JPS5889397A - Heat-sensitive recording sheet - Google Patents

Abstract

PURPOSE:To insolubilize a heat-sensitive recording sheet in water by using a combination of a diisobutyrene-maleic anhydride copolymer or its water-soluble salt and carboxymethyl cellulose or methyl cellulose as a binder for a heat- sensitive coloring layer and a supporter. CONSTITUTION:In a heat-sensitive coloring layer containing as main components a coloring agent, a developer and a binder, as a binder for the supporter, a combination of 1pt.wt. methyl cellulose or carboxymethyl cellulose and 1- 20pts.wt. a diisobutyrene-maleic anhydride copolymer or its water-soluble salt (e.g., ammonium salt) is used. For example, the ammonium salt of an aqueous solution of diisobutyrene-maleic anhydride copolymer and an aqueous solution of methyl cellulose are mixed in a heat-sensitive coloring liquid, and the mixture is uniformly coated on the supporter. Thus, water-proofness and dispersivity are raised and excellently uniform and durable film can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a heat-sensitive recording sheet containing a heat-sensitive coloring agent, a color developer, and a binder in a heat-sensitive coloring layer.

A general heat-sensitive recording sheet that is printed with a thermal head or a thermal pen is coated on a support such as paper or film with a thermal coloring agent such as lactam, spiropyran, or organic metal salt, bisphenol A, hydroquinone, etc. A heat-sensitive coloring layer containing a color developer and a binder as main components, and is manufactured by coating and drying an aqueous solution or aqueous dispersion containing these components for forming a heat-sensitive coloring layer on a support. There is. In this case, the binder is polyvinyl alcohol (Japanese Patent Publication No. 45-1403
No. 9), hydroxyethyl cellulose (% Kaisho 4g-1
7344), hydrophobic resins (JP-A-49-79250), carboxyl group-containing water-soluble resins (however, formaldehyde, glyoxal, chromium alum, melamine-formaldehyde resin, etc. are used in combination as water-resistant agents) (JP-A-49-79250) Water-soluble or water-dispersible (emulsion type) products such as No. 50-30539) are used. However, these binders are not only water-soluble, but even those with water-resistance additives have poor water resistance, so if the recording sheet or its recorded material gets wet with drinking water or rain, the former will lose color. In the latter case, the printed image may run or bleed, making it extremely unclear or difficult to read. Products using hydrophobic resins have drawbacks such as deterioration of thermochromic properties and adhesion of molten residue, and when a water-resistant resin is used in combination with a water-resistant resin, a crosslinking reaction occurs in the thermosensitive coloring layer forming solution.
．． In addition to the liquid coagulating, it is said that normal low-temperature drying (drying at a temperature of 100°C or lower, as heat-sensitive coloring layers are usually dried at a temperature of 100°C or lower, as high-temperature drying above 100°C may cause coloration) does not provide sufficient water resistance. There were drawbacks. In order to solve these drawbacks, various proposals have been made regarding water-resistant agents for water-soluble resins. For example, in JP-A-49-36343, a compound having two or more epoxy groups in one molecule is
JP-A No. 49-32646 describes a compound having two or more ethyleneimine groups in one molecule, and JP-A No. 52-7
No. 3047 discloses metal oxides such as zinc oxide and titanium oxide.

However, these water-resistant agents have the disadvantage that they inhibit the color development of heat-sensitive recording sheets, resulting in a decrease in color density.
Furthermore, when a pigment or the like is contained during coating, the dispersibility of the pigment or the like is poor and it is difficult to obtain a uniform coating film. JP-A-54-80136 discloses the use of hydroxyethyl cellulose and diisobutylene-maleic anhydride copolymer as a water-resistant binder, but this product tends to generate bubbles during coating, and It has the disadvantage that it is difficult to obtain a uniform coating film due to repellency and white spots caused by bubbles.

The object of the present invention is to eliminate the above-mentioned drawbacks caused by conventional binders and water-resistant agents, and to provide a heat-sensitive recording sheet that is particularly excellent in uniform coating properties and water resistance.

That is, the heat-sensitive recording sheet of the present invention is a heat-sensitive recording sheet in which a heat-sensitive color forming layer is provided on a support, the heat-sensitive color forming layer mainly consisting of a heat color forming agent, a color developer for the color forming agent, and a binder. It is characterized by using a combination of isobutylene-maleic anhydride copolymer or a water-soluble salt thereof and methylcellulose or carpoquine methylcellulose.

In the heat-sensitive coloring layer of the heat-sensitive recording sheet of the present invention, the binder consisting of diisobutylene-maleic anhydride copolymer or its aqueous salt and methylcellulose or carboxymethylcellulose used as a binder requires a water-resistant agent. It not only significantly improves the water resistance and coating properties of heat-sensitive recording sheets, but also improves color development, coating film strength, prevents generation of scum due to matching with thermal pens or thermal heads, and prevents color development due to pressure. is effective. Note that the binder of the present invention is preferably used in the form of a water-soluble salt such as an ammonium salt. The diinbutylene-maleic anhydride copolymer or its water-soluble salt is used in an amount of 1 to 20 parts by weight per 1 part by weight of carboxymethylcellulose or methylcellulose.

Other materials used for the heat-sensitive coloring layer may be the same as conventional ones. That is, the thermal color formers include crystal violet lactone, malachite green lactone, and 3,3-
bis(p-dimethylphenyl)-6-aminophthalide,
3,3-bis(p-dimethylaminophenyl)-6-P
-) Luenesulfonamide, 3-dimethylamino-6-
Medoxyfluorane, 3-diethylamine-6-methyl-7-chlorofluorane, 3-dibutylamino-6-
Methyl-7-chlorofluorane, 3-dimethylamino-6-methyl-7-phenylaminofluorane, 3-dimethylamino-7-(N-methyl-P-)luidino)fluorane, 3-diethylamino-7-penzyl aminofluora/, 3-methyl-di-β-naphthospiropyran,
Lactone, lactam or spiropyran dyes such as benzo-β-naphthospiropyran; 5 Long chain fatty acid iron salts such as ferric stearate; Ni such as acetic acid and stearic acid.

Examples include organic acid metal salts such as Co and Ag salts.

In addition, as a coloring agent, for example, 4-hydroxyphenoxy7)
”, 4-t-butylphenol, 4-hydroxyacetophenone, resorcin, α-naphthol, β-naphthol, thymol, catechol, hydroquinone, pyrogallol, phloroglucin, phloroglucucarboxylic acid, 4
, 4'-5ee-7' tylidene diphenol, 4.4'
-isopropylidecibis (2-t-butylphenol)
, 4 = t-octylcatechol, 2.2'-dihydroxydiphenyl, 2.2'-methylenebis(4-methyl-6-t-butylphenol), 2.2'-bis(4
Mechanical substances such as '-oxyphenyl)propane and 3,5-xylenol; Reducing substances such as indane, hydroquinone, and ethylene dithiourea; Inorganic acidic substances such as activated clay, silica, and bentonite. .

The heat-sensitive recording sheet of the present invention is manufactured by a conventional coating method. In this case, the amount of the coloring agent, developer, and binder used is 5 to 10.10 to 50.20 to 40%, respectively, based on the weight of the coloring layer.
% is appropriate. In addition, a white pigment, starch, wax-like substance, etc. can be added to the coloring layer.

Next, the present invention will be explained in more detail with reference to examples.0 Example 1 Solution A; Crystal violet lactone 20 parts by weight 5-thimethyl cellulose aqueous solution 101
1 water 6 (
IIIB liquid; Bisphenol A 20
Parts by weight 5 parts by weight of aqueous methyl cellulose solution 10 parts by weight Water
60 RiC
Liquid; N-stearylphenylamide 20 parts by weight 5-thimethylcellulose aqueous solution $10'!
water 60
NThe aforementioned liquids A, B, and C were each pulverized and dispersed in a ball mill for 24 hours, and then mixed in the following proportions to prepare a thermosensitive coloring layer forming liquid.

A liquid 1 part by weight B liquid
4 #C liquid
2 # This liquid was applied to the surface of high-quality paper (basis weight 50 g/mj) to a dry adhesion amount of 6117 m'' to form a heat-sensitive coloring layer. Obtain recording materials.

Next, when this heat-sensitive recording sheet was printed and recorded using a thermal printer equipped with a built-in thermal head, a clear blue image was obtained. Furthermore, when we conducted a water resistance test by immersing this record in water for 1 hour, we found that there was no falling off of the image or stickiness of the non-image area, and no falling off of the colored layer was observed even after rubbing back and forth with the fingertips 30 times. I couldn't.

Example 2 A heat-sensitive recording material with excellent coated surface uniformity was obtained by dispersing, preparing and coating in the same manner except for replacing the 5-polymer methyl cellulose aqueous solution in the can liquid of Example 1 with a 2% carboxyl methyl cellulose aqueous solution. When printed, a clear blue image was obtained. The water resistance of this recorded material was also excellent as in Example 1.

Comparative Example 1 A heat-sensitive recording material was prepared in the same manner as in Example 1, using isobutylene-maleic anhydride copolymer ammonium salt in place of the diisobutylene-maleic anhydride copolymer ammonium salt (20% aqueous solution) of Example 1. Obtained.

Comparative Example 2 Example 202%02% Using hydroxyethyl cellulose instead of calhokyfurmethylcellulose Example 2
A heat-sensitive recording material was obtained in the same manner as above.The properties of each of the heat-sensitive recording sheets obtained as described above in 9 above were as shown in the table below. The test method is as follows.

Uniform coating property: The sample is completely colored in an oven at 150°C and evaluated for blackness.

○: No white repellents (spots), △” 1 θ white repellents less than 1 m/within A-4, ×: White repellents larger than 1 cm (in A-4).

Water resistance: After soaking the sample in water for 1 hour, take it out.
Rub it back and forth with your fingertips 30 times to observe and evaluate the surface condition.

◯: No change, △: Both images slightly fall off L7, surface becomes sticky, X: Most of the image falls off, and non-image areas also fall off.

Thermochromic property: Temperature at which the sample starts to develop color under conditions of 2'q 7cm" with a heated iron piece for 1 second. Table-1 Patent applicant Toshiaki Ikeura, patent attorney representing Ricoh Co., Ltd. Procedural amendment (method) % formula % 1. Indication of the case 1981 Patent Application No. / eMello ρβ No. 2 Name of the invention Thermal Recording Sheet 1 Person making the amendment Relationship to the case Patent applicant address 1-3-6 Tsurimagome, Ota-ku, Tokyo Name (674) Ricoh Co., Ltd. Representative Dai
Takeshi Ue 4, agent address: 1-22-15 Kamiosaki, Tokyo Parts Ward
No.5, Date of amendment order Voluntary

Claims (1)

[Claims] (1) In a heat-sensitive recording sheet in which a heat-sensitive color forming layer is provided on a support, the heat-sensitive color forming layer is mainly composed of a heat color forming agent, a color developer for the color forming agent, and a binder, in which diisobutylene-anhydrous matte is used as the binder.
Thermosensitive recording sheet 0 characterized by using a combination of an inic acid copolymer or a water-soluble salt thereof and carboxylmethylcellulose or hamethylcellulose.