JPH0214181A - heat sensitive recording material - Google Patents

Abstract

PURPOSE:To eliminate the occurrence of a rope-bond-shaped wrinkle or texture blush on the occasion of a calendar processing and to improve color-developing sensitivity and density by a method wherein an undercoat layer containing a white pigment, a water-soluble integrating agent, ammonium nitrate and dicyandiamide is provided between a paper support and a thermal color developing layer. CONSTITUTION:As for a white pigment used for an undercoat layer, kaoline, natural silica, magnesium hydroxide or the like is mentioned, and as for a water-soluble integrating agent, roasted dextrin, starch ester, starch ether, casein, gelatin or the like is mentioned. The use ratio (weight ratio) of ammonium nitrate is within a range of 0.1 to 10 parts to 100 parts of the white pigment, while the use ratio of dicyandiamide is within a range of 1 to 30 parts to 100 parts of the water-soluble integrating agent. The water-soluble integrating agent of 2 to 40 parts is used based on 100 parts of the white pigment. The undercoat layer is applied by a coating system using an air knife, a blade, a roll or others, and the amount of a coat is 1 to 15g/m<2> in a dried weight and, preferably, within a range of 3 to 10g/m<2> in view of texture blush, color-developing sensitivity, density, etc.

Description

Detailed Description of the Invention (A) Industrial Application Field The present invention relates to a heat-sensitive recording material on which recording is performed using a thermal head, a thermal pen, etc. The present invention relates to a heat-sensitive recording material provided with an undercoat layer.

(B) Prior art Thermal recording materials are materials in which a thermosensitive coloring layer that develops color when heated is provided on a support such as paper, synthetic paper, or plastic film, and is used in thermal printers for calculators, comviator terminals, etc. It is widely used as a recording material for thermal pen recorders in medical measuring equipment, thermal facsimile machines, automatic ticket vending machines, etc.

Thermosensitive recording materials usually contain a color-forming substance, such as a lactone, lactam, or spiropyran-based color-forming leuco dye that is colorless or light-colored at room temperature, and a color-forming substance that develops color when heated together with the color-forming leuco dye, such as naphthol, catechol, resorcinol,
4.4'-isopropyritine diphenol, 4.4'-
After pulverizing and dispersing cyclohexylidene diphenol, benzoic acid, p-7 alephenol, etc. using a ball mill, sand mill, etc. to a desired particle size, a binder is added and mixed, and if necessary, a white pigment, It was produced by applying a coating solution for forming a heat-sensitive coloring layer prepared by adding an antifoaming agent and a waterproofing agent to a support such as paper and drying it.

The heat-sensitive recording material thus obtained is heated with a heat-generating resistor, a heat head made of nichrome wire, a heat pen, or the like to form a colored image.

In order to obtain high color development sensitivity and density with less energy in the above-mentioned heat-sensitive recording materials, or to reduce residue deposits on the thermal head, an undercoat layer containing inorganic or organic pigments and various compounds is added to the paper. It has been proposed to provide the coloring layer between the support and the heat-sensitive coloring layer.

Proposals for obtaining high color development sensitivity and density include, for example, JP-A-53-86229 and JP-A-54-23545.
No. 1, JP-A-56-27394, JP-A-59-
174390 and the like.

Furthermore, as proposals for ultra-high color development sensitivity and reduction of herad scum adhesion, for example, JP-A No. 61-89883 contains polystyrene and silicon oxide in the undercoat layer, and JP-A No. 61-193880 has an oil absorption of 100 m. /100F
JP-A-61, containing the above inorganic pigments in the undercoat layer.
For example, the undercoat layer may contain the same color developer and pigment having an oil absorption of 100 tons as in the heat-sensitive color forming layer of Publication No. 274989.

Currently, it is possible to form a so-called two-layer structure by coating these intermediate layer materials on a support such as paper with a dry solid content of 3 to 201β (dry solid weight) depending on the purpose of use, and then providing a heat-sensitive coloring layer thereon. Common.

(C) Problems to be Solved by the Invention The above-mentioned support is mainly a paper support, on which an undercoat layer and a heat-sensitive coloring layer are laminated, and the smoothness is increased with a supercalender etc. to make it resistant to thermal head. However, the paper support has uneven basis weight, and the cellulose fibers are thick and thin, long and short, uneven in papermaking (unevenness), and non-uniform orientation. The area becomes colored and becomes wrinkled. Furthermore, for calcined kaolin, natural silica, synthetic silica, silica alumina, etc., which have high oil absorption, this phenomenon is remarkable, and the so-called background capri, in which the entire heat-sensitive coloring layer develops color, occurs.

As a method to improve these problems, JP-A-61-1
No. 1286, a film is formed between the paper support and the thermosensitive coloring layer by applying a polymer as a first intermediate layer, and then forming a film with an apparent specific gravity of 0.
．． A composition mainly composed of a pigment of 5 f/al or less is provided as the second intermediate layer. JP-A No. 61-229589 discloses a method in which a first intermediate layer containing polyvinyl alcohol as a main component is provided between the paper support and the heat-sensitive coloring layer, and a first intermediate layer containing hydrophobic polymer fine particles as a main component is further provided thereon. There have been proposals to laminate a second intermediate layer, and the inventor's experiments have shown that the occurrence of background fogging is reduced and the effect is seen, but the coloring sensitivity is reduced.

CD) Purpose of the Invention The purpose of the present invention is to provide an undercoat layer on a paper support and a thermal coloring layer (1), and even if it is calendered, (1) there will be no wrinkles on the A-eyes or background capri, and there will be no color development. An object of the present invention is to provide a heat-sensitive recording material that can improve sensitivity and density.

(E) Means for solving the problem, that is, the inventor provided an undercoat (U) containing a white pigment, a water-soluble binder, ammonium nitrate, and dicyandiamide between the paper support and the thermosensitive coloring layer. According to
The present invention was based on the knowledge that a heat-sensitive recording material that does not cause line wrinkles or background fogging even after calendering treatment and that has improved color development sensitivity and density can be obtained.

The water-soluble binder used in the undercoat layer of the present invention may be mixed with a hydrophobic binder, a water-resistant agent, etc., if necessary.

The white pigment used in the undercoat layer of the present invention includes:
Examples include kaolin, calcined kaolin, natural silica, synthetic silica, silica-alumina, clay, calcium oxide, calcium carbonate, magnesium oxide, magnesium carbonate, magnesium hydroxide, and the like. Among these, the effects of the present invention are remarkable when calcined kaolin, natural silica, synthetic silica, silica-alumina, etc. with high oil absorption are used.

Examples of the water-soluble binder used in the undercoat layer of the present invention include starches such as roasted degistrin, oxidized starch, alpha starch, and starch esters such as phosphated starch, acetate-esterified starch, and nitrate-esterified starch. , allyl etherified starch,
Starch ethers such as methyl etherified starch, carboxymethyl etherified starch, carboxyethyl etherified starch, hydroxyethyl etherified starch, hydroxypropyl etherified starch, cationic starch, and proteins such as casein, gelatin,
Examples include soybean protein.

The usage ratio (weight ratio) of ammonium nitrate used in the undercoat layer of the present invention is 0 to 100 parts of white pigment.
．． In the range of 1 to 10 parts, if it is less than 0.1 part, it will be less effective in preventing rope wrinkles and skin capri, and if it is used in excess of 10 parts, no significant improvement will be obtained.

The ratio of dicyandiamide used in the undercoat layer of the present invention is in the range of 1 to 30 parts of dicyandiamide per 100 parts of the water-soluble binder. If the amount is less than 1 part, no effect will be obtained in preventing skin capri, and if it is more than 30 parts, the binding force of the water-soluble binder will decrease.

The ratio (weight ratio) of the water-soluble binder and white pigment used in the undercoat layer of the present invention is 2 to 40 parts of the water-soluble binder to 100 parts of the white pigment. If it is less than 2 parts, it will be less effective in preventing line wrinkles and scalp capri, and if it is more than 40 parts, the color development sensitivity will decrease.

The hydrophobic binder used in the undercoat layer of the present invention is a latex emulsion, which is a hydrophobic polymer such as styrene-butadiene, acrylic, or vinyl acetate.

The undercoat layer of the present invention is applied by a coating method such as an air knife, a blade, or a roll. The coating amount is 1 to 15% on dry ti-, preferably 3 to 102β based on the background capri, color development sensitivity, density, etc.
is within the range of

The heat-sensitive coloring order provided on the undercoat layer of the present invention mainly consists of a leuco dye and a color developer, but also a binder and, if necessary, waxes, a sensitivity improver, a metal soap, and a water resistant agent. is mixed with the above white pigment.

The leuco dye used in the present invention is not particularly limited as long as it is used in general pressure-sensitive recording paper, heat-sensitive recording paper, etc. Specific examples include (1) triarylmethane compounds such as 3.3-bis(p-dimethylaminophenyl)-6-dimethylamino 7thallide (crystal violet lactone), 3.3-bis(p- dimethylaminophenyl)7thalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindole-3
-yl)7talido, 3-(p-dimethylamino7enyl)-3-(2-methylindol-3-yl)7talido, 3-(p-dimethylaminophenyl)-3-(2-phenyl) indol-3-yl) phthalide, 3.3-bis-(1,2-dumedelindol-3-yl)-5-dimethylamino7thalide, 3.3-bis-(1,2-dimethylindole-3 -yl)-6-dimethylamino 7thalide, 3,3-bis-(9-ethylcarbazole-3-
yl)-5-dimethylaminophthalide, 3,3-bis-
(2-phenylindol-3-yl)-5-dimethylaminophthalide, 3-p-dimethylamino722-3
-(1-Methylpyrrole-2-ylk-6-dimethyl-aminophthalide, etc.): (2) As diphenylmethane compounds, 4,4'-bis-dimethylaminopenzhydrin pendyl ether, N-herophenyl leukoola (3) As a xanthine compound,
Rhodamine B-anilinolactam, Rhodamine B-p-
Nitroanilinolactam, Rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-phenylfluorane, 3- Diethylamino-7-3,4-dichloroanilinoneluorane, 3-diethylamine-7-(2
-chloroanilino)fluoran 3-diethylamine-
6-Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl-
tolylamino-6-methyl-7-anilinofluorane,
3-Ethyl-tolylamino-6-methyl-7-phenylfluoran, 3-diethylamino-7-(4-nitroanilino)fluoran, etc. = (4) Thiazine compound and shite, hendiylleucomethylene blue, p-nitropenzoylroy Cometelene blue, etc.: (5) Spiro-spirotic compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-cyclolose spiro-dinaphthopyran, and 3-benzyl spiro-dinaphthopyran.
Examples include toviran, 3-methylna7)-(3-meth)oxy-benz)-spiropyran, 3-propyl-spiro-dipenzopyran, and mixtures thereof.

These are determined by the application 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. Specifically, as phenols,
p-octylphenol, p-tert-butylphenol, p-phenylphenol, 1.1-bis(p-
hydroxyphenyl)propane, 2.2-bis(p-hydroxyphenyl)furopane, 1.1-bis(p-hydroxyphenyl)pentane, 1.1-bis(p-hydroxy7enyl)hexane, 2,2 -bis(p-hydroxyphenyl)hexane, 1,1-bis(p-hydroxyphenyl)-2-ethyl-hexane, 2.2-'x(
Examples include 4-hydroxy-3,5-dichlorophenyl)propane.

Examples of aromatic carboxylic acid derivatives include p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid, 3,5-di-methylbenzylsalicylic acid, and carvone. Examples of acids include these polyvalent metal salts.

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

Examples of metal soaps include polyvalent metal salts of higher fatty acids, ie, zinc stearate, aluminum stearate, calcium stearate, zinc oleate, and the like.

Sensitivity improvers include those with a sharp melting point of 80 to 140°C and good thermal responsiveness, such as benzoic acid and terephthalic acid esters, naphthalene sulfonic acid esters, and naphthyl. Ether derivatives, anthryl ether derivatives, aliphatic ether sensitizers, phenanthrene, fluorene, and other sensitizers can be used. The waxes mentioned above can also be used as sensitizers.

(F) In a heat-sensitive recording material using a working paper or the like as a support, an undercoat layer containing a white pigment, a water-soluble binder, ammonium nitrate, and dicyandiamide is provided between the support and the heat-sensitive coloring layer, thereby eliminating knot wrinkles. It is possible to obtain a heat-sensitive recording material that does not cause background fog and has excellent color development sensitivity and density.

(G) Examples Preferred embodiments and excellent effects of the present invention will be specifically explained below using the most typical examples. In addition, all parts below represent parts by weight.

Example 1 Dissolution method of oxidized starch (MS-3800) MS-38
00 (Nippon Shokuhin Kako) 100 parts dicyandiamide
1 part water 2
Put 99 parts of the above into a 1 ton stainless steel container, disperse with cold water, stir and dissolve in a water bath that maintains a liquid temperature of 80°C or higher for 60 minutes, then cool to room temperature to obtain oxidized starch (pure oxidized starch ratio of about 99%) 25 Create a 9% aqueous solution.

10 parts of 10% sodium hexametaphosphate was added to 300 parts of water, and synthetic silica (Mizusawa chemical layer force 1/hP-5
After adding and dispersing 100 parts of 27 (oil absorption 140d/100f), the above oxidized starch containing dicyandiamide (
After adding and stirring 8.1 parts of 25% water bath solution (MS 3800) and 42 parts of 48% carboxylated styrene-butadiene copolymer latex (DL-620 manufactured by Asahi Kasei), 9 parts of 25% ammonium nitrate water bath solution was added to form an undercoat. It was used as a coating liquid for layer formation. Apply this coating liquid to tsubo i-40f/rr.
? An undercoat layer was formed by applying the coating to a high-quality paper using an air knife coater and drying it so that the coating amount was 50% (dry weight solid content).

On the other hand, as a heat-sensitive coating liquid, 100 parts of 3-diethylamino-6-methyl-7-anilinofluoran, 10% polyvinyl alcohol, was used as liquid A.
250 parts Solution B 4.4'-Impropylidene diphenol 100 parts 10% polyvinyl alcohol 250 parts Solution C 2-benzyloxynaphthalene 100 parts 10% polyvinyl alcohol 250 il SD solution Calcium carbonate 100 parts 10% polyvinyl alcohol 250 parts A, B,
Each of the C% and D solutions was dispersed for 4 hours using a paint conditioner, and %A:B:C:D=1:5:
They were mixed at a weight ratio of 3:2 to create a heat-sensitive coating solution. This heat-sensitive coating liquid was applied to the high-quality paper provided with the above-mentioned undercoat layer using an air knife coater so that the coating amount was 5 f/d (dry weight solid content), dried at 60°C, and then Peck smoothness is 300-500 with super calendar
The thermosensitive recording paper was finished in seconds.

The background fog of this heat-sensitive recording paper was measured using a Hunter whiteness meter, and line wrinkles were visually observed and rated as O@×. (○ mark...
Almost none, @ mark...few, X mark...there) Also,
This thermal paper was printed using a thermal printing experiment device manufactured by Matsushita Electronics Components and equipped with a thin film head at a head voltage of 0.45 W/dot.
1 line recording time 39m5/l, scanning? The pulse width was set to 1.0.
1.2.1.5.2.0 msec and the print density was measured using a Macbeth densitometer.The measured values of color development sensitivity and -degree are shown in Table-■.

Example 2゜MS-3800 100 parts Dicyandiamide 15 parts Water 285 parts The above was placed in a 1 ton stainless steel container, dispersed with cold water, stirred and dissolved in a water bath maintained at 80°C or higher for 60 minutes, and then cooled to room temperature. A 25% aqueous solution of oxidized starch (with a pure oxidized starch ratio of about 87%) was prepared.

10 parts of 10% sodium hexametaphosphate was added to 300 parts of water, and 100 parts of synthetic silica (Mizukasil P-527) was added.
After adding and dispersing 69 parts of the above 25% aqueous starch oxide solution containing dicyandiamide and 48% carboxylated styrene-butadiene copolymer latex (DL-62
Example 1 except that after adding and stirring 10.4 parts of ammonium nitrate, 20 parts of an aqueous solution of 25% ammonium nitrate was added to obtain a coating solution for forming an undercoat layer. Create and measure thermal paper in the same manner as in step 9.

Example 3 MS-3800 100 parts Dicyandiamide 30 parts Water 270 parts The above was placed in a 1 ton stainless steel container, dispersed with cold water, stirred and dissolved for 60 minutes in a quarter bath kept at a temperature of 80°C or higher, and then cooled to room temperature. , prepare a 25% aqueous solution of oxidized starch (approximately 77% pure oxidized starch).

Add 10 parts of 10% sodium hexametaphosphate to 300 parts of water, and add 100 parts of synthetic silica (Mizukasil P-527).
After adding and dispersing 208 parts of a 25ts aqueous solution of oxidized starch containing the above dicyandiamide and stirring, 40 parts of an aqueous 25ts ammonium nitrate solution was added to prepare a coating solution for forming an undercoat layer except for Example 1. ．． Thermal paper was prepared and measured in the same manner as above.

Example 4 Casein (2 sealants 1 to 5 people Arajit 1 method) Casein 100 parts Dicyandiamide 15 parts Sodium hydroxide 5 parts Water 280 parts The above was placed in a stainless steel container No. 16, dispersed with cold water, and heated to 80°C or higher. The mixture was stirred and dissolved in a water bath for 60 minutes, and then cooled to room temperature to prepare a 25% aqueous casein solution (with a pure casein ratio of approximately 83%).

10 parts of 10% sodium hexametaphosphate was added to 300 parts of water, and 100 parts of synthetic silica (Mizukasil P-527) was added.
After adding and dispersing 72.3 parts of the above casein 25ts aqueous solution containing dicyandiamide, 48 parts
% carboxylated sterene butadiene copolymer latex (DL-620) was added and dispersed, and 20 parts of a 25% ammonium nitrate aqueous solution was added to form an undercoat)8.
Example 1 except that the forming coating liquid was used. Thermal paper was prepared and measured in the same manner as above.

Comparative Example 1 10 parts of 10% sodium hexametaphosphate was added to 300 parts of water, and 100 parts of synthetic silica (Mizukasil P-527) was added.
After adding and dispersing parts of oxidized starch (MS-3800
) 40 parts of 25% aqueous solution, 48% carboxylated styrene-butadiene copolymer latex (DL-620) 20.
Example 1 except that 8 parts were added and dispersed to form a coating solution for forming an undercoat layer. Thermal paper was prepared and measured in the same manner as above.

Comparative example 2゜Comparative example 1. A thermal paper was prepared and measured in the same manner as in Example 1, except that 20 parts of a 25% aqueous ammonium nitrate solution was added to the coating solution for forming an undercoat layer.

Comparative example 3゜Example 2. Example 1 except that the ammonium nitrate in the coating solution for forming undercoat layer M was omitted and the coating solution for forming an undercoat layer was used. Thermal paper was prepared and measured in the same manner as above.

Table - ■ In Table - ■, background fogging was measured with a Hunter whiteness meter, rope wrinkles were visually observed, and marked as ○, ■, or ×.

(O mark: Almost none, @ mark: Few, × mark...
・Yes) Color development sensitivity and density are measured using a g-thermal printing experimental device with a thin film head manufactured by Matsushita Electronics Components, using a head voltage of 0.45W.
/ dot, l line recording time 30 m5/l, scanning line density 8 x 3.85 dots/mm, pulse width 1.0.
1.2.1.5.2. These are the measured values of color development sensitivity and density obtained by printing at Qmsec and measuring the print density using a Macbeth densitometer.

(H) Effect of the invention As is clear from the examples, by providing an undercoat layer containing a white pigment, a water-soluble binder, ammonium nitrate, and dicyandiamide between the paper support and the thermosensitive coloring layer, seam wrinkles and texture can be reduced. A heat-sensitive recording material was obtained that did not generate capri and had excellent color development sensitivity and density.

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive coloring layer containing a leuco dye and a color developer as main components is provided on a paper support, a white pigment and a water-soluble binder are placed between the support and the heat-sensitive coloring layer. , a heat-sensitive recording material comprising an undercoat layer containing ammonium nitrate and dicyandiamide.