JPH0197682A - Thermosensitive recording medium - Google Patents

Abstract

PURPOSE:To provide reliable, recording paper while preventing cohesion, gelling, and smearing of a coating material, and also static electricity, by a structure comprising a plastic film coated thereon with a thermosensitive coloring layer, a first overcoating of conductive material formed on the coloring layer, and a second overcoating composed mainly of a film-forming polymer binder formed on the first overcoating. CONSTITUTION:A thermosensitive recording paper is composed of a double- coated layer, which includes a first overcoating containing conductive material to prevent charging and a second overcoating for improving image reliability. The conductive material in the first overcoating may be of ionic conduction or electronic conduction. The material of ionic conduction may be sodium chloride, while the materials of electronic conduction includes silver, copper, aluminum, etc. The film-forming polymer binder for the second overcoating may be a polyvinyl alcohol. A base material may be composed of polyester film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer.

[Prior art]

In recent years, with the increase in the amount of information, and social demands such as resource saving, labor saving, and pollution-free production, various recording methods have been put into practical use and improved in the information recording field. Among them, thermal recording materials The thermal recording method uses (1) primary color development that does not require a developing process, (2) the hardware is simple and compact, and maintenance costs are low; (3) the sheet itself has a feel similar to that of plain paper. Due to its relatively low cost, it is widely used in computer output, medical measurement recorder fields, facsimile fields, printer fields, and PO8.
It has been put to practical use in travel labels, tickets for vending machines, etc. The heat-sensitive recording material used in such a method includes a heat-sensitive coloring layer containing a colorless or light-colored leuco dye having a lactone, lactam, or spiropyran ring and an acidic substance, such as an organic acid or a phenolic compound, on a support. (Special Publication No. 43-4160, No. 45-1)
No. 4039, various publications, etc.) are publicly known. However, the above-mentioned leuco-based heat-sensitive recording materials have the drawbacks of poor stability of recorded images and easy discoloration6.
For example, there is the problem that the recorded image will fade when it comes into contact with oil or plasticizers (dioctyl phthalate, etc.) in plastic films, and solving this problem is a major technical challenge for this type of recording material. It has become.

In the past, several methods have been proposed to solve this problem, such as in heat-sensitive coloring layers.

The stability of the heat-sensitive coloring layer is increased by containing a large amount of resin with good water and chemical resistance, and the stability of the heat-sensitive coloring JeJ is increased by containing a resin that hardens with heat or light in the heat-sensitive coloring layer. In addition to the above, there are also those in which a resin protective layer is formed on the surface of the heat-sensitive coloring layer to protect the heat-sensitive coloring layer from the effects of chemicals and water.

On the other hand, there is also a growing demand for high-strength thermosensitive recording sheets, etc., in which the support is replaced with a plastic film, such as a polyester film, instead of conventional plain paper, and the strength of the paper quality is improved. However, when plastic films are used, new problems that have not conventionally occurred with plain paper arise, such as the generation of static electricity and insufficient adhesion between the coating film and the support. The generation of static electricity is a particularly important problem.If static electricity is generated between the coating process and the calendering process, and if dust or dirt adheres to it, that area will be blanked out during printing, significantly reducing the product image. . In addition, with the recent increase in speed and density of heat-sensitive recording sheets, thermal heads (including their control circuits) have become more highly integrated. Due to the generation of static electricity, problems such as electrostatic damage in electronic devices, paper jams, and poor stockability are becoming more noticeable.

Conventionally, it has been known to use a conductive agent to prevent the generation of static electricity (Japanese Patent Laid-Open No. 60-46294).
However, when a conductive agent is used on a heat-sensitive surface, there are problems such as image fading and background fogging during storage, and the coating solution gelling due to shock.

〔the purpose〕

The purpose of the present invention is to prevent the agglomeration of the coating liquid during production as described above;
The object of the present invention is to provide a heat-sensitive recording material that is free from gelation, liquid blur, etc., prevents the generation of static electricity, has strong paper strength, and has excellent image reliability.

〔composition〕

According to the present invention, there is provided a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer as main components is provided on a support, wherein the support is made of a plastic film, and the heat-sensitive color forming layer has an electrically conductive layer on the heat-sensitive color forming layer. Provided is a heat-sensitive recording material characterized in that a first overcoat layer containing a material and a second overcoat layer containing a film-forming polymeric binder as a main component are provided in that order.

That is, the heat-sensitive recording material of the present invention provides a heat-sensitive coloring layer containing a leuco dye and a color developer as main components on a plastic film support, a first overcoat layer containing a conductive material thereon, and a first overcoat layer containing a conductive material. A second overcoat layer containing a film-forming polymeric binder as the main component is provided on top of this, and because of the above structure, there are no problems such as liquid properties or generation of static electricity during manufacturing. The paper quality is strong and the image reliability is excellent.

Conductive materials (hereinafter referred to as conductive agents) can be roughly divided into:

It is divided into ionic conductivity type and electronic conductivity type. Electronically conductive conductive agents are less dependent on the environment (humidity) and have stable performance as conductive agents, but they have problems such as being often colored or being expensive, so ionically conductive conductive agents are usually used. It is often done.

However, few ion-conducting conductive agents have good compatibility with heat-sensitive materials, and when mixed with heat-sensitive materials, the liquid properties become poor and repellency and streaks are likely to occur during coating. If streaks or repellents occur in the heat-sensitive coloring layer, the image of the product will be significantly degraded, and if they occur in the overcoat layer, the image reliability will be greatly reduced.

Therefore, in conventional heat-sensitive recording materials, only a small amount of the conductive agent can be used due to poor coating properties, and a sufficient antistatic effect cannot be obtained. However, in the present invention, there are two overcoat layers, a conductive agent is used in the first overcoat layer to prevent static electricity, and the second overcoat layer is intended to improve image reliability.

As the conductive agent used in the first overcoat layer of the present invention, either the ion conductive type or the electronic conductive type mentioned above can be used, and specific examples include the following.

As ionic conductive type: Low molecular salts such as sodium chloride, lithium chloride, sodium aluminate, sodium phosphate, calcium chloride, magnesium chloride, potassium formate, and sodium oxalate.

Quaternary ammonium salt, polyethylene polyamine, l-
Hydroxyethyl-2-heptadecyl-glyoxaldine, alkyl phosphate, alkyl sulfate, alkylbenzene sulfonate, alkyl sulfonate,
Polymer electrolytes such as jetanolamide and polyoxyethylene alkyl ether.

As electronic conductivity type: Powders of silver, copper, aluminum, zinc, etc. and their oxides.

Powders such as graphite and carbon black.

Organic semiconductors or polymer semiconductors such as salts of polyacetylene, polyvinylcarbazole, polypyrrole, polythenylene, and tetramethyltetraselenafulvalene.

Other hygroscopic substances include silica, iodized steel, zeolite, etc., but the present invention is not limited to these and may be used in combination as necessary.

The film-forming polymer binder used in the second overcoat layer of the present invention is polyvinyl alcohol.

Examples include polyurethane, hydroxyethyl cellulose, carboxymethyl cellulose, starch and its derivatives, polyvinylidene chloride, styrene/butadiene copolymer, vinyl chloride/vinyl acetate copolymer, styrene/butadiene/acrylic copolymer, and the like.

Note that these binders can also be used in the first overcoat layer.

Various types of plastic films can be used as the support of the present invention, and specific examples include polyester films.

Examples include polyurethane film, polyethylene film, polypropylene film, polyvinylidene chloride film, polystyrene film, nylon film, polycarbonate film, etc., but the present invention is not limited thereto.

However, among these, polyester film is particularly preferred.

The leuco dyes used in the present invention may be applied singly or in a mixture of two or more types. As such leuco dyes, those applied to this type of heat-sensitive material can be arbitrarily applied. For example, triphenyl Leuco compounds of methane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3.3-bis(p-dimethylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis(P- dimethylaminophenyl)-6-dimethylaminophenyl, 3.3-bis(p-dimethylaminophenyl)-6-chlorophthalide.

3.3-bis(p-dibutylaminotunyl)phthalide, 3-cyclohexylamino-6-chlorofluoran.

3-dimethylamino-5,7-dimethylfluorane.

3-N-Methyl-N-isobutyl-6-methyl-7-anilite fluorane.

3-N-Ethyl-N-isoamyl-6-methyl-7-anilite fluorane.

3-diethylamino-7-chlorofluorane.

3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane.

3-(N-p-hly-N-ethylamino)-6-methyl-7-anilitofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-(N-(3'-trifluoran) (methylphenyl)
amino)-6-dinithylaminofluorane.

2-(3,6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran.

3-diethylamino-7-(O-chloroanilino)fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl- 7-(2', 4'-
dimethylanilino) fluorane.

3-(N,N-diethylamino)-5-methyl-7-(
N,N-dibenzylamino) fluorane, benzoylleucomethylene blue.

6'-Chloro-8'-methoxy-benzoindolino-pyrylospirane.

6'-Bromo-3'-methoxy-benzoindolino-pyrylospirane, 3-(2'-hydroxy-41-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide, 3-( 2'-Hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'- Methoxy-5'-methylphenyl)phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'
-methylphenyl)phthalide.

3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane.

3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl) ) Methylaminofluorane.

3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-P-toluidino)-7-(α-phenylethylamino)fluorane, 3-diethylamino-7-(o -methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-)engineered methylethylamino)fluoran.

3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p-n
-butylanilino)fluorane, 3-(N-methyl-N-isopropylamino)-6-methyl-7-anilinofluorane.

3-dibutylamino-6-methyl-7-anilinofluorane, 3,6-bis(dimethylamino)fluorene spiro(9
゜3')-6'-dimethylaminophthalide, 3-(N
-benzyl-N-cyclohexylamino)-5,6-penzo7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-N-ethyl- N-(2-ethokidipropyl)amino-6-methyl-7-anilinofluorane.

3-N-ethyl-N-tetrahydrofurfurylamino-
6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino 4', 5'-benzofluorane, and the like.

In addition, as the color developer used in the present invention, various electron-accepting compounds that cause the leuco dye to undergo catalytic color development are preferably used, such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic acids, and metal salts thereof. applied,
Specific examples include those shown below.

4.4'-isopropylidene bisphenol, 4,4
′ -isopropylidene bis(0-methylphenol)
.

4.4'-Secondary-butylidenebisphenol 4.4'-Isopropylidenebis(2-tertiary-
butylphenol).

4.4'-cyclohexylidene diphenol, 4.4
′ -isopropylidene bis(2-chlorophenol)
.

2.2'-methylenebis(4-methyl-6-tert-butylphenol), 2.2'-methylenebis(4-ethyl-6-tert-butylphenol), 4.4'-butylidenebis(6-tert-butyl-2 - methylphenol).

1.1.3-tris(2-methyl-4-hydroxy-5
-tert-butylphenyl)butane, 1.1.3-tris(2-methyl-4-h-droxy-5-cyclohexylphenyl)butane.

4.4' ~thiobis(6-tert-butyl-2-
methylphenol), 4-4'-diphenol, sulfone.

4-isopropoxy-41-hydroxydiphenylsulfone.

4-benzyloxy-4'-hydroxydiphenyl sulfone, 4.4'-diphenol sulfoxide, isopropyl P-hydroxybenzoate, benzyl P-hydroxybenzoate, benzyl protocatechuate, stearyl gallate.

Lauryl gallate, octyl gallate, 1,7-bis(4-hydroxyphenylthio)-3,5
-Dioxahebutane.

1.5-bis(4-hydroxyphenylthio)-3-oxapentane, 1.3-bis(4-hydroxyphenylthio)-propane, 1.3-bis(4-hydroxyphenylthio)-2-hydroxypropane , N,N'-diphenylthiourea, N,N'-di(m-chlorophenyl)thiourea, salicylanilide.

5-chloro-salicylanilide.

2-Hydroxy-3-naphthoic acid.

2-hydroxy-1-naphthoic acid, 1-hydroxy-2-naphthoic acid, Hydroxynaphthoic acid zinc, aluminum.

Metal salts such as calcium.

Bis-(4-hydroxyphenyl)acetic acid methyl ester.

Bis-(4-hydroxyphenyl)acetic acid benzyl ester, 1,3-bis(4-hydroxycumyl)benzene.

1.4-bis(4-hydroxycumyl)benzene.

2.4'-Diphenolsulfone.

3.3'-Diallyl-4,4'-diphenolsulfone, α,α-bis(4-hydroxyphenyl)-α-methyltoluene.

Antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, etc.

In the present invention, the color developer is generally used in an amount of 1 to 10 parts by weight, preferably 2 to 6 parts by weight, based on the leuco dye type 1 pattern.

In the present invention, various conventional binders can be used as appropriate to bind and support the leuco dye and color developer on the support. Specific examples of such binders include polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, and acrylamide/acrylic. Acid ester copolymer, acrylamide/acrylic ester/methacrylic acid terpolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin In addition to water-soluble polymers such as , casein, polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, and polybutyl methacrylate.

Examples include emulsions such as ethylene/vinyl acetate copolymers, latexes such as styrene/butadiene copolymers, and styrene/butadiene/acrylic copolymers.

In the present invention, in addition to the leuco dye and color developer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, surfactants, thermofusible substances (or lubricants), may be used. ) etc. can be used together. In this case, as a filler.

For example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate,
Examples include fine inorganic powders such as clay, talc, and surface-treated calcium and silica, as well as fine organic powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin. Examples of fusible substances include 1. For example, higher fatty acids or their esters, amides, or metal salts, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, 3.4 -Epoxy-dialkyl hexahydrophthalate, higher ketones, and other thermofusible organic compounds having a melting point of about 50 to 200°C can be mentioned.

In the present invention, the first layer containing a conductive agent on the heat-sensitive coloring layer
In order to provide the overcoat layer, a conductive agent and a binder may be dispersed in water to prepare a first overcoat layer coating solution, and this may be coated on the thermosensitive coloring layer. As the binder in this case, a conventional water-soluble polymer or aqueous polymer emulsion is used, and specific examples thereof include those exemplified in connection with the heat-sensitive coloring layer or the film-forming polymer binder. Examples include those exemplified as .

Further, in the present invention, a second overcoat layer is further provided on the first overcoat layer, and the binder for the first overcoat layer or the film-forming polymer binder for the second overcoat layer is as follows: Those consisting of a water-soluble polymer and a water-resistant agent are also preferably used. In this case, the water-resistant agent is one that reacts with the water-soluble polymer substance by condensation or cross-linking reaction to make it water-resistant, such as formaldehyde, glyoxal, chrome throat bandage, and melamine.

Examples include melamine-formaldehyde resin, polyamide resin, polyamide-epichlorohydrin resin, and the like.

Note that the first and second overcoat layers of the present invention can also contain conventional auxiliary additive components 1, such as fillers, thermofusible substances (lubricants), surfactants, etc., as necessary. Specific examples of the thermofusible substance include those exemplified in connection with the thermosensitive coloring layer.

In the heat-sensitive recording material of the present invention, a heat-sensitive coloring layer coating solution containing the above-mentioned components is applied and dried on the surface of a plastic support, a first overcoat layer coating solution containing a conductive agent is applied thereon and dried, and then It is manufactured by applying and drying a second overcoat layer coating liquid containing a film-forming polymeric binder as a main component. It is often used for PO8 thermal labels, thermal tickets, recorder thermal paper for medical measuring instruments, etc.

〔effect〕

Since the heat-sensitive recording material of the present invention has the above-described structure, it is free from static electricity troubles during manufacture, has strong paper strength, and has excellent image reliability.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. still,
All parts and numbers shown below are by weight.

Example 1 A mixture consisting of the following ingredients was ground in a sand grinder for 2 to 4 minutes.
An Al-(D) solution was prepared in a time-dispersive manner.

(A) Liquid 3- (N-methyl-N-cyclohexyl)amino-6
-Methylanilinofluorane 25.0 parts Polyvinyl alcohol 10% aqueous solution 25.0 parts Water
50.
0 parts [B] Liquid HO-〇-3CH2CI1.0CH20CH,CH,S
-◎-0)1 75.0 parts calcium carbonate
100.0 parts polyvinyl alcohol 10
% aqueous solution 200.0 parts water
, 400, 0 parts (C) Liquid - Zinc stearate 20.0 parts Methyl cellulose 5% aqueous solution 20.0 parts Water
60
．． 0 parts (D) Liquid silica 1.6 parts Water 15
．． A mixture consisting of the following components was stirred with an agitator to prepare a heat-sensitive coloring-free coating solution and an overcoat layer coating solution.

[Thermosensitive coloring layer coating liquid]

(A) liquid 40.0 parts (B) liquid 320.0
Department water
60.0 parts [first overcoat layer coating liquid] CD) liquid 45.0 parts water
10.5 parts [2nd overcoat layer coating liquid] (D) liquid 45.0 parts (C) liquid 0.7 parts Water 1
1.3 parts Next, the obtained heat-sensitive coloring layer coating liquid and the first and second overcoat layer coating liquids were coated on one side of a 100 μm thick polyester film (manufactured by Teijin Ltd.) so that the dry weight of the heat-sensitive coloring layer was 5. , 0g/I8, first overcoat layer is 1.5
After coating and drying, the heat-sensitive recording material of the present invention was obtained so that the Bekk smoothness became 3000-5000 seconds.

Example 2 Example 1 except that the conductive agent polyvinylbenzyltrimethylammonium chloride in the first overcoat layer coating liquid was replaced with a conductive filler (silica oxide particles treated with tin oxide). The heat-sensitive recording material of the present invention was obtained in the same manner as described above.

Example 3 The same procedure as in Example 1 was carried out except that the conductive agent polyvinylbenzyltrimethylammonium chloride in the first overcoat layer coating liquid was replaced with N,N-bis(2-hydroxyethyl)alkylamine. A heat-sensitive recording material of the present invention was obtained.

Comparative Example 1 A comparative heat-sensitive recording material was obtained in the same manner as in Example 1, except that the conductive agent polyvinylbenzyltrimethylammonium chloride in the first overcoat layer coating liquid was omitted.

Comparative Example 2 In Example 1, the first overcoat layer coating liquid was applied and dried to form an overcoat layer with a dry coating weight of 3.5 g/nf, but the second overcoat layer was not provided. A comparative heat-sensitive recording material was obtained in the same manner as in Example 1.

Comparative Example 3 A comparative heat-sensitive recording material was obtained in the same manner as in Example 1, except that high-quality paper with a basis weight of 52 g/nf was used as the support instead of the polyester film.

The heat-sensitive recording material obtained as described above was measured using a thermal inclinometer with a built-in thermal head (manufactured by Toyo Seiki Seisakusho) at a temperature of 70 to 150°C, a crimping time of 1 second, and a crimping pressure of 2 kg/cm.
Printing was carried out under conditions of a# to test the storage stability of the image area and background area. Furthermore, each sample was tested for chargeability and measured for paper strength using a paper analyzer.

The results are shown in Table 1. The density values were measured using a Macbeth densitometer RD-914 model and a W-106 filter.

The test conditions for the test items are as follows.

(1) Electrical strength characteristics i) Charge voltage: When a sample that has been conditioned for more than 5 hours at 20°C ± 2°C and humidity 60% ± 3% is applied with an applied voltage of 2000 V using a paper analyzer. Measure the charging voltage.

if) Half-life time: After measuring the charged voltage, measure the time until the peak voltage is halved when the applied voltage is turned off.

(2) Paper strength i) Tensile strength: Measured in accordance with JIS-P-8113.

ii) Tear strength: Measured in accordance with JIS-P-8116.

(3) Thermal quality i) Plasticizer resistance test: A polyvinyl chloride sheet containing a plasticizer is superimposed on the colored area printed at 150°C.
Apply a load of 100g/aJ.

The concentration is measured after storage at 40° C. for 15 hours under dry conditions.

(2) Oil resistance test: The colored area printed at 150°C is coated with cottonseed oil, and the density is measured after storage at 40°C under dry conditions for 15 hours.

5) Water resistance test: Put 90g of water in a 100cc glass beaker, immerse the colored sample printed at 150°C in it, and measure the density after storage at 20°C for 15 hours.

From Table 1, it can be seen that the heat-sensitive recording material of the present invention is less likely to generate static electricity than the comparative materials, has strong paper quality, and has good image reliability.

Claims (2)

[Claims] (1) A heat-sensitive recording material comprising a heat-sensitive coloring layer containing a leuco dye and a color developer as main components on a support, wherein the support is made of a plastic film and contains a conductive material on the heat-sensitive coloring layer. 1. A heat-sensitive recording material comprising a first overcoat layer and a second overcoat layer containing a film-forming polymeric binder as a main component in that order. (2) The heat-sensitive recording material according to claim 1, wherein the support comprises a polyester film.