JP2894000B2 - 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]

The present invention relates to a thermosensitive recording material having a thermosensitive coloring layer utilizing a thermosensitive coloring reaction between a dye precursor and a color developer on at least one surface of a support. Viscosity at 8800 rpm is 20
After applying a thermosensitive coloring layer coating material having a viscosity of 60 cps or more (high shear viscosity) and a viscosity at 60 rpm of a BL viscometer of 400 cps or more (low shear viscosity) from a jet fountain to a substrate, the coating amount is controlled with a blade. This is based on the knowledge that image coating has uniformity and enables high-speed production.

As a coating method, a method using an air knife, a bar, a blade, or the like is generally known. However, 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.

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 a substrate in order to exhibit its performance.

[0010] There are four coating methods: a jet fountain, a die fountain, a roll application, and a 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, no coating amount is 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. Some of the blade coatings are roughly divided into chips, vents,
There are three types of rods, but in any case, a uniform layer structure cannot be obtained unless the paint properties within the scope of the present invention are satisfied.

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-aninofluoran, 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-α-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, that is, zinc stearate, aluminum stearate, calcium stearate, zinc oleate and the like.

Examples of the inorganic pigment 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 an adhesive. As the adhesive, polyvinyl alcohol, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride can be used as long as the fluidity of the present invention is obtained. It can be combined with acid copolymers, polyacrylic acid, polyacrylic acid, starch, casein, gelatin and the like. 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 liquid is applied on one surface of the sheet-like support in an amount of 3 to 8
g / m ² (dry) to form a heat-sensitive recording layer. 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 beating degree of the pulp is 400 to give a good slitter cutability.
ml (CSF) or more.

[0020]

The present invention will be further described by way of examples. Example 1 Dispersions A and B were prepared as coating liquids for a thermosensitive coloring layer. Preparation of Dispersion A A vertical sand mill (manufactured by Imex Co., Ltd.)
The mixture was placed in a sand grinder) and subjected to a dispersing and refining operation using glass beads having a diameter of 1.2 mm as a dispersion medium for 30 minutes. Subsequently, the composition was placed in a sand mill (Diafine mill, manufactured by Mitsubishi Heavy Industries, Ltd.). The mixture was charged 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 heat-sensitive 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% modified starch (trade name: Petrocoat C, manufactured by Nisseki Chemical Co., Ltd.)
8) 100 parts of an aqueous solution, 3% hydroxyethylcellulose (trade name: HEC, SE60, manufactured by Daicel Chemical Industries, Ltd.)
0) 30 parts of an aqueous solution were mixed and stirred to prepare a coating solution. This coating solution was weighed 50 g from a jet fountain.
/ M ² of high quality paper and coated with a blade (blade angle 20 °, blade thickness 0.508 mm) so that the coated amount after drying at a coating speed of 600 m / min is 4.5 g / m ² After controlling the amount, drying was performed to form a thermosensitive coloring layer. A thermal recording paper was manufactured using a super calendar at 800 seconds with a Oken type smoothness meter.

The recording sensitivity and image uniformity of the obtained thermosensitive recording paper 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.

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

Comparative Example 1 A heat-sensitive recording paper was prepared in the same manner as in Example 1 except that the hydroxyethyl cellulose compounded in the thermosensitive coloring layer in Example 1 was not added.

Comparative Example 2 A heat-sensitive recording paper was prepared in the same manner as in Example 2 except that the hydroxyethyl cellulose compounded in the thermosensitive coloring layer in Example 2 was not added.

[Table 1]

[0027]

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.

Continuation of front page (56) References JP-A-4-282286 (JP, A) JP-A-1-113280 (JP, A) JP-A-1-189369 (JP, A) JP-A-4-290789 (JP) JP-A-58-139760 (JP, A) JP-A-59-22684 (JP, A) JP-A-61-33260 (JP, A) JP-A-1-69676 (JP, U) (58) Field surveyed (Int.Cl. ⁶ , DB name) B41M 5/28-5/34

Claims (1)

(57) [Claims] 1. A thermosensitive recording material having a thermosensitive coloring layer utilizing a thermosensitive coloring reaction between a dye precursor and a color developer on at least one surface of a support.
After applying a thermosensitive coloring layer paint having a viscosity at 00 rpm of 20 cps or more and a viscosity at 60 rpm of a BL viscometer of 400 cps or more from a jet fountain to a substrate, the coating amount is controlled with a blade to perform coating. A method for producing a thermosensitive recording material.