JP3102794B2 - Thermal recording paper - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a thermosensitive recording paper, and more particularly, to an improvement in appearance and a thermosensitive property of a thermosensitive recording paper containing deinked waste paper pulp as a support. About.

(Prior art) A thermosensitive recording method using a basic colorless dye and the basic colorless dye and an acidic substance which develops color when heated has characteristics such that a phenomenon process is unnecessary and hardware maintenance is easy. It is widely used for various facsimile machines, recorders of printers and measuring instruments, and the like.

At present, high-quality paper (paper that does not contain waste paper pulp) is used as a support for thermal recording paper. However, from the viewpoint of demand for cost reduction of thermal recording paper and reuse of paper pulp,
In the future, it is expected that paper containing waste paper pulp will be increasingly used as a support for thermal recording paper.

However, when a base paper containing waste paper pulp is used as a support for such a heat-sensitive recording paper, the whiteness of the support is reduced. For example, in the case of a support containing 40% of deinked newspaper waste paper pulp, the whiteness is reduced. It drops to the 60% range. On the other hand, high quality paper containing no waste paper pulp has a whiteness of 80% or more.

By blending waste paper pulp with the support in this way, the whiteness of the support is reduced, and the greater the blended amount of waste paper pulp, the greater the decrease in whiteness.

Therefore, when a heat-sensitive recording layer is provided on a support containing a large amount of waste paper pulp, the whiteness of the heat-sensitive recording paper is clearly lower than that obtained when the high-quality paper is used as the support, and the heat-sensitive recording paper using the high-quality paper as the support is used. Inferior to.

Further, when the thermal recording layer is provided directly on the support, the recording density becomes low when recording is performed using a thermal head, and when the recording is continued for a long time, coloring scum of the thermal recording layer adheres to the thermal head.

On the other hand, if the pigment or the binder is further increased in order to reduce the adhesion of scum to the thermal head, the recording density is reduced.

In addition, when deinked waste paper pulp is used as the support, the thermal recording paper is affected by the surfactant used in the deinking process of waste paper pulp, causing background fogging during high-temperature and high-humidity storage, fading of the recording part, and thermal decolorization. Problems such as the reliability of the thermal head being impaired due to missing dots due to contact with the head are caused.

On the other hand, 0.5 ~ 5μ on paperboard mainly composed of waste paper pulp
It is possible to provide a coating layer containing a white pigment and a binder
No. 58-25986. The white pigments used in JP-A-58-25986 include clay, calcium carbonate,
Inorganic pigments such as zinc oxide, aluminum hydroxide, talc, and inorganic clays such as activated clay, polystyrene, polyolefin, and urea formalin resin are exemplified.
The mere use of these pigments improves the appearance of the thermal paper somewhat, but does not improve the printing characteristics, running characteristics, etc.
Sometimes it gets worse.

(Problems to be Solved by the Invention) The present invention uses a support containing deinked waste paper pulp and has a whiteness that is not inferior to that of high-quality paper,
Another object of the present invention is to provide a thermosensitive recording sheet which is excellent in running property.

(Means for Solving the Problems) According to the present invention, when deinked waste paper pulp is used as a support, a pigment having a large volume oil absorption and a specific surface oil absorption are used. This is based on the finding that the above problem can be effectively solved by using a pigment coating layer having a whiteness of a specific value or more.

That is, the present invention provides a heat-sensitive recording paper having a heat-sensitive recording layer containing, as a main component, a colorless to light-colored basic dye and an acidic substance that forms a color when contacted with the basic dye. A paper support (excluding paperboard) with a whiteness of less than 80%, including deinked waste paper pulp, and a volume oil absorption of 1.5 ml /
cm ³ comprise more pigments, there is a surface oil absorption degree is 4.0 ml / m ² or more, the pigment coating layer, such as the whiteness of the coated surface of the heat-sensitive recording layer is at least 80%, the support and the heat-sensitive Another object of the present invention is to provide a thermosensitive recording paper provided between recording layers.

In this specification, the volumetric oil absorption refers to the oil absorption (JIS K
5101) and the specific gravity of the pigment, expressed in units of [ml / cm ³ ], and the surface oil absorption was determined by multiplying the pigment amount per unit area by the oil absorption of the pigment [JIS K 5101]. And expressed in [ml / m ² ]. In addition, whiteness refers to JIS P1823
The whiteness measured by "Hunter whiteness test method for paper and pulp".

In the present invention, deinked printed paper such as newsprint is used.

In addition, deinked waste paper pulp is generally made from a combination of the following three steps. (1) Disintegration: The waste paper is treated with a mechanical force and a chemical using a pulper to loosen it into a fibrous form, and the printing ink is peeled from the fiber.

(2) Dust removal: Removes foreign matter (such as plastic) and dust contained in waste paper.

(3) Deinking: The printing ink removed from the fiber is removed from the system by a flotation method or a washing method.

If necessary, bleaching can be performed simultaneously with deinking or in a separate step.

A support for a thermosensitive recording medium is formed by a conventional method using the thus obtained deinked waste paper pulp 100% or a mixture of deinked waste paper pulp and virgin pulp in an amount of 50% or less.

As the basic dye used in the thermal recording paper of the present invention,
For example, the following substances may be mentioned.

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-methylindol-3-yl) phthalide, 3,3-
Bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide,
3-bis (9-ethylcarbazol-3-yl) -6
Dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide,
Triallylmethane dyes such as 3-p-dimethylaminophenyl-3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydryl benzyl ether, Diphenylmethane dyes such as N-halophenyl-leuco auramine and N-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-
Spiro dyes such as benzyl-spiro-dinaphthopyran, 3-methyl-naphtho (6'-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran, rhodamine-B-anilinolactam, rhodamine (p-nitroanilino) lactam, Lactam dyes such as rhodamine (o-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-6-
Methoxyfluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluoran, 3- (N-ethyl-p-toluidino) -7-methylfluoran, 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-phenylaminofluor Orane, 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-iso-
Acylamino) -6-methyl-7-phenylaminofluoran, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-phenylaminofluoran,
-Pyrrolidino-6-methyl-7-phenylaminofluoran, 3-piperidino-6-methyl-7-phenylaminofluoran, 3-diethylamino-6-methyl-7-
Xylidinofluoran, 3-diethylamino-7- (o
-Chlorophenylamino) fluoran, 3-dibutylamino-7- (o-chlorophenylamino) fluoran,
3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, 3-dibutylamino-6-methyl-
Fluoran dyes such as 7-anilinofluoran;

The proportion of the basic dye in the total solid content of the coating liquid for forming the heat-sensitive recording layer is 1 to 30% by weight, preferably 5 to 25% by weight.

In addition, various types of inorganic or organic acidic substances that are colored upon contact with a basic dye are also known, for example, activated clay,
Acidic clay, attapulgite, bentonite, colloidal silica, inorganic acid substances such as aluminum silicate, 4-te
rt-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxyacetophenol, 4-tert-octylcatechol, 2,
2'-dihydroxydiphenol, 2,2'-methylenebis (4-methyl-6-tert-isobutylphenol), 4,
4'-isopropylidenebis (2-tert-butylphenol), 4,4'-sec-butylidenediphenol, 4-phenylphenol, 4,4'-isopropylidenediphenol (bisphenol A), 2,2'-methylenebis (4
-Chlorophenol), hydroquinone, 4,4'-cyclohexylidenediphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, novolak phenolic resin, 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- Aromatic carboxylic acids such as methylbenzyl) salicylic acid, 3,5-di-tert-butylsalicylic acid, 3-phenyl-5- (α, α-dimethylbenzyl) salicylic acid, and 3,5-di-α-methylbenzylsalicylic acid; And organic acid substances such as salts of these phenolic compounds and aromatic carboxylic acids with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin and nickel.

The proportion of the acidic substance in the total solid content of the coating liquid for forming the heat-sensitive recording layer is 5 to 50% by weight, preferably 10 to 40% by weight.

In the heat-sensitive recording material of the present invention, the use ratio of the color former and the color former in the recording layer is appropriately selected depending on the type of the color former and the color former used, and is not particularly limited. For example, when a basic colorless dye and an acidic substance are used, generally 1 to 50 parts by weight, preferably about 1 to 10 parts by weight of the acidic substance is used per 1 part by weight of the basic colorless dye.

In preparing a coating solution containing these substances, water is generally used as a dispersion medium, and the color former and the color former are dispersed together or separately by a stirring / pulverizer such as a ball mill, an attritor, or a sand grinder, and the coating is performed. It is prepared as a liquid. In this case, the dispersed particles should be as small as possible, specifically 2 μm.
It is desirable to disperse until the following particles are obtained.

In such a coating liquid, starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene / maleic anhydride copolymer, styrene / maleic anhydride copolymer as an adhesive,
Ethylene / acrylic acid copolymer, styrene / acrylic acid copolymer salt, styrene, butadiene copolymer emulsion and the like are used in an amount of about 10 to 40% by weight, preferably about 15 to 30% by weight of the total solid.

Furthermore, various auxiliaries can be added to the coating liquid, for example, sodium dioctyl sulfosuccinate,
Sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, alginate,
Examples thereof include dispersants such as fatty acid metal salts, benzophenone-based and triazole-based ultraviolet absorbers, other defoamers, fluorescent dyes, and coloring dyes.

If necessary, lubricants such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, ester wax, etc., kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine anhydrous silica, activated clay And inorganic pigments such as stearic acid amide, stearic acid methylene bisamide, oleic acid amide, palmitic acid amide, perfume oleic acid amide, coconut fatty acid amide, metaterphenyl, parabenzylbiphenyl, ester derivative of hydroxynaphthoic acid, dibenzyl terephthalate And sensitizers such as tribenzylamine and di-p-methylbenzyl oxalate.

The pigment used for forming the pigment coating layer of the present invention is not particularly limited as long as the volume oil absorption is 1.5 ml / cm ³ or more.For example, calcined kaolin, amorphous silica,
Synthetic magnesium silicate, aragonite calcium carbonate, titanium oxide, zinc oxide and the like. Among them, those having a volume oil absorption of 2.0 ml / cm ³ or more are preferable. As the binder used together with the pigment, for example, the same binder as used as an adhesive for heat-sensitive paints such as polyvinyl alcohol (PVA), casein, and starch can be used.

The ratio of the pigment and the binder used in the pigment coating layer is appropriately selected according to the type of the pigment and the binder used, and is not particularly limited. A pigment and a binder are prepared using a Cores, a three-roll mill, a sand grinder, and a ball mill so that the average particle size is 5 μm or less. The obtained coating composition for a coating layer is applied on a support so as to have a coating amount of 3 to 20 g / m ² , preferably 5 to 15 g / m ² .

The pigment coating layer surface oil absorbency of at least 4.0 ml / m ² or more, preferably 5.0 ml / m ² or more, the whiteness of the coated surface of the heat-sensitive recording layer at least 80% or more, preferably 82% or more It is to be.

(Effects of the Invention) According to the present invention, a heat-sensitive recording material was obtained using a support containing waste paper pulp, which was not inferior to high-quality paper, and was also excellent in color development characteristics and running properties.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.

Heat sensitive paint A liquid Black coloring basic paint 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-anilinofluoran (S-205: manufactured by Yamada Chemical) 9 parts by weight Polyvinyl alcohol 12% aqueous solution 15 Parts by weight 20% aqueous solution of polystyrene ammonium acrylate 0.7 parts by weight Water 30 parts by weight Liquid B 2,2-bis (4-oxyphenyl) propane 20 parts by weight Meta-terphenyl 20 parts by weight Polyvinyl alcohol 12% aqueous solution 50 parts by weight Polystyrene acrylic 20% aqueous ammonium acid solution 3 parts by weight Water 62.3 parts by weight Each liquid having the above composition was separately dispersed by a sand grinder until the average particle diameter became 2 μm or less.

Liquid C Light calcium carbonate 25 parts by weight 40% aqueous solution of sodium polyacrylate 1 part by weight Water 24 parts by weight Liquid C was dispersed for 10 minutes by a homomixer.

54.7 parts by weight of the liquid A prepared above, 155.3 parts by weight of the liquid B, and 50 parts by weight of the liquid C are mixed, and 33.3 parts by weight of a 30% zinc stearate dispersion,
% Aqueous solution and 130 parts by weight of water to obtain a heat-sensitive paint.

Example 1 50 g / m ^{2 of} rice tsubo consisting of deinked waste paper pulp 70% and NBKP 30%
A pigment coating layer composed of a pigment and a binder as shown in Table 1 was provided on a medium-grade paper having a whiteness of 63% so that the coating amount after drying the above-mentioned heat-sensitive paint was 6 g / m ^2. Coating,
Further, the surface of the recording layer was subjected to a surface treatment such that the Bekk smoothness was 500 seconds to obtain heat-sensitive recording papers of Examples 1 to 4 and Comparative Examples 3 to 10.

Next, a comparative example was prepared in the same manner as in Example 1 except that a pigment coating layer was not provided on the above-described medium-quality paper and high-quality paper of 50 g / m ² in U.S.P. comprising 80% of NBKP and 80% of LBKP, and a brightness of 83%. 1 and 2
Was obtained.

Table 1 shows the composition of the pigment coating layer and the volumetric oil absorption of the pigment,
Shows the value of surface oil absorption.

The whiteness and coloring characteristics of the thermal paper thus obtained were tested for adhesion of scum to the thermal head, and the results are shown in Table 2.

1. Coloring characteristics Evaluation was performed using a thermal tester TH-PMD (Okura Electric Co., Ltd.). This evaluation was performed under the following printing conditions.

Thermal head: KJT-256-8MGF1 (manufactured by Kyocera) Applied voltage: 24.0 V Pulse period: 2.0 msec Pulse time: 1.1 msec The coloring density at this time was measured by Macbeth densitometer RD-514. The higher the value, the higher the sensitivity.

2.Dust adhesion test 50% black ratio using a commercially available fax (FACOM FAX2000, manufactured by Fujitsu)
Was used to continuously print 100 sheets of A4 size paper, and after printing, the amount of deposits on the thermal head was visually determined.

◎ Very good ○ Good △ Somewhat good × Poor 3. Whiteness Performed according to JIS P8123 “Hunter whiteness test method for paper and pulp”.

Table 1 In the column of the composition and performance of the pigment coating layer, P represents the amount of the pigment, B represents the amount of the binder, PVA represents polyvinyl alcohol, and CW represents the coating amount.

 ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-58-25986 (JP, A) JP-A-62-240580 (JP, A) JP-A-2-172786 (JP, A) JP-A-2- 14182 (JP, A) JP-A-2-59386 (JP, A) JP-A-1-306669 (JP, A)

Claims (1)

(57) [Claims] 1. A thermosensitive recording paper having a colorless or pale-colored basic dye and a thermosensitive recording layer mainly composed of an acidic substance which forms a color upon contact with the basic dye on a support, the support is removed. A paper support (excluding paperboard) having a whiteness of less than 80%, including black ink pulp, containing a pigment having a volume oil absorption of 1.5 ml / cm ³ or more, and a surface oil absorption of 4.0 ml / m ² or more A thermosensitive recording paper, wherein a pigment coating layer is provided between the support and the thermosensitive recording layer such that the whiteness of the coated surface of the thermosensitive recording layer is at least 80% or more.