JP2871165B2 - Manufacturing method of 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. More specifically, the present invention relates to a method for producing a thermosensitive recording material having a uniform and stable coating layer structure.

[0002]

2. Description of the Related Art A thermosensitive recording system is highly evaluated for its advantages such as the ability to obtain a color image simply by heating, and that the recording apparatus can be made relatively simple and compact. Widely used.

In particular, in recent years, facsimile printers using such a thermal recording system have been improved, and high-speed, high-quality recording, which has been conventionally difficult, has become possible. As the speed and the image quality of such devices have been increased, the thermal recording materials used therein have been required to further improve the recording sensitivity and to make the coating layer uniform, and many proposals have been made regarding this. Such a heat-sensitive recording material in which a heat-sensitive recording layer mainly composed of a binder and a thermochromic substance is formed as a single layer or a multi-layer on a support made of paper, plastic film, synthetic paper, or the like. Is commonly used.

In order to improve the recording sensitivity and image quality of the heat-sensitive recording material having such a structure, it is necessary to increase the adhesion between the thermal head and the surface of the heat-sensitive recording material. Therefore, as a means for improving this, a process for improving the smoothness of the recording layer surface using a super calender, a gloss calender, or the like has been extremely commonly performed in the production of recording materials, and Japanese Patent Publication No. 52-20142 discloses recording. It has also been proposed that the Beck smoothness of the layer surface be 200 to 1000 seconds. However, due to recent improvements in the thermal head, each dot constituting the thermal head has conventionally progressed from about 200 μm on one side to 50 μm or less, and the smoothness of the recording layer surface is simply reduced by supercalendering or the like. Satisfactory image quality reproducibility has not always been obtained even with a struggle.

Therefore, there has been proposed an attempt not to forcibly form a uniform heat-sensitive recording material surface by a super calendar or the like but to form a uniform layer during coating (Japanese Patent Publication No. 62-16196, Japanese Patent Publication No. Sho 62-16196, Kaisho 64-565
No. 84, JP-A-61-274986). However, this is intended to be achieved by a coating method, but the coating properties vary depending on the fluidity of the paint, and as a result, a uniform layer structure is not always formed, and this is not a sufficient technique.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a heat-sensitive recording material which can solve the above-mentioned drawbacks of the prior art, can form images with good uniformity, and is suitable for high-speed manufacturing.

[0007]

According to the present invention, a Hercules viscometer of 8800 rpm is used for a thermosensitive recording material provided with a thermosensitive coloring layer utilizing a thermosensitive coloring reaction between a dye precursor and a developer on at least one surface of a support. At 20c
ps or more (high shear viscosity) and 6
After applying an undercoat layer paint having a viscosity at 0 rpm of 400 cps or more (low shear viscosity) from a jet fountain to a base material, high-speed production is possible by controlling the amount of coating with a blade and applying the undercoat layer. It has been found that coating uniformity can be improved, and that a thermosensitive recording material provided with a thermosensitive coloring layer thereon can obtain good quality of image uniformity, and have completed the present invention.

It has been conventionally known that in a thermosensitive recording material having a structure of a thermosensitive coloring layer, an undercoat layer and a support, it is important that the coating uniformity of the undercoat layer is important for image uniformity. It has been proposed to improve the smoothness by calendering (Japanese Patent Application Laid-Open No. 56-879921). However, since the heat insulating property, which is an important physical property of the undercoat layer, is impaired by the super calender, the image uniformity is improved, but the sensitivity is improved. Causes a drop in

As a coating method, an air knife, a bar, a blade, and the like are generally known, but a uniform layer structure capable of providing high-quality printing required for recent heat-sensitive recording materials is obtained. For this reason, in the case of air knife or bar coating, the coating solution concentration is low, so that the coating material is largely penetrated into the base material and a uniform layer structure cannot be formed. On the other hand, since blade coating can be applied at a high concentration and has a low permeation into the base material and can form a uniform layer, it is becoming popular as a coating method for thermosensitive recording materials.

[0010] The blade system, which is a coating system capable of forming a coating layer with high uniformity, requires a coating liquid to be uniformly applied to the substrate in order to exhibit its performance.

There are four coating methods: jet fountain, die fountain, roll application, and chamber application. The jet fountain method is most suitable as a method capable of uniform coating at high speed. Therefore, as a result of earnestly studying coating properties suitable for high-speed coating by a method of controlling the coating amount with a blade after coating on a base material with a jet fountain, a Hercules viscometer was used for high-speed coating (coating speed 400 m / min or more). BL at 8800 rpm is more than 20 cps
When a thermosensitive coloring layer coating material having a viscosity at 60 rpm of a viscometer of 400 cps or more was used, it was found that this coating method was most suitable.

When the viscosity at 8800 rpm of the Hercules viscometer is 20 cps or less, the coating amount is not obtained. When the viscosity at 60 rpm of the BL viscometer is 400 cps or less, the coating liquid cannot be uniformly supplied to the base material from the jet fountain. There is a problem that the coated surface is roughened.

[0013] Blade coating is roughly classified into three types: tip, vent, and rod. In any of these types, a uniform layer structure cannot be achieved unless the coating material properties within the scope of the present invention are satisfied.

The undercoat layer in the present invention comprises a filler and an adhesive. As the filler, inorganic and organic pigments used for general papermaking and coating are optionally used. Are included.

Calcium carbonate, kaolin, talc, zinc oxide, aluminum hydroxide, silica, magnesium silicate, polythrene resin, urea-formaldehyde resin and the like.
Generally known water-soluble emulsions and aqueous emulsions are used, and specific examples thereof include the following. Polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, starch, starch derivatives, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer,
SBR latex, polyvinyl acetate emulsion, etc.

The coating composition of the undercoat layer is arbitrarily mixed so as to have the coating properties of the present invention.
² , preferably 10 g / m ² or more.

The dye precursor contained in the heat-sensitive coloring layer of the present invention is not particularly limited as long as it is used for general pressure-sensitive recording paper, heat-sensitive recording paper and the like. Specific examples are as follows: (1) As a triarylmethane compound, for example, 3,
3-bis (P-dimethylaminophenyl) -6-dimethylaminophthalide and the like. (2) As the diphenylmethane compound, for example,
4'-bis-dimethylaminobenzhydrin benzyl ether, N-2,4,5-trichlorophenylleucouramine, N-2,4,5-trichlorophenylleucouramine and the like. (3) As a xanthene compound, for example, rhodamine B
-Anilinolactam, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-7-butylaminofluoran, 3-diethylamino-7- (2-
Chloroanilino) fluoran, 3-piperidino-6-methyl-7-anilinofluoran, 3-ethyl-tolylamino-6-methyl-7-anilinofluoran, 3-cyclohexyl-methylamino-6-methyl-7-ani Linofluoran, 3-diethylamino-6-chloro-7- (β
-Ethoxyethyl) aminofluorane, 3-diethylamino-6-chloro-7- (γ-chloropropyl) aminofluoran, 3-ethyl-isoamylamino-6-methyl-7-anilinofluoran, 3-dibutylamino -7
-Chloroanilinofluoran and the like. These are used alone or as a mixture of two or more. The dye precursor is appropriately selected and used depending on the use of the heat-sensitive recording material and desired properties.

As the color developer used in the present invention, phenol derivatives and aromatic carboxylic acid derivatives are preferable, and bisphenols are particularly preferable. This is specifically exemplified by phenols such as p-octylphenol and p-octylphenol.
-Tert-butylphenol, P-phenylphenol, 1,1-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) pentane, 1,1-bis (p-hydroxyphenyl) hexane, , 2-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) -2-ethyl-hexane, 2,2-bis (4-hydroxy-3,
5-dichlorophenyl) propane, dihydroxydiphenyl ether and the like.

The aromatic carboxylic acid derivatives include p
-Hydroxybenzoic acid, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid, 3,5
-Di-a-methylbenzylsalicylic acid, and polyvalent metal salts of the above carboxylic acids.

In the production of the heat-sensitive recording material of the present invention, various auxiliaries such as a surfactant and an antifoaming agent can be added as long as the effects of the present invention are not impaired. Examples of the wax contained in the heat-sensitive recording layer include paraffin wax, carnauba wax, microcrystalline wax, polyethylene wax, and higher fatty acid amides such as stearic acid amide, ethylenebisstearamide, and higher fatty acid esters.

Examples of the metal soap include higher fatty acid polyvalent metal salts, such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate.

Examples of the inorganic pigments include kaolin, calcined kaolin, talc, wax, diatomaceous earth, calcium carbonate, aluminum hydroxide, magnesium hydroxide, magnesia,
Examples include titanium oxide and barium carbonate. Examples of the sensitizer include p-benzylbiphenyl, dibenzyl terephthalate, phenyl 1-hydroxy-2-naphthoate, dibenzyl oxalate, di-o-chlorobenzyl adipate,
1,2-di (3-methylphenoxy) ethane, di-p-chlorobenzyl oxalate, bis (Pmethylbenzyl) oxalate and the like can be mentioned.

These are applied to a support together with a binder. As a binder, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose,
Can be combined with hydroxypropyl cellulose, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyacrylic acid, polyacrylic acid, starch, casein, gelatin, etc. it can. For the purpose of imparting water resistance to these binders, a water resistance imparting agent can be added, or a hydrophobic emulsion, specifically, a styrene-butadiene rubber lux, an acrylic resin emulsion, or the like can be added. The coating solution is applied to one surface of the sheet-like support at 3 to 8 g / m ^2.
(Dry), whereby a heat-sensitive recording layer is formed.

As a method of forming the heat-sensitive recording layer, an air knife method, a blade method, a gravure method, a roll coater method,
Any of the known methods such as spraying, dipping, bar and extrusion may be used,
Preferably, a coating method such as a blade method capable of forming a coating layer having a good surface property is preferable. The support material used in the present invention is not particularly limited, and for example, paper, synthetic paper, synthetic fiber paper, synthetic resin film, and the like can be appropriately used. When paper is used as the support, the pulp beating degree (CS
F) is desirably 400 ml or more.

[0025]

The present invention will be further described by way of examples. Example 1 As coating liquid for undercoat layer The above components were mixed to give a coating liquid for an undercoat layer. This coating solution was applied to a support from a jet fountain, and 600 m /
blade (blade angle 20 °, blade thickness 0.508 mm) so that the coating amount after drying at a coating speed of min is 10 g / m ^2.
After controlling the coating amount by drying, an undercoat layer was formed by drying.

On the other hand, dispersions A and B were used as coating liquids for the thermosensitive coloring layer.
Was prepared. Preparation of Dispersion A A vertical sand mill (manufactured by Imex Co., Ltd.)
Sand grinder), and subjected to a dispersion miniaturization operation using glass beads having a diameter of 1.2 mm as a dispersion medium for 30 minutes. Subsequently, the composition was sand-milled (Diafine mill, manufactured by Mitsubishi Heavy Industries, Ltd.). , And subjected to a dispersion miniaturization operation using glass beads having a diameter of 0.6 mm as a dispersion medium for 30 minutes.

Preparation of Dispersion B This composition was dispersed by the same method as that for preparing the dispersion A.

Preparation of Coating Solution for Thermosensitive Recording Layer To 50 parts of the dispersion A and 100 parts of the dispersion B, 30 parts of calcium carbonate, 30 parts of a 33% paraffin dispersion,
10% Polyvir alcohol (Nippon Synthetic Chemical Industry Co., Ltd.)
NM11) 100 parts of an aqueous solution were mixed and stirred to prepare a coating solution. This coating solution was applied and dried on the undercoat layer formed as described above so that the coating amount after drying was 4.5 g / m ² to form a thermosensitive coloring layer. Thermal recording paper was manufactured using a super calender at 800 seconds with an Oken type smoothness meter. Further, the recording sensitivity of the obtained thermosensitive recording paper and the uniformity of the image were evaluated. Recording sensitivity was measured using Oki Electric's high-speed facsimile: OF-6A using the standard chart No.2 of the Institute of Image Electronics Engineers of Japan, and the color density at that time was measured with a Macbeth densitometer RD-914 to represent the recording sensitivity of thermal recording paper. At the same time, the uniformity of the image was visually evaluated. The results are shown in Table 1.

[Table 1]

Example 2 A heat-sensitive recording paper was prepared by performing the same processing as in Example 1 except that the coating amount of the undercoat layer was changed from a blade to a rod blade (rod rotation speed: 600 rpm, rod diameter: 8 mm). .

Comparative Example 1 Acrylic emulsion blended in the undercoat layer in Example 1 (Nippon Acrylic Co., Ltd., trade name: Primal RM-5)
A heat-sensitive recording paper was prepared by performing the same processing as in Example 1 except for the following. Comparative Example 2 Acrylic emulsion blended in the undercoat layer in Example 2 (Nippon Acrylic Co., Ltd., trade name Primal RM-5)
A heat-sensitive recording paper was prepared by performing the same processing as in Example 2 except for the following.

[0031]

According to the present invention, it has become possible to produce a heat-sensitive recording material having good image uniformity and excellent recording sensitivity at a high speed.

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41M 5/28-5/34

Claims (1)

(57) [Claims] 1. A heat-sensitive recording material comprising a support and at least one surface thereof laminated with an undercoat layer, a thermosensitive coloring layer utilizing a thermosensitive coloring reaction between a dye precursor and a color developer in that order.
The viscosity at 8800 rpm of Hercules viscometer is 2
A thermosensitive recording method comprising: applying an undercoat layer paint having a viscosity of not less than 0 cps and a viscosity of not less than 400 cps at 60 rpm of a BL viscometer on a support from a jet fountain, and then coating by controlling a coating amount with a blade. Material manufacturing method.