JPH10147059A - Heat-sensitive recording body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent wetting blocking or the like problem, by forming a protecting layer by using silicon modified polyvinyl alcohol and also glyoxal and epichlorohydrin as a hardener in a heat-sensitive recording body having a heat- sensitive coloring layer and the protecting layer set on a supporting body. SOLUTION: A heat-sensitive recording body which can record images according to a heat-sensitive recording method has a heat-sensitive coloring layer and a protecting layer set on a supporting body. The protecting layer is formed with the use of silicon modified polyvinyl alcohol and also glyoxal and epichlorohydrin as a hardener. The silicon modified polyvinyl alcohol used is polyvinyl alcohol including silicon in molecules which is produced by introducing silicon into polyvinyl alcohol or polyvinyl acetate with the use of a sililating agent, i.e., by a post modification method or the like. A compounding amount of glyoxal as the hardener is 10-30 pts.wt. based on 100 pts.wt. of silicon modified polyvinyl alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive recording medium on which an image can be recorded by a thermosensitive recording method, and more particularly, to a water-wetting blocking property of a protective layer provided on a thermosensitive recording layer.
The present invention relates to improvement of wet rub characteristics and stability of a protective layer paint.

[0002]

2. Description of the Related Art In general, a thermosensitive recording medium has a thermosensitive coloring layer formed on a support, and the thermosensitive coloring layer is heated by a thermal head, a hot pen, a laser beam, or the like to form a color in the thermosensitive coloring layer. The agent reacts instantaneously to form a recorded image. For example, JP-B-43-4160 and JP-B-4 Sho 4
It has been widely known from, for example, JP-A-5-14039.

[0003] These heat-sensitive recording media have the advantages that a recorded image can be formed by a relatively simple device, maintenance is easy, and noise during recording is small. It is applied to a wide range of fields, such as recorders, facsimile machines, printers for terminals such as computers, POS printers, automatic ticket vending machines, and bar code label printers. Especially in recent years,
The use of heat-sensitive recording materials is expanding to various types of tickets, receipts, ATMs for banks, and meter reading for gas and electricity. For this reason, there has been no problem with heat-sensitive recording materials in the past. Strict characteristics are being demanded.
That is, the properties required for the heat-sensitive recording medium include, for example, resistance to fading of a recorded image, background fog, and the like due to weather resistance and chemical resistance. It may be used outdoors and in rainy weather, and is required to be resistant to water.

On the other hand, conventional heat-sensitive recording materials include plasticizers such as phthalic acid diesters such as dibutyl phthalate, aliphatic dibasic acid esters and phosphoric acid triesters contained in vinyl chloride cases, salad oils and hand creams. Contacting with oils and fats, organic solvents such as ethyl alcohol and toluene, etc., has the disadvantage that the recorded image is discolored or the background is colored. In order to overcome such disadvantages, a protective layer has been conventionally provided on the heat-sensitive coloring layer. As a component constituting the protective layer, a water-soluble polymer such as polyvinyl alcohol or starch is used. Used as the main component.

For this reason, when a thermosensitive recording medium having a protective layer is used outdoors and in rainy weather, if the thermosensitive recording media after recording come into contact with each other immediately after being wet with water, the thermosensitive recording surface and the back surface or the thermosensitive recording surfaces of the thermosensitive recording surfaces are contacted. In the worst case, the heat-sensitive recording paper peels off the paper layer, causing a problem that the recorded information cannot be read. Adhesion of the back surface with water droplets causes blocking, resulting in a problem such as poor recording paper feeding.

In order to solve this problem, as a method of imparting water resistance to the protective layer of the heat-sensitive recording material, a cross-linking agent which reacts with such a water-soluble polymer is used in combination. However, when a protective layer is formed, it is not possible to impart thermal energy such that a sufficient cross-linking reaction occurs, and when a highly reactive cross-linking agent is used, a cross-linking reaction occurs in the coating liquid and the viscosity of the coating liquid is reduced. There is a problem that the coating is remarkably increased and coating cannot be performed.

In order to solve such a problem, it has been proposed to introduce a functional group which enhances reactivity into a water-soluble polymer. For example, JP-A-56-126193, JP-A-59-106995, and JP-A-59-1698
No. 85, Japanese Patent Application Laid-Open No. 62-264990, and the like have been proposed, but even if these modified polyvinyls are used, the water-wetting blocking property is insufficient.

Although the use of silicon-modified polyvinyl alcohol for the protective layer is a technique known in Japanese Patent Application Laid-Open No. 58-193189, water resistance cannot be imparted when used alone.
To compensate for these disadvantages, glyoxal is used in silicon-modified polyvinyl alcohol.
No. 91, and Japanese Patent Application Laid-Open No. 05-185718. However, glyoxal alone has low stability of the paint, and problems remain in wet rub characteristics. Further, JP-A-8-183252 proposes mixing chitosan and glyoxal in silicon-modified polyvinyl alcohol for the protective layer. However, even in this proposal, the stability of the coating material is low, and the obtained heat-sensitive recording material is liable to yellow. And the like.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a heat-sensitive recording material which has a high coating stability of a protective layer, does not cause problems such as blocking of water when used outdoors in rainy weather, and has excellent water resistance. The purpose is to provide.

[0010]

In order to solve the above problems, the present invention employs the following constitution. That is, the present invention
A support, a thermosensitive coloring layer formed on the support, and a thermosensitive recording medium having a protective layer formed on the thermosensitive coloring layer, wherein the protective layer uses silicon-modified polyvinyl alcohol,
Further, the present invention is a thermosensitive recording medium characterized by using glyoxal and epichlorohydrin in combination as a curing agent.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The silicon-modified polyvinyl alcohol used in the present invention may be any polyvinyl alcohol containing silicon in the molecule. As the production method, a method described in JP-A-58-193189 is generally used. That is, a post-modification method in which silicon is introduced into polyvinyl alcohol or polyvinyl acetate using a silylating agent, or a method in which a vinyl ester and a silicon-containing olefin monomer are copolymerized and saponified. In any case, the ratio as a residue of the silicon-containing monomer is preferably 0.01 to 10 mol%, particularly preferably 0.1 to 2.5 mol%. The saponification degree is 7
0-100 mol% is preferred. The polymerization degree is 3000 to 30
00, preferably 600-3000.

The amount of the silicon-modified polyvinyl alcohol used for the protective layer in combination with glyoxal, which is a curing agent, is in the range of 3 to 50 parts by weight, preferably 10 to 100 parts by weight of the silicon-modified polyvinyl alcohol. From 30 to 30 parts by weight are used. Further, epichlorohydrin is used in an amount of 3 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the silicon-modified polyvinyl alcohol. In addition, all of the above compounding amounts are pure component weight ratios not including water or a solvent.

[0013] The protective layer may have improved running properties and imparted writability.
For the purpose of imparting printing properties, an inorganic or organic pigment may be added. Examples of the pigment used include silicate earth, talc, kaolin, calcined kaolin, calcium carbonate, aluminum hydroxide, aluminum carbonate, magnesium carbonate, and titanium oxide. Inorganic pigments such as zinc oxide and amorphous silica, and organic pigments such as urea resins are used. In this case, it is sufficient that the pigment is contained in an amount of 5 to 60% by weight based on the total solid content of the protective layer.

Further, various additives usually used for the thermosensitive recording medium, for example, a dispersant such as sodium polyacrylate, a surfactant such as sodium dioctyl sulfosuccinate, an antifoaming agent such as fatty acid monoglycenide, a fluorescent agent, etc. Dyes and coloring pigments, waxes such as paraffin, paraffin oxide, polyethylene, polyethylene oxide, steramide, caster wax and the like can also be added.

The support used in the present invention is not particularly limited. For example, high quality paper, recycled paper, matte paper, oil resistant paper, coated paper, art paper, cast coated paper, finely coated paper, resin laminated paper, Polyolefin-based synthetic paper, synthetic resin film and the like can be used as appropriate. If necessary, an intermediate layer containing a pigment and a binder as main components may be provided between the support and the heat-sensitive coloring layer, and a back layer for curl adjustment and antistatic treatment may be provided.

The coloring component of the heat-sensitive coloring layer on the support may be any coloring component capable of forming a recorded image by heating. For example, an electron-accepting substance represented by a leuco dye and a phenolic substance , A reaction between an imino compound and an isocyanate compound, a reaction between a long-chain fatty acid iron salt and a polyhydric phenol, and the like. Specific examples of these combinations are described in, for example, JP-A-54-118845. The coating amount of the protective layer is 0.5 to 8 g / dry solid content.
m ² , preferably 1 to 4 g / m ² , and the coating amount of the heat-sensitive coloring layer is 2 to 2.
10 g / m ^2, preferably from 3 to 6 g / m ^2.

<Stability test of paint> The paint of the obtained protective layer was allowed to stand for 3 days, and the separation of the paint was observed. The evaluation criteria are as follows. ：: No separation. ×: There is separation.

<Water Wet Blocking Test Method> The obtained heat-sensitive recording material was cured for 24 hours in an environment of 40 ° C. and 30%, and then a Canon Handy Terminal Printer HT90 was used.
The test was performed by printing at 00. Drop a drop of water on the recording surface of the heat-sensitive recording medium after recording, fold the recording medium in half so that the recording surface is on the inside, and put 100 g / c on the recording medium on which the water droplet is dropped.
m ^{2 under} a load of 20 ° C and 65% RH for 24 hours.
Thereafter, the recording surface was peeled off and the blocking was evaluated. The evaluation criteria were as follows. ：: No blocking ×: Blocking occurred, a part of the recording layer was broken, and it was difficult to read the record XX: Blocking was large and peeled from the paper layer

<Wet Love Test> The obtained heat-sensitive recording medium was cured in an environment of 40 ° C. and 30% for 24 hours, and then a drop of water was dropped, and the film was reciprocated 5 times with a finger to evaluate the water resistance of the coating film. . ：: The coating film was not removed. Δ: Slightly removed. X: A coating film is removed. Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[0020]

【Example】

 <Example 1> <Preparation of heat-sensitive coating liquid> Liquid A: 3-dibutylamino-6-methyl-7-anilinofluoran 10 parts by weight Polyvinyl alcohol: 12% aqueous solution 26.7 parts by weight Ammonium polystyrene acrylate: 20% aqueous solution 1.6 parts by weight Water 21.3 parts by weight Liquid B: 30 parts by weight of 4-hydroxy-4'-isopropoxydiphenylsulfone 30 parts by weight of di (p-methylbenzyl) oxalate Polyvinyl alcohol: 12% aqueous solution 60 parts by weight Polystyrene ammonium acrylate: 20% aqueous solution 3.6 parts by weight Water 78 parts by weight

The solution A has a mean particle size (mean diameter determined by a laser diffraction / scattering particle size analyzer [LA910] manufactured by Horiba Seisakusho Co., Ltd., LA910) manufactured by HORIBA, Ltd .; Was dispersed until the average particle diameter became 0.8 μm. A adjusted above
Liquid: 59.6 parts by weight, Liquid B: 201.6 parts by weight and 1
83.3 parts by weight of 2% polyvinyl alcohol, water 2
1.3 parts by weight were mixed and stirred to prepare a hot coating liquid. The obtained heat-sensitive coating solution was applied to a high-quality paper of 50 g / m ² of rice tsubo using a test bar coater so that the coating amount after air-drying was 5 g / m ² , dried and applied to form a heat-sensitive recording layer.

<Formation of Protective Layer> A silicon-modified polyvinyl alcohol (R-1130:
350% by weight of a 12% aqueous solution of Kuraray), silica (Mizukasil-527: manufactured by Mizusawa Chemical Industries)
Parts, 30% zinc stearate dispersion (hydrin D-5)
23: 33.3 parts by weight of Chukyo Yushi, 25 parts by weight of glyoxal (40% aqueous solution), epichlorohydrin (W
S-570: 40 parts by weight of a 12.5% aqueous solution of Japan PMC) and 300 parts by weight of water were mixed and agitated, and the protective layer coating solution was applied by a test bar coater to 3 g / m ² and dried to protect. A layer was formed. Thereafter, a gloss calendering treatment was performed so that the surface Bekk smoothness was about 500 seconds to obtain a thermosensitive recording medium.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that epichlorohydrin was not used in forming the protective layer in Example 1.

Comparative Example 2 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that 80 parts by weight of epichlorohydrin was used without forming glyoxal in forming the protective layer of Example 1.

<Comparative Example 3> The procedure of Example 1 was repeated, except that 12.5 parts by weight of an 80% aqueous solution of melamine / formaldehyde (Sumilez Resin 613: manufactured by Sumitomo Chemical) was used in place of glyoxal in forming the protective layer. A thermosensitive recording medium was obtained in the same manner as in Example 1.

Comparative Example 4 The procedure of Example 1 was repeated, except that 20 parts by weight of a 50% aqueous solution of a polyamide polyurea resin (Sumilez Resin 636: manufactured by Sumitomo Chemical) was used in place of glyoxal in forming the protective layer of Example 1. In the same manner as in Example 1, a thermosensitive recording medium was obtained.

[0027]

[Table 1]: Evaluation results

[0028]

As is clear from Table 1, the coating stability of the protective layer is high, and the heat-sensitive recording material of the present invention is a heat-sensitive recording material excellent in both the water blocking property and the wet rub property.

Claims (1)

[Claims] 1. A thermosensitive recording medium having a support, a thermosensitive coloring layer formed on the support, and a protective layer formed on the thermosensitive coloring layer, wherein the protective layer uses silicon-modified polyvinyl alcohol, A thermosensitive recording material further comprising a combination of glyoxal and epichlorohydrin as a curing agent.