JPH02204086A - heat sensitive recording material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a heat-sensitive recording medium, and more specifically, a heat-sensitive coloring layer containing a colorless or slightly light-colored leuco dye and a color developer that causes the leuco dye to develop a special color under heat. The present invention relates to an improvement of a heat-sensitive recording material provided on an undercoat layer.

(Prior art and problems to be solved) A thermal recording method that uses a normally colorless or slightly light-colored leuco compound and a color developer that causes the leuco dye to develop a special color under heat does not require a developing process and requires no hardware maintenance. Because it has characteristics such as being easy to use, it is widely used in various printers, facsimile machines, recorders of measuring instruments, etc. As these devices become faster, high-speed recording is possible with low energy.
There is a demand for a thermosensitive recording material with excellent color development. In order to meet such demands, providing an undercoat layer on a support and further providing a heat-sensitive coloring layer thereon has already been disclosed in JP-A-54-23545 and JP-A-53-86229. ing.

By the way, when a pigment with a large oil absorption amount specified by the JIS K-5101 method is used, the sensitivity of the thermal recording medium improves [7
It has been found that the adhesion of debris to the head is greatly improved (Japanese Patent Application Laid-Open No. 86229/1983).

However, when a heat-sensitive color coating liquid is supplied onto an undercoat layer using a pigment with a large oil absorption amount, an aqueous solution such as a water-soluble binder liquid in the heat-sensitive color coating liquid is rapidly absorbed into the undercoat layer. As a result, the water-soluble binder K in the heat-sensitive coloring coating solution suddenly decreases, and the concentration of the heat-sensitive coloring coating solution increases.The water-soluble binder transferred to the undercoat layer fills the voids in the undercoat layer. In addition, as the amount of binder in the heat-sensitive coloring layer decreases, the surface strength of the heat-sensitive coloring layer itself decreases, causing color development due to pressure blur and scratches. It becomes easier.

Moreover, if extra binder is added to the heat-sensitive color coating solution to prevent this, the coating concentration of the heat-sensitive color coating solution will increase, decreasing the color development sensitivity and causing streaks in bar coating. In blade coating, the heat-sensitive coloring coating liquid reaches an immobilization point between the time it is applied and the excess coating liquid is scraped off, making streaks and scratches more likely to occur.

(Objective of the Invention) Therefore, the present invention provides a heat-sensitive recording material with improved surface strength and reduced adhesion of residue by reducing the absorption of the aqueous portion of the heat-sensitive color coating solution into the undercoat layer. The purpose is to

As a result of intensive studies to achieve the above object, the inventor has found that:
By reducing the transfer of the aqueous solution portion of the heat-sensitive coloring paint to the undercoat layer, that is, the support with the undercoat layer is
Absorption coefficient for water by Brist method (hereinafter simply referred to as Brist method) according to α51-87) (0.40 rd, / m□, lTl5 +/2 or less for a, and absorption coefficient for linseed oil by Brist method) The inventors have discovered that the above object can be achieved by setting the coefficient Ka to O, l Ord/roI · for the furnace 7 or more, and have arrived at the present invention.

(Means for solving problems) The present invention will be explained in detail below.

As the support, various sheet-like materials such as paper, synthetic paper, and plastic film are generally used.

Examples of R materials for undercoat use include aluminum oxide, titanium oxide, hydrous silicic acid, calcium silicate,
Sodium aluminosilicate, magnesium aluminosilicate,
Pigments such as calcined kaolin, diatomaceous earth, anhydrous silicic acid, aluminum silicate, and magnesium silicate are used.

As a binder for the undercoat layer, a water-soluble binder,
For example, starches, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol-71/, modified polyvinyl alcohol, styrene-maleic anhydride copolymer,
Examples include water-soluble binders such as ethylene-maleic anhydride copolymer, latex-based water-soluble binders such as styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, and methyl acrylate-butadiene copolymer.

The amount of binder to be used is determined taking into consideration the strength of the undercoat layer. Usually, the solid content is used in a proportion of 10 to 100 parts by weight per 100 parts by weight of the pigment.

Specifically, the Ka for water in the Bristo method is 0.4.
A method for reducing the value to 0 d/m'·m s l 72 or less is obvious to those skilled in the art, and is carried out, for example, by adding a sizing agent that exhibits a sizing effect to the undercoat layer. Substances that exhibit a size effect include, for example, acidic sizing agents and neutral sizing agents. Examples of acidic sizing agents include rosin-based sizing agents such as rosin, modified rosin, and rosin emulsion paste, and examples of neutral sizing agents include , self-fixing cationic sizing agents such as petroleum resin-based or acrylic-based sizing agents, and reactive sizing agents such as alkenylsuccinic anhydride or alkyl ketene dimer. The amount used is generally in the range of 0.01 to 20 parts by weight, preferably 0.5 to 10 parts by weight, per 100 parts by weight of the pigment.

Further, adjustment of the oil absorption coefficient is also obvious to those skilled in the art, and can be easily adjusted, for example, by using a pigment with a large oil absorption amount.

The undercoat layer is applied onto the support using an air knife coater, bar coater, blade coater, rod coater, or the like.

The heat-sensitive coloring layer usually contains a leuco compound, a color developer that causes the leuco compound to develop a specific color under heat, a binder, and a pigment.

As a leuco compound, it is usually colorless or light colored,
A substance that develops color by reacting with a color developer is preferred. For example, triphenylmethane type, triphenylmethane phthalide type,
Examples include various derivatives such as fluorane, leucoolamine, diphenylmethane, phenothiazine, phenoxazine, spiropyran, indoline, and indigo. Specifically, the following can be exemplified.

Crystal violet lactone (blue), 3-diethylamino-6-methyl-7-anilinofluorane (black)', 3-(N-ethyl-P-)luideino)-6-methyl-7-anilinofluorane ( black), 3-diethylamino-6-methyl-7-(ortho-, para-dimethylanilino)fluoran (black), 3-pyrrolidinol 6
-Methyl-7-anilinofluorane (black), 3-piperidine-6-methyl-7-anilinofluorane (black>, 3-(N-cyclohexyl-N-methylamino)-
6-Methyl-7-anilinofluorane (black), 3-diethylamino-7-(ortho-chloroanilino)fluoran (black), 3-diethylamino-7-(meta-trifluoromethylanilino)fluoran (black), 3-diethylamino-6-methyl-chlorofluorane (red)
, 3-diethylamino-6-methyl-fluorane (red), 3-cyclohexylami/-6-chlorofluorane (orange), 3-(N-inamyl-N-ethylamino)
-6-methyl-7-anilinofluorane (black), 2.
2-bis(4-(6'-(N-cyclohexyl-N-methylamine)-3'-methylspiro [phthalide-3,
9'-xanthine]-2'-ylamino]phenyl)propane (black), etc.

The color developer is a substance that is solid at room temperature, softens or dissolves when heated, and develops color when it comes into contact with the leuco compound,
For example, 4-tert-butylphenol, 4-phenylphenol, bisphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, methyl-4
-Hydroxybenzoate, 4'-hydroxyacetophenone, 4-tertiaryoctylcatechol, 2.2'
Dihydroxydiphenyl, 2+2'-methylenebis(
4-Chlorophene, /-l), 4.4'-sec-butylidene diphenol, 4.4'-isopropylidene bis(2-methylphenol), 4.4'-isopropylidene bis(2,6-dimethylphenol) ), benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, dibenzyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, benzyl-4-hydroxyphenylacetate, or resorcin monobenzoate.

As the binder, a wide variety of binders conventionally known for use in thermosensitive coloring layers can be used. Moreover, it may be the same as the binder of the undercoat layer.

As a pigment, oil absorption is 8 as specified in JIS K~5101.
0Wf! /100g or more is preferred, but the pigment is not limited thereto, and pigments used in conventional heat-sensitive recording materials such as calcium carbonate, barium sulfate, and aluminum hydroxide can be used.

Various auxiliary components can be added to the heat-sensitive coloring layer as necessary. Such additives include, for example, head wear inhibitors and anti-sticking agents such as higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, paraffin oxide, polyethylene, polyethylene oxide, stearamide, and waxes such as castor wax. In addition, as sensitivity improvers, fatty acid amides such as stearic acid amide, metaterphenyl, parabenzyl biphenyl, esters of hydroxynaphthoic acid, tribenzylamine naphthalene derivatives, dibenzylthelinophthalate, etc. are used as storage stabilizers. Examples include water resistance agents, phenolic resins, dispersants such as sodium dioctyl sulfosuccinate, ultraviolet absorbing agents such as benzophenone and benzotriazole, surfactants, and fluorescent dyes.

The heat-sensitive color forming layer is prepared by using a heat-sensitive color forming coating liquid containing each of the components described in (A) in the same manner as in the preparation of the undercoat layer.

The application of the heat-sensitive coloring coating liquid is preferably carried out in a continuous process subsequent to the application of the underfoot layer, but the invention is not limited thereto.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

However, all parts and percentages shown in the examples are based on weight.

Example 1 Formation of undercoat layer Non-grade silica (Mizukasil P527 manufactured by Mizusawa Chemical Industry ■)
100 parts by weight of 12% aqueous solution of PVA 333,3
parts by weight, 33.4 parts by weight of water, and a styrene-maleic acid-based sizing agent (Sunsizer SΔ501).
4 parts by weight, dispersed for 10 minutes with a Coles disperser, and coated with a test blade coater at 50g/
It was coated on high-quality paper having a basis weight of m' at a coating weight of 6 g/rn' and dried to form an undercoat layer on the support.

Formation of thermosensitive coloring layer The following solutions A and B were prepared respectively.

50 parts by weight of liquid A, 50 parts by weight of acrylamide water-soluble resin (TY-121, solid content 20%) manufactured by Showa Denko, and 30 parts by weight of a 30% zinc stearate aqueous dispersion 1f3
Amorphous silica (oil absorption 150
20 parts by weight (mg/100g) were gradually added and mixed. Next, 150 parts by weight of Solution B was added to this Solution A, and 35 parts by weight of water was further added to prepare a heat-sensitive coloring coating liquid.

A liquid coloring leuco dye (3-(N-ethyl-N-isoamyl))
Amino-6-methyl-7-anili/fluoran) (S-205 manufactured by Yamada Chemical) 10 parts by weight water
It was prepared by dispersing 8 parts or more of components using a sand grinder until the average particle size was 1 μm.

B liquid bisphenol A, 18 parts by weight meta-
Terphenyl 22 parts by weight Polyvinyl alcohol (12% aqueous solution) 50 parts by weight Ammonium acrylate (20% aqueous solution) 3 parts by weight 1 part water
It was prepared by dispersing 57 parts by weight or more of the ingredients using a sand grinder until the average particle size was 1 μm.

The heat-sensitive coloring coating solution prepared in this way was coated on the support provided with the undercoat layer using a test blade coater at a coating amount of 5 g/m.Next, it was dried and further calendered. By doing this, a heat-sensitive recording material having a Bekk smoothness of the recording surface of 600 seconds was obtained.

Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the pigment in the undercoat layer was replaced with calcined kaolin (Anciles).

Example 3 A thermosensitive recording material was obtained in the same manner as in Example 1 except that PVA was replaced with casein and no sizing agent was used.

Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 1 except that Signside 5A501 was not used in Example I.

Comparative Example 2 A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the pigment of the undercoat was replaced with Charcoal PC.

○Evaluation (1) For the support provided with an undercoat layer, the Blist method (J, Tapp 1 paper pulp test method Nα5N-
The absorption coefficients for water and linseed oil were measured according to 87).

(2) Printing characteristics Using a thermal facsimile tester (Model MF-1 manufactured by Matsushita Electronic Components), an applied voltage of 20. OV and pulse width Q, 3m
The color density obtained by printing at 1.4 ms and 1.4 ms was measured using a Macbeth densitometer RD514.

(3) Surface strength The surface strength was examined using commercially available cellophane tape (Shichiro Beer test).

(4) Using a thermal sensitivity tester MP-1 for the adhesion of residue to the head, the applied voltage was 20, OV.
Then, 500 lines were printed continuously under the conditions of a pulse width of 1.41 Tls, and the condition of the head was observed.

The results are shown in Table 1 below.

As can be seen from Table 1, the water absorption coefficient Ka of the support having an undercoat layer based on the Bristo method is 0.40.
dl m'-ms'' or less, the absorption coefficient Ka for linseed oil using the same method is 0.15 ml/m, '・mS
By setting the ratio to 1/2 or more, an excellent heat-sensitive recording material was obtained in which the surface strength was maintained and the adhesion of residue to the head was prevented without deteriorating the sensitivity.

Claims (1)

[Claims] In a heat-sensitive recording material in which an undercoat layer containing a pigment and a binder is provided on a support, and a heat-sensitive coloring layer provided thereon, the support having the undercoat layer is
Bristow method (J. TAPPI paper pulp test method No.
51-87), the absorption coefficient Ka for water is 0.
．． 40ml/m^2・ms^1^/^2 or less, and the absorption coefficient Ka for linseed oil is 0.10ml
/m^2・ms^1^/^2 or more.