (p-hydroxyphenyl) hexane, 2,2-bis (p-hydroxyphenyl)
Hexane, 1,1-bis (p-hydroxyphenyl) -2
-Ethyl-hexane, 2,2-bis (4-hydroxy-3,5
-Dichlorophenyl) propane and the like.

As the aromatic carboxylic acid derivative, p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid,
In the case of 3,5-di-α-methylbenzyl salicylic acid and carboxylic acid, these polyvalent metal salts and the like can be mentioned.

Examples of the waxes include paraffin wax, kauna wax, microcrystalline wax, polyethylene wax, and higher fatty acid amides such as stearic acid amide, ethylene bisstearamide, and higher fatty acid ester.

Examples of the metal soap include higher fatty acid polyvalent metal salts, that is, zinc stearate, aluminum stearate, calcium stearate, zinc oleate and the like.

As the sensitivity improver, one having a sharp melting point of 80 to 140 ° C. and having good thermal response, specifically,
Benzoic acid or terephthalic acid esters, naphthalene sulfonic acid esters, naphthyl ether derivatives, anthryl ether derivatives, aliphatic ether-based sensitizers such as phenanthrene and fluorene can be used. Also, the above waxes can be used as a sensitizer.

These are dispersed and applied in a binder. Water-soluble binders are generally used, and polyvinyl alcohol, hydroxyethyl cellulose, hydroxypropyl cellulose, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer. Examples thereof include polymers, polyacrylic acid, starch derivatives, casein and gelatin. Also,
For the purpose of imparting water resistance to these binders, it is necessary to add a water resistance agent (gelling agent, cross-linking agent) or an emulsion of a hydrophobic polymer, specifically, styrene-butadiene rubber latex, acrylic resin emulsion, etc. You can also

(E) Action In the case where there is no intermediate layer in the two-component color thermosensitive paper or in the case of the mere oil absorbing pigment intermediate layer, when the heat sensitive layer is melted by printing with a thermal head or the like, the melted material is sufficiently applied to the base paper or intermediate layer Adhesion to the thermal head without absorption to the residue, resulting in dregs adhesion, but by providing an intermediate layer having an average pore radius measured by a mercury porosimeter of the present invention of 0.2 micron or more, the melt is Improving the ability to absorb instantly,
There is no adhesion to the thermal head side.

In addition, since the amount of dust can be reduced, the heat-insoluble matter in the heat-sensitive layer can be reduced, and the color developability can be improved.

Further, as compared with the case where no intermediate layer is provided, the heat-sensitive layer has a more uniform thickness due to the improvement in smoothness, and the printability is improved.

Further, the intermediate layer of the present invention, by increasing the average pore diameter in the coating layer to 0.2 micron or more as compared with the normal intermediate layer, when printing with a thermal head, acts as a heat insulating layer, less heat dissipation to the support side, It is considered that the printability of the heat-sensitive layer is improved.

(F) Examples Examples of the present invention will be shown below, but the present invention is not limited thereto. In addition, the part in an Example shows a weight part.

Example-1 Calcined kaolin (ANSILEX manufactured by Engelhard) Oil absorption 70 ml /
100 100 parts Sodium hexametaphosphate 0.8 parts 48% Styrene-butadiene latex (JSR0
692) 20 parts 130 parts of water was dispersed by stirring with a homogenizer (manufactured by Nippon Seiki) at 8000 rpm for 5 minutes, and then 20% phosphoric esterified starch (manufactured by Nippon Food,
MS-4600) was added to 25 parts, mixed well, and smeared on a high-quality paper of 40 g / m ^{2 so} that the smear amount was 6 g / m ² to obtain an undercoat paper.

On the other hand, as a heat-sensitive coating liquid, liquid A 3-diethylamino-6-methyl-7-anilinofluorane 1 part 5% hydroxyethyl cellulose 5 parts B liquid 4,4′-isopropylidenediphenol 1 part 5% hydroxyethyl cellulose 5 parts C Liquid 2-benzyloxynaphthalene 1 part 5% Hydroxyethylcellulose 5 parts Liquid A, B and C are separately dispersed for 4 hours with a paint conditioner (Igarashi Kikai), and the weight is A: B: C = 1: 5: 3. Mix at a ratio to make a heat-sensitive coating liquid, and apply this heat-sensitive coating liquid to the above-mentioned undercoat paper with a Meyer bar at an absolute dry coating amount of 5 g / m ²
And then dried at 60 ° C., and further smoothed with Beck smoothing for 200 to 300 seconds.

This thermal paper was recorded with a thin film thermal head manufactured by Matsushita Electronics Co., Ltd. (head voltage: 16 V, energization width: 1 msec), the density was measured with a Macbeth densitometer, and the amount of residue attached to the thermal head is shown in Table-1. .

At this time, the average pore diameter of the intermediate layer measured by the mercury porosimeter was 0.3 micron.

Example-2 Part of the calcined kaolin in Example-1 was replaced with light carbon calf (Shiraishi Kogyo Callite SA, oil absorption 95 ml / 100 g),
The results obtained in the same manner are shown in Table-1.

Example-3 In place of calcined kaolin in Example-1, silicic acid (Mizukasil P-832 manufactured by Mizusawa Chemical Co., Ltd., oil absorption 132 ml / 100 g) was substituted, and the same results are shown in Table-1.

Comparative Example-1 Dispersion of calcined kaolin at 56% by weight in Example-1 was carried out for 1 hour by a tabletop sand mill (made by Campe Household Coating Co., Ltd.), and the solution was adjusted to have the same ratio. The average porosity measured by the formula porosimeter was 0.16 micron (this is considered to be due to the fact that calcined kaolin causes shearing more than necessary and causes a structural change, resulting in a decrease in the porosity of the coating layer.

Comparative Example 2 Table 1 shows the results obtained in the same manner as in Example 1 except that the calcined kaolin was replaced with kaolin (Engelhard, Ultra White 90, oil absorption 39 ml / 100 g).

Comparative Example-3 Table 1 shows the results obtained in the same manner as in Example-1, except that calcined kaolin was replaced with heavy calcium carbonate (Softon 2200, manufactured by Shiraishi Industry Co., Ltd., oil absorption 44 ml / 100 g).

Comparative Example-4 Table-1 shows the results obtained in the same manner as in Example-1, except that the amount of undercoat paper smeared was 3 g / m ² .

(G) Effect of the Invention As is clear from the examples, by providing an intermediate layer having an average pore radius of 0.2 micron or more in the mercury porosimetry porosimeter of the present invention, the color density is high and the dust adhesion property is high. The result is a non-thermal paper.

Continuation of the front page Judgment panel Judgment Chief Judge Norihide Funada Judge Yuichi Ikeda Judge Takehiko Takahashi (56) References JP 59-155097 (JP, A) JP 56-86792 (JP, A)

Claims (4)

[Claims] 1. An average pore radius measured by a mercury penetration type porosimeter between a support and a heat-sensitive layer basically containing a colorless or light-colored lactone compound and a phenol compound is 0.
Thermal recording paper characterized by having an intermediate layer of 2 microns or more. 2. The oil absorption of the intermediate layer according to JIS K-5101 method is 60 ml.
The thermosensitive recording paper according to claim 1, which is an inorganic powder of 100 g or more. 3. The heat-sensitive recording paper according to claim 2, wherein the intermediate layer is calcined kaolin. 4. The heat-sensitive recording paper according to claim 1, 2 or 3, wherein the coating amount of the intermediate layer is 4 g / m ² or more.