JPH04301493A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material, which has high color- developing sensitivity and excellent head matching and from which uniform distinct image recording having high density is obtained. CONSTITUTION:An undercoating layer containing sodium silicate aluminum is formed between a supporter and a thermal color-developing layer mainly comprising leuco dyes and a developer color-developing said leuco dyes on heating in a thermal recording material.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material having improved properties by providing an undercoat layer between a support and a heat-sensitive coloring layer.

0002

[Prior art and its problems] Heat-sensitive recording materials (thermal paper) are materials that can be heated with a thermal head, a thermal pen, a laser beam, etc. to cause a dye and a color developer to react instantaneously, resulting in a recorded image. No. 43-4160, Special Publication No. 45-14039
There is disclosure in the No. 2 publication, etc. Such heat-sensitive recording materials allow recording to be obtained using relatively simple equipment and are easy to maintain;
It has advantages such as no noise generation, and can be used as a measuring recorder,
fax machines, printers, computer terminals,
It is used in a wide range of fields such as labels, ticket vending machines, etc. In particular, as facsimiles become faster and printouts from computer terminals become faster, there is a need for heat-sensitive recording materials that have high sensitivity, that is, develop deep colors with low energy.

Various proposals have been made to increase the sensitivity of heat-sensitive recording materials. For example, (1) compounds that dissolve at a lower temperature than dyes and color developers and have a high ability to dissolve both ( (2) Reducing the content of components that do not participate in the coloring reaction in the thermosensitive coloring layer, such as fillers and binders (3)
Calendar treatment can improve the surface smoothness of the heat-sensitive recording layer.

[0004] These methods certainly improve the color development sensitivity, but the color development temperature decreases due to the addition of thermofusible substances and the content of fillers and binders decreases, and background fogging occurs due to a decrease in the surface strength of the thermosensitive color layer. , lack of strength against rubbing,
This causes so-called sticking, such as head dirt and running noise during running. Furthermore, if the smoothness is improved by calendering, the color development sensitivity will be improved, but sticking will occur and background fogging will also occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a heat-sensitive recording material that has high color development sensitivity, excellent head matching, and is capable of recording uniform, high-density, clear images.

[0006]

[Means for Solving the Problems] As a result of intensive research to achieve the above object, the present inventors have found that by providing an undercoat layer containing sodium aluminum silicate between the support and the heat-sensitive coloring layer. The inventors have discovered that a heat-sensitive recording material with good color development sensitivity and excellent head matching properties can be obtained, leading to the present invention.

That is, the present invention provides a heat-sensitive recording material in which a heat-sensitive coloring layer is provided on a support, the heat-sensitive coloring layer having a colorless or light-colored leuco dye and a color developer that causes the leuco dye to develop color when heated. and the heat-sensitive coloring layer, sodium aluminum silicate, preferably oil-absorbing (JIS K 622
Based on the test method specified in 0.75ml/100
The object of the present invention is to provide a heat-sensitive recording material characterized in that it is provided with an undercoat layer containing sodium aluminum silicate (having a numerical value of not less than g).

The main components used in the heat-sensitive recording material of the present invention will be specifically explained below, but are not limited thereto.

Examples of the leuco dye include colorless to light-colored triphenylmethane-based, fluoran-based, diphenylmethane-based, thiazine-based, and spiropyran-based compounds.

For example, crystal violet lactone, 3-diethylamino-7-methylfluorane, 3-di-n-butylamino-7-methylfluorane, 3-(N
-ethyl-iso-amylamino)-7-methylfluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-anilino Fluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-dibutylamino-7-(2-chloroanilino)fluoran, 3-diethylamino-7-
(3-chloroanilino)fluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N-
Ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3-(N-methylcyclohexylamino)
-3-methyl-7-anilinofluorane, 3-piperidino-3-methyl-7-anilinofluorane, and the like.

[0011] As the color developer, phenolic compounds, organic acids or metal salts thereof, hydroxybenzoic acid esters, etc. are preferable, such as phenol, p-t-butylphenol, p-phenylphenol, naphthol, p-
Hydroxyacetophenone, 2,2-dihydroxydiphenol, 4,4-isopropylidene (2-t-butylphenol), 4,4-isopropylidene diphenol, 4,4-cyclohexylidene diphenol,
Examples include novolac type phenol resin, benzoic acid, pt-butylbenzoic acid, p-hydroxybenzoic acid, p-hydroxybenzoic acid benzyl ester, p-hydroxybenzoic acid methyl ester, and the like.

Pigments that can be used in the heat-sensitive coloring layer include diatomaceous earth, talc, carrion, calcined carrion, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea-formalin resin, etc. Can be mentioned.

In the present invention, the sodium aluminum silicate used in the undercoat layer provided between the support and the thermosensitive coloring layer is preferably oil-absorbing sodium aluminum silicate, such as commercially available Zeolex series from Zeofinn. You can use the ones listed below. The oil-absorbing sodium aluminum silicate used in the present invention is defined by JIS
Based on the test method specified in K 6220, 75m
Refers to items with a numerical value of 1/100 g or more. The amount of sodium aluminum silicate used in the undercoat layer is 2
g/m2 or more, preferably 5 g/m2 or more. If the amount of sodium aluminum silicate used exceeds 15 g/m2, the amount of binder will be relatively reduced and the strength of the heat-sensitive recording material will tend to decrease, which is not preferable. The method of providing the undercoat layer between the support and the heat-sensitive coloring layer is not particularly limited, and a general method can be used. For example, the undercoat agent and the binder are mixed and stirred using a dissolver type homomixer or the like. An example of this method is to prepare an undercoat paint and apply this paint to a support using an applicator.

[0014] In addition to the above-mentioned sodium aluminum silicate, components commonly used in undercoat layers can be used in the undercoat layer. Such components include inorganic fillers such as talc, kaolin, calcium carbonate, silicon oxide, and titanium oxide, organic fillers such as urea-formalin resin, styrene-methacrylic acid copolymer, polystyrene resin, and foamable plastics. .

[0015] As the binder used in the present invention,
Starch, hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, water-soluble binders such as styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, styrene-butadiene copolymer Examples include latex-based water-insoluble binders such as polymers, acrylonitrile-butadiene copolymers, and methyl acrylate-butadiene copolymers.

In addition to the above-mentioned components, the heat-sensitive recording material of the present invention contains higher fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, paraffin oxide, polyethylene, polyethylene oxide, Waxes such as stearic acid amide and castor wax, dispersants such as sodium dioctyl sulfosuccinate, ultraviolet absorbers such as benzophenone and benzotriazole, surfactants, fluorescent dyes, etc. can be used in combination.

Paper is mainly used as the support for the heat-sensitive recording material of the present invention, but various nonwoven fabrics, plastic films, synthetic papers, metal foils, etc., or composite sheets made of a combination of these may also be used as desired.

[0018]

[Effect] The heat-sensitive recording material of the present invention is characterized by providing an undercoat layer containing sodium aluminum silicate between the support and the heat-sensitive coloring layer, and has high coloring sensitivity and excellent head matching properties. It is a heat-sensitive recording material that can record uniform, high-density images.

[0019]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited thereto. All parts and percentages shown in the examples are based on weight.

Examples 1 and 2 and Comparative Examples 1 to 4 1 part of the various undercoating agents shown in Table 1 and 2 parts of a 10% polyvinyl alcohol aqueous solution as a binder were mixed, and the mixture was heated at 2000 to 3000 revolutions using a dissolver type homomixer. So 2
The mixture was stirred for 0 to 30 minutes to obtain an undercoat paint. This paint was applied to commercially available high-quality paper (weighing: 50 g/cm) using an automatic film applicator manufactured by Yasuda Seiki.
2) was coated at about 6 g/m2.

[0021]

[Table 1]

[0022] Next, solutions A and B shown below were each separately pulverized in a sand mill until the average particle size became 2 μm or less. Separately, solutions C and D were stirred for 20 to 30 minutes at 2000 to 3000 rotations using a dissolver type homomixer to form a paint. Mix these A, B, C and D solutions 2:1
Mix and stir at a ratio of 0:5:3 (weight ratio) to make a heat-sensitive paint, and add 6g of the dry coating layer to the undercoat layer coated paper.
/m2 and dried to obtain a thermal paper of the present invention.

Solution A 3-(N-ethyl-iso-amylamino) 10 parts
-7-Methylfluorane 10% polyvinyl alcohol aqueous solution
Part 10 Water

10 parts B liquid 4
,4-isopropylidenediphenol
10 parts Stearic acid amide
10 copies 10%
Polyvinyl alcohol aqueous solution
40 parts C liquid calcium carbonate

20 parts 10% polyvinyl alcohol aqueous solution
40 parts D liquid fine powder silica

20 parts water

80 copies
The thermal paper obtained as described above was evaluated for dynamic color density and head matching. The results are shown in Table 2. Dynamic color density and head matching were evaluated using a printing tester manufactured by Okura Electric Co., Ltd. Print density was measured using a Macbeth RD914 type densitometer.

[0024]

[Table 2]

As is clear from Table 2 above, the heat-sensitive recording material of the present invention has high dynamic color development sensitivity, improves background texture, and has excellent head matching properties.

Claims (2)

[Claims] Claim 1. A heat-sensitive recording material comprising, on a support, a heat-sensitive coloring layer containing a colorless or light-colored leuco dye and a color developer that causes the leuco dye to develop color when heated; A heat-sensitive recording material characterized in that an undercoat layer containing sodium aluminum silicate is provided between the layers. 2. The heat-sensitive recording material according to claim 1, wherein the sodium aluminum silicate is oil-absorbing sodium aluminum silicate.