JP2766296B2 - Manufacturing method of thermal recording film - Google Patents

Description

The present invention relates to a method for producing a heat-sensitive recording film, and particularly to an excellent heat-sensitive recording film having no recording unevenness.

"Prior art" Conventionally, a thermosensitive recording method in which a color-forming image is obtained by contacting both color-forming substances by heat using a color-forming reaction between a color-forming agent and a color-developing agent that forms a color in contact with the color-forming agent. The body is well known. Generally, paper is used as the support of such a thermosensitive recording medium.

In recent years, the required performance quality has been diversified with the expansion of applications of the thermal recording medium. For example, high sensitivity, high density, image stability, stabilization of print pixels, and the like have been mentioned. A film may be used as a support for such a purpose.

When a heat-sensitive recording film is manufactured using a film as a support, the coating liquid is usually transferred to a film web by a plain roll, gravure roll, offset roll, or the like, and then the coating amount is adjusted and coated with an air knife, bar, blade, or the like. Although the surface to be coated has been made uniform, it is difficult to obtain a sufficiently uniform coated surface, and at present, an excellent thermosensitive recording film without coating unevenness has not been obtained.

"Problems to be Solved by the Invention" In view of the circumstances described above, the present inventors have conducted intensive studies to obtain a heat-sensitive recording film having a uniform and excellent heat-sensitive recording layer surface. After specifying the viscosity of the liquid and forming a coating film of the coating liquid on a gravure roll and / or an offset roll and transferring it to a running film, a smoothing process is performed with a rotating wire bar having a specific diameter. It has been found that a heat-sensitive recording film having extremely excellent smoothness and having no unevenness in the recorded image can be obtained.

"Means for Solving the Problems" The present invention relates to a heat-sensitive recording film in which a water-dispersion coating solution containing at least a color former and a color developer is coated and dried to form a heat-sensitive recording layer. In the manufacturing method, Broo
A coating film of the aqueous dispersion coating liquid having a kfield viscosity of 20 to 500 centipoise is formed on a gravure roll and / or an offset roll, and the coating film on the roll is transferred onto a continuously running film. This is a method for producing a thermosensitive recording film, characterized by performing smoothing with a rotating wire bar having a diameter of 18 mm or less.

`` Function '' As described above, the method of the present invention is such that the viscosity of the water-dispersed coating liquid that forms the heat-sensitive layer is in the range of 20 to 500 centipoise using a Brookfield viscometer, and the gravure roll and And / or forming a coating film on an offset roll, transferring the coating film on a continuously running film, and smoothing the transfer surface with a rotating wire bar having a diameter of 18 mm or less.

In the method of the present invention, the viscosity of the water-dispersed coating liquid for forming a heat-sensitive layer is a particularly important requirement, and a desired uniform coating layer film (surface) cannot be obtained by any treatment depending on the state of the viscosity. In the present invention, as one requirement, the viscosity of the water-dispersed coating liquid is specified to be 20 to 500 centipoise in Brookfield viscosity, preferably 30 to 300 centipoise, and only within this specific viscosity, smooth and uneven coating. No heat-sensitive recording film can be obtained for the first time. By the way, if the viscosity of the coating liquid is less than 20 centipoise, a mottling phenomenon will occur, and if it exceeds 500 centipoise, bar streaks will occur, deteriorating the commercial value.

Also, the coating layer surface transferred from the gravure roll and / or offset roll onto the film usually has an irregular shape as it is, and in general, a method of smoothing with an air knife or a blade can be considered. The method has a problem that it is difficult to obtain a uniform coated surface because it is difficult to adjust the smoothness of the coated surface, and it is difficult to adjust the coating amount and prevent the generation of streaks with the blade.

In the method of the present invention, surface smoothing is performed using a rotating wire bar, but if the diameter of the bar is too large,
Although the reason is not clear, it is not possible to obtain a uniform coating layer surface. The present inventors have focused on the dimensions of the rotating wire bar and made various studies, and as a result,
It has been found that a heat-sensitive recording film which is extremely uniform and free from recording unevenness can be obtained by specifying the thickness to 18 mm or less.

As described above, in the method of the present invention, the viscosity of the water-dispersed coating liquid and the diameter of the rotating wire bar are specified, and the desired effects of the present invention can be obtained only within this range.

Next, the composition of the heat-sensitive layer will be described. In the present invention, a coating composition for a recording layer generally used in the heat-sensitive recording material field can be applied, and the combination of the color former and the developer contained in the recording layer is not particularly limited. Any combination may be used as long as the two can be brought into contact with each other by heat to cause a color reaction. For example, a combination of a colorless to light-colored basic dye and an inorganic or organic acidic substance, stearic acid secondary Examples include a combination of a metal salt of a higher fatty acid such as iron with a phenol such as gallic acid, and further, various types of recording media obtained by heat, such as a thermosensitive recording material combining a diazonium compound, a coupler and a basic substance. Can also be applied to a thermosensitive recording medium.

However, the effect of the present invention is particularly exhibited in a combination of a basic dye and an acidic substance, and thus is particularly preferably applied to such a combination. Various types of colorless to light-colored basic dyes are known, and examples thereof include the following. 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p
-Dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindole) phthalide, 3,3-bis (1, 2-dimethylindol-3-yl)
-5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -6 -Dimethylaminophthalide, 3,3-bis (2-
Phenylindol-3-yl) -6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3- (1
-Methylpyrrole-3-yl) -6-dimethylaminophthalide and other triallylmethane dyes, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucouramine, N- Diphenylmethane dyes such as 2,4,5-trichlorophenyl leuco auramine, thiazine dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue, 3-
Methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran, 3-benzine-spiro-dinaphthopyran, 3-methyl-naphtho- (6'-methoxybenzo) -spiropyran, 3-propyl-spiro -Spiro dyes such as dibenzopyran, lactam dyes such as rhodamine-B anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran, 3- Diethylamino-7-methoxyfluoran, 3-diethylamino-
7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7
-Dimethylfluoran, 3- (N-ethyl-p-toluidino) -7-methylfluorane, 3-diethylamino-
7-N-acetyl-N-methylaminofluoran, 3-
Diethylamino-7-N-methylaminofluoran, 3
-Diethylamino-7-dibenzylaminofluoran,
3-diethylamino-7-N-methyl-N-benzylaminofluoran, 3-diethylamino-7-N-chloroethyl-N-methylaminofluoran, 3-diethylamino-7-N-diethylaminofluoran, 3- (N −
Ethyl-p-toluidino) -6-methyl-7-phenylaminofluoran, 3- (N-cyclopentyl-N-ethylamino) -6-methyl-7-anilinofluoran,
3- (N-ethyl-p-toluidino) -6-methyl-7
-(P-toluidino) fluoran, 3-diethylamino-6-methyl-7-phenylaminofluoran, 3-diethylamino-7- (2-carbomethoxy-phenylamino) fluoran, 3- (N-ethyl-N-isoamyl Amino) -6-methyl-7-phenylaminofluoran, 3- (N-cyclohexyl-N-methylamino)-
6-methyl-7-phenylaminofluoran, 3-pyrrolidino-6-methyl-7-phenylaminofluoran,
3-piperidino-6-methyl-7-phenylaminofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7- (o-chlorophenylamino) fluoran, 3-pyrrolidino-6
Methyl-7-p-butylphenylaminofluoran, 3
-N-methyl-N-tetrahydrofurfurylamino-6
-Methyl-7-anilinofluoran, 3-N-ethyl-
N-tetrahydrofurfurylamino-6-methyl-7-
And fluoran dyes such as anilinofluoran.

In addition, various inorganic or organic acidic substances which are colored upon contact with a basic dye are known in the art, and examples thereof include the following.

Activated clay, acid clay, attapulgite, bentonite, colloidal silica, inorganic acidic substances such as aluminum silicate, 4-tert-butyl nol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert -Octylcatechol, 2,2'-dihydroxydiphenol, 2,2'-methylenebis (4-methyl-6-tert-butylphenol),
4,4'-isopropylidenebis (2-tert-butylphenol), 4,4'-sec-butylidene diphenyl, 4-
Phenylphenol, 4,4'-isopropylidene diphenol (bisphenol A), 2,2'-methylenebis (4
-Chlorophenol), hydroquinone, 4,4'-cyclohexylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolak-type phenolic resins, phenolic compounds such as phenolic polymers, Benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid,
Terephthalic acid, 3-sec-butyl-4-hydroxybenzoic acid, 3-cyclohexyl-4-hydroxybenzoic acid,
3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3- (α-methylbenzyl) salicylic acid, 3-chloro-5- (α- Methylbenzyl) salicylic acid, 3,5-tert-butylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl)
Salicylic acid, aromatic carboxylic acids such as 3,5-di-α-methylhensyl salicylic acid, and these phenolic compounds, and aromatic carboxylic acids such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, nickel, etc. Organic acid substances such as polyvalent metal salts.

In the present invention, the use ratio of the color former and the color former in the recording layer is appropriately selected according to the type of the color former and the color former used, and is not particularly limited. When a colorless dye and an acidic substance are used, generally 1 to 50 parts by weight, more preferably about 1 to 10 parts by weight of the acidic substance is used per 1 part by weight of the basic colorless dye.

To prepare a coating liquid containing these substances, water is used as a dispersing catalyst, and a color former and a color former are dispersed together or separately by a stirrer such as an attritor or a sand mill, or a pulverizer. It is prepared to have a viscosity in the range of 20-500 centipoise. The average particle diameter of this coating liquid is preferably 2.5 microns or less from the viewpoint of suppressing clogging of the gravure roll, while
It is a preferable range from 15% or more to 2% by weight or less from the viewpoint of stabilization of a printing pixel.

In addition, a binder is usually blended in the coating liquid.
Examples of the binder include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, diisobutylene-maleic anhydride copolymer salt, Styrene-maleic anhydride copolymer salt, ethylene-acrylic acid copolymer salt, styrene-acrylic acid copolymer salt, styrene-butadiene copolymer emulsion, urea resin, melamine resin, amide resin, and the like. One or more of these are appropriately used. In that case, the amount added is 10
It is preferably about 70% by weight.

In addition, various auxiliaries can be appropriately added to the heat-sensitive recording layer coating liquid as needed, for example, sodium dioctyl sulfosuccinate, sodium dodecylbenzene sulfonate, lauryl alcohol sulfate-sodium salt, Dispersants such as alginates and fatty acid metal salts,
Benzophenone-based, triazole-based ultraviolet absorbers,
Other examples include an antifoaming agent, a fluorescent dye, and a coloring dye.

In addition, if necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, calcium carbonate, zinc oxide, aluminum oxide, titanium dioxide, silicon dioxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc ,
Inorganic pigments such as kaolin, clay, calcined clay, and colloidal silica, and organic pigments such as styrene microballs, nylon powder, polyethylene powder, and urea formalin resin filler can also be added. further,
A sensitizer may be added according to the purpose. Specific examples of sensitizers include, for example, fatty acid amides such as stearic acid amide, methylene bisamide stearate, oleic acid amide, palmitic acid amide, and coconut fatty acid amide;
Dibenzyl terephthalate, 1,2-di (3-methylphenoxy) ethane, 1,2-diphenoxyethane, 4,4'-ethylenedioxy-bis-benzoic acid diphenylmethyl ester, 1,1,3-tris ( 2-methyl-4-hydroxy-
5-tert-butylphenyl) butane, 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,
Hindered phenols such as 4'-butylidenebis (6-tert-butyl-3-methylphenol) and various known heat-fusible substances can be added.

The coating solution for the heat-sensitive recording layer thus prepared is coated on a film running through a gravure roll and / or an offset roll so that the weight after drying is 1 to 10 g / m ² and dried. And finished as a thermal recording film. In the present invention, in order to enhance the adhesion between the film and the heat-sensitive layer, a corona discharge treatment or an undercoat layer may be provided on the surface of the film in advance, or a pigment such as calcium carbonate or titanium oxide may be internally added to the film.

As the film used in the present invention, for example, a film made of polyester, polypropylene, polyimide, polyamide, cellulose acetate or the like having a thickness of 30 to 250 μm is preferably used.

"Examples" Hereinafter, the present invention will be described more specifically with reference to examples, but is not limited thereto. In the examples, "parts" and "%" indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 Preparation of solution A 3- (N-ethyl-N-iso-amylamino) -6-methyl-7-phenylaminofluoran 10 parts Dibenzyl terephthalate 20 parts Methyl cellulose 5 parts Water 65 parts This composition was subjected to sand milling. It was pulverized until the average particle size became 2 μm.

Solution B Preparation 4,4'-isopropylidene diphenol 30 parts Methyl cellulose 5 parts Water 65 parts This composition was pulverized with a sand mill until the average particle diameter became 2 μm.

Preparation of coating liquid 100 parts of liquid A, 100 parts of liquid B, 30 parts of silicon oxide pigment (trade name; Mizuka Seal P-527, manufactured by Mizusawa Chemical Co., Ltd.), aqueous dispersion of zinc stearate (trade name: Hydrin Z- 7-30, Chukyo Yushi Co., Ltd.) 30 parts, 20% polyvinyl alcohol aqueous solution 150
And 150 parts of water were mixed to prepare a coating liquid having a viscosity of 180 centipoise. The average particle size of the coating liquid was 2.3 μm, and that of 15 μm or more was 1.8% or less.

Formation of heat-sensitive layer The obtained coating liquid was subjected to corona discharge treatment to a thickness of 50 μm.
Was transferred onto a polyethylene terephthalate film using a gravure roll so that the coating amount after drying was 5 g / m ^2, and the transferred surface was smoothed with a wire bar having a diameter of 10 mm to obtain a thermosensitive recording film.

Example 2 Example 1 was repeated except that, in the preparation of the coating solution of Example 1, 150 parts of water was changed to 200 parts, and in forming the heat-sensitive layer, a wire bar having a diameter of 15 mm was used instead of a wire bar having a diameter of 10 mm. A heat-sensitive recording film was obtained in the same manner as described above.
The viscosity of the coating liquid at this time was 110 centipoise.

Example 3 A thermosensitive recording film was obtained in the same manner as in Example 1, except that the diameter of the wire bar used for forming the thermosensitive layer was changed from 10 mm to 5 mm.

Comparative Example 1 A thermosensitive recording film was obtained in the same manner as in Example 1 except that in preparing the coating liquid of Example 1, 150 parts of water was not used and a coating liquid having a viscosity of 980 centipoise was prepared.

Comparative Example 2 Thermal recording was conducted in the same manner as in Example 1 except that in preparing the coating liquid of Example 1, 300 parts of water was used instead of 150 parts of water to prepare a coating liquid having a viscosity of 15 centipoise. A film was obtained. In this case, a stable coated surface was not obtained.

Comparative Example 3 A thermosensitive recording film was obtained in the same manner as in Example 1 except that a wire bar having a diameter of 25 mm was used instead of a wire bar having a diameter of 10 mm in forming the heat-sensitive recording layer of Example 1. In this case, a smooth coating layer surface could not be obtained.

TV images were recorded on the thus obtained six types of heat-sensitive recording films using a heat-sensitive printer (SONY UP-701, TV printer), and the presence or absence of image unevenness was visually determined. Bar streaks on the surface of the obtained heat-sensitive recording film were visually determined. The results thus obtained are shown in Table 1.

〔Evaluation criteria〕

Image unevenness: ○; no image unevenness ×; image unevenness Bar streaks: ○; almost no bar streaks ×; bar streaks occurred "Effects" As is clear from the results in Table 1, the heat-sensitive recording films obtained in the examples of the present invention were excellent without image unevenness.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-40586 (JP, A) JP-A-61-291073 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/30 B05D 1/40

Claims (1)

(57) [Claims] 1. A method for producing a heat-sensitive recording film, wherein a water-dispersion coating liquid containing at least a color former and a color developer is coated on a film and dried to form a heat-sensitive recording layer.
A coating film of the aqueous dispersion coating liquid having a kfield viscosity of 20 to 500 centipoise is formed on a gravure roll and / or an offset roll, and the coating film on the roll is transferred onto a continuously running film. A method for producing a thermosensitive recording film, characterized by smoothing with a rotating wire bar having a diameter of 18 mm or less.