JPH04175187A - Thermal recording material - Google Patents

Abstract

PURPOSE:To eliminate a hickey, a failure in uniformity, a discontinuous line, and the like by a method wherein a substrate forming a thermal recording material is calendered to be 500sec or more in Oken smoothness specified in J.TAPPI No.5 on the coated surface of the substrate. CONSTITUTION:As a substrate, synthetic paper having a double layer structure is used. On one surface of said substrate, a thermal color-forming layer is provided, which contains a colorless or light-colored electron donative leuco dye, an organic acid substance causing said leuco dye to produce a color under heat, and an adhesive as main components. An over coat layer is further provided on said thermal color-forming layer, as required. In this manner, a thermal recording material is produced. Furthermore, it is required that the substrate should be calendered to be 500 sec or more in Oken smoothness specified in J.TAPPI No.5 on the coated surface of the substrate. The synthetic paper is calendered by a super calender, a gloss calender, or the like to be 500 sec or more in Oken smoothness (in accordance with J.TAPPI No.5). In this manner, unfavorable projections can be smoothed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat-sensitive recording medium.
The present invention relates to a thermal recording medium suitable for use in a thermal plotter that outputs drawings created in a []esign) system, and a thermal image printer that outputs CRT images for medical measurement as hard copies.

[Conventional technology]

Thermosensitive recording materials generally consist of a support made of paper, synthetic paper, or plastic film, on one side of which is a colorless or light-colored color-forming substance such as an electron-donating leuco dye and an electron-accepting phenolic compound. A heat-sensitive coloring layer containing an organic acidic color developer and an adhesive as main components is provided, and a color-forming recorded image can be obtained by reacting these color-forming dyes and the color developer with thermal energy. It is possible.

Such heat-sensitive recording media has the advantages of compact and inexpensive recording devices and easy maintenance, so it can be used for computer output, facsimiles, automatic ticket vending machines, scientific measuring machines, and CAD. It is widely used in applications such as printers, plotters, and printers for CRT medical measurement.

Among these are CRT image printers for medical measurement, which require not only water resistance and tensile strength, but also uniformity and high resolution of recorded images, and CAD, which requires dimensional stability and fine line recording.
The plotter uses thermal paper with a multi-layered synthetic paper as a support.

However, commercially available synthetic paper with a multilayer structure has an uneven surface in order to improve printability and writability, which are the essential properties of synthetic paper, and some of the protrusions are suitable for thermal recording materials. There is a protrusion with an inappropriate height (5 μm or more) as a support.

When images are recorded on thermal recording paper using such a support, white spots occur in the intermediate layer and solid recording areas, and
There were problems such as a decrease in uniformity and lines breaking when thin line recording was performed.

[Problem to be solved by the invention]

The present invention attempts to improve problems such as white spots, poor uniformity, and line breakage caused by protrusions on the surface of synthetic paper having a multilayer structure.

[Means to solve the problem]

The present invention uses synthetic paper with a multilayer structure as a support, and one side of the support contains a colorless or light-colored electron-donating leuco dye, an organic acid substance that causes the leuco dye to develop color when heated, and an adhesive as main components. In a heat-sensitive recording material, which is provided with a heat-sensitive coloring layer containing a fluorine and an overcoat layer, if necessary, an overcoat layer is provided on the heat-sensitive coloring layer, and J on the coated side of the support is calendered.

The Oken type smoothness specified in TAPPI No. 5 is 5.
By setting the time to 00 seconds or more, problems such as missing whites, poor uniformity, and line breaks can be improved.

The synthetic paper having a multilayer structure used in the present invention is made of one or more resins selected from polypropylene, polystyrene, high-density polyethylene, medium-density polyethylene, low-density polyethylene, and ethylene-vinyl acetate copolymer. It is a synthetic paper made by heating and kneading calcium carbonate and calcined clay, extruding it from Gui to form a film, and then laminating 3 to 5 layers. , TPO (semi-transparent type), KPK (semi-transparent type), 5GG (semi-transparent type), FPG (opaque type), WFP (opaque thick type), WCF (opaque type) and other grades with a thickness of 60 μm. ~500
μm can be used.

These synthetic papers have 30 or more protrusions per square meter with a height of 5 μm or more on the surface, which causes white spots, poor uniformity, and line breakage when a heat-sensitive coloring layer is coated and recorded.

These synthetic papers are treated with a calender such as a super calender, a gloss calender, a machine calender, etc. by heating the calender roll at 40°C to 80°C as necessary, and are evaluated for Oken type smoothness (J).

By setting TAPPI, N [based on 15] for 500 seconds or more, preferably 600 seconds or more, the protrusion can be crushed.

When a thermosensitive layer is applied to calendered synthetic paper and recorded, white spots, uniformity, and line breakage are improved, and records of good quality can be obtained.

After the calender treatment, the dimensional stability, water resistance, writing strength, and adhesion of the coating layer of the Yubo were comparable to those without the treatment.

The thermosensitive coloring layer of the present invention contains as main components a colorless or light-colored electron-donating leuco dye, an organic acidic substance that causes the leuco dye to develop color when heated, and an adhesive.
Examples of leuco dyes include 2.2bis(4-[6'
-(N-cyclohexyl-N-methylamino)-3'
-Methylspiro[phthalide-3,9'-xanthine]
-2'-ylamido]phenyl)propane, 3-diethylamine-6-methyl-7-anilinofluorane, 3-
piperidino-6-methyl-7-anilinofluorane, 3
-(N-methylN-cyclohexylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-7
-chloroanilinofluorane, 3-[N-ethyl-N-
(p-Methylphenyl)aminoco-6-methyl-fuanilitufluorane, 3-diethylamino-7-(metatrifluoromethyl)anilinofluorane, 3-[N-ethyl-N-tetrahydrofurfuryl]amino-6 -Methyl-7-aniritefluoran, 3-[N-ethyl-isopentylcoamino-6-methyl-7-aniritefluorane, 3-[N,N dibutylroamino-6-methyl-7-
At least one kind or a mixture of two or more kinds of fluoran dyes such as anilifluorane can be used.

The organic acidic substance used in the present invention has a color-developing action capable of reacting with a leuco dye under heating to develop a color. Such a color developer liquefies or vaporizes at room temperature or higher, preferably 70° C. or higher, and reacts with the leuco dye to develop color.

As the color developer that can be used in the present invention, for example, 4.4'-
Isopropylidene diphenol (bisphenol A),
1.4'-isopropylidene bis(2-40phenol), 4.4'-isopropylidene bis(2-methylphenol), 4.4'-isopropylidene bis(2,
6-tert-butylphenol)% 4. 4'
-5ec-butylidene diphenol, 4.4'-chlorohexylidene diphenol, 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, naphthol, β-naphthol, methyl-4-hydroxybenzoate, 4- Hydroxy-acetophenone, salicylic acid anilide, novolac type phenolic resin, halogenated novolac type phenolic resin, 4
．． 4'-thiobis(3-methyl-6-tert-butylphenol), propyl p-hydroxybenzoate, p-
Aliphatic carboxylic acids such as isopropyl hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, methylbenzyl p-hydroxybenzoate, oxalic acid, maleic acid, tartaric acid, citric acid, succinic acid, stearic acid, Benzoic acid, p-tert-butylbenzoic acid, phthalic acid, gallic acid, salicylic acid, 3-isopropylsalicylic acid, 3.5-di-α-methylbenzylsalicylic acid, bis(4-hydroxyphenyl) sulfide, 1.7-di (4-1)'roxyphenylthio)-3,
5-dioxaheptane, p-nitrobenzoic acid, and these organic color developers such as zinc, magnesium, aluminum,
Salts with polyvalent metals such as calcium, titanium, manganese, tin, and nickel, 4,4'-dihydroxydiphenylsulfone, 2,4'-dihydroxydiphenylsulfone,
3.3'-dihydroxydiphenylsulfone, 3.3
'-Diamino=4,4'-dihydroxy-diphenylsulfone,3,3'-diallyl-4,4'-dihydroxy-diphenylsulfone,3,3'-dichloro-4,
4'-dihydroxydiphenylsulfone, 4-hydroxy-diphenylsulfone, 4-hydroxy-4'-isopropyldiphenylsulfone, 4-hydroxy-4'-
Isopropyloxydiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 2.4
-dihydroxy-diphenylsulfone, 2,4-dihydroxy-4'-methyldiphenylsulfone, and 3,
One type or a mixture of two or more types selected from 4-dihydroxyphenyl-p-)U sulfone and the like can be used.

The color developer is usually mixed and used in a ratio of 1 to 6 parts by weight, preferably 1.5 to 4 parts by weight, per 1 part by weight of the leuco dye.

In the present invention, the adhesives contained in the heat-sensitive coloring layer include those conventionally known as adhesives for heat-sensitive coloring layers.
All are usable. However, when mixed with each dispersion of the leuco dye and color developer, the mixture may develop color or
It is preferable that the heat-sensitive recording layer does not aggregate or become highly viscous, and the formed heat-sensitive recording layer film is required to be tough and to have no desensitizing effect.

Examples of water-soluble adhesives include polyvinyl alcohol, modified starch, gum arabic, gelatin, methylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, polyvinylpyrrolidone, polyacrylate, polyacrylamide, styrene-maleic anhydride copolymer, and methyl vinyl ether. Maleic anhydride copolymer, isopropylene-maleic anhydride copolymer, water-dispersible adhesives include styrene-butadiene latex, vinyl acetate-acrylic acid ester copolymer emulsion, polyurethane emulsion, polyvinyl chloride emulsion, Polyvinylidene chloride emulsion, methacrylic ester copolymer emulsion, acrylic ester copolymer emulsion, etc. can be used.

In order to strengthen the water resistance of the coating film, a water-soluble and/or water-dispersible polymer substance containing a reactive group, such as an acetoacetyl group, a carboxyl group, or an amide, is combined with a crosslinking agent. It is preferable to use

Examples of crosslinking agents for water-soluble polymer substances include glyoxal,
Dialdehyde compounds such as polyaldehyde, polyamine compounds such as polyethyleneimine, epoxy compounds,
Polyamide resins, diglycidyl compounds such as glycerin diglycidyl ether, dimethylol urea compounds, and inorganic compounds such as ammonium persulfate, ferric chloride, and magnesium chloride can be used.

The heat-sensitive coloring layer may contain a pigment, particularly a white pigment, if necessary. Examples of such pigments include calcium carbonate, magnesium carbonate, kaolin, clay,
Talc, calcined clay, silica, diatomaceous earth, synthetic aluminum silicate, zinc oxide, titanium oxide, aluminum hydroxide, barium sulfate, surface-treated inorganic fine powders such as calcium carbonate and silica, and urea-formalin resin. , styrene-methacrylic acid copolymer, polystyrene resin, and other organic resin fine powders.

If necessary, auxiliary additive components conventionally used in heat-sensitive recording materials, such as dispersants, surfactants, thermofusible substances, etc., may be added to the heat-sensitive coloring layer. Examples of thermofusible substances include fatty acid amides such as stearic acid amide, stearic acid ethylene bisamide, oleic acid amide, palmitylic acid amide, coconut fatty acid amide, behenic acid amide, zinc stearate, calcium stearate, polyethylene wax, Waxes (or lubricants) such as carnauba wax, paraffin wax, and ester wax, dimethyl terephthalate, dibutyl terephthalate, dibenzyl terephthalate, dibutyl isophthalate, phenyl 1-hydroxynaphthoic acid, 1゜2-silica (3-methylphenoxy)ethane, lI2-diphenoxyethane, 1-
Phenoxy-2-(4-methylphenoxy)ethane, diphenyl carbonate, p-benzylbiphenyl, 2.2'-
Methylenebis(4-methyl-6-t-butylphenol), 4.4'-butylidenebis(6-t-butyl-3
-methylphenol), 1.1°3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 2.2'-methylenebis(4-ethyl-6-t-butylphenol), 2. 4-di-t-butyl-3-methylphenol, 4,4'-thiobis(3-methyl-6
Hindered phenols such as -t-butylphenol), 2-(2'-hydroxy-5'-methylphenyl)
- Sensitizers such as benzotriazole and 2-hydroxy-4-benzyloxybenzophenone, antioxidants,
Examples include ultraviolet absorbers.

Generally, it is preferable that the thermofusible substance is contained in the thermosensitive coloring layer in a proportion of 4 parts by weight or less per 1 part by weight of the color developer.

The heat-sensitive coloring layer contains the above-mentioned leuco dye, organic acid substance, and adhesive as main components, and optionally contains a cross-linking agent, a white pigment, a dispersant, a surfactant, and a heat-decomposable substance. It can be obtained by coating one side of

As the coating method, methods conventionally used by those skilled in the art, such as a Meyer bar method, an air knife method, a blade method, a reverse roll method, and a slit die method, can be used.

The coating amount when dry is 2 to 13 g/m", preferably 3 to 1
0g/m''.

In addition, the recording stability of the thermosensitive recording medium, for example, the recorded matter is 50%
Because it does not reduce the recording density even if it is stored in high temperature conditions of 80% RH to 90% RH, or comes into contact with plasticizers contained in erasers, PVC films, etc., or is water resistant. If necessary, an overcoat layer can be provided on the heat-sensitive coloring layer to impart glossiness and writability.

The overcoat layer contains a water-soluble resin or a water-dispersible resin and, if necessary, a white pigment, a crosslinking agent, a dispersant, and a surfactant, which are selected from those used in the heat-sensitive coloring layer. can be used.

As the coating method for the overcoat layer, the same method used for coating the heat-sensitive coloring layer can be used. Coating amount after drying is 0.5 g/m" to 10 g/m", preferably Ig/m
It is adjusted to 2 to 8 g/m2.

If the coating amount is less than 0.5 g/m 2 , the effect of providing the overcoat layer cannot be obtained, and if it exceeds 10 g/m 2 , there is a problem of lowering the coloring sensitivity.

Furthermore, if the effect is insufficient after applying the overcoat layer once, it is also possible to apply the overcoat layer in two separate times. In that case as well, the total coating amount is preferably 10 g/m2 or less.

Furthermore, the effect can be enhanced by changing the paint composition for the second coating from that for the first coating.

For example, pinholes in the paint film that cannot be completely eliminated with one coat can be covered with a second coat, improving the barrier properties of the entire overcoat layer and improving storage stability. The barrier property is maintained during coating, and the second coating is a coating with a high pigment content to give printability and writability, or the second coating is a solvent-based coating, UV-curable coating, or EB curing. By using it as a mold paint, an overcoat layer with high gloss can be obtained.

Solvent-based paints include, for example, vinyl acetate resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin, acrylic ester resin, butyral resin, polyester resin, nitrocellulose resin, styrene resin, styrene-acrylic copolymer resin, etc. It can be prepared by blending a crosslinking agent having an isocyanate group, an epoxy group, an ethyleneimine group, an alkoxymethyl group, a hydrazine group, an aziridine group, etc., and if necessary, a pigment, a lubricant, etc.

UV-curable paints are made of photopolymerizable monomers such as various ethylene dielectrics, prepolymers or polymers such as unsaturated polyester, epoxy, acrylic, various polyesters, etc.
It can be prepared by blending a white pigment, a lubricant, etc. with an ultraviolet curing resin consisting of a photopolymerization initiator and a photopolymerization initiator, if necessary.

EB curable paints are made of aliphatic alicyclic, araliphatic, di- to hexavalent polyhydric alcohols, and poly(meth)acrylates and poly(meth)acrylates of polyhydric alcohols with added polyalkylene glycols or alkylene oxides. Acryloyloxyalkyl phosphate ester, polyester poly(meth)acrylate, epoxy poly(meth)acrylate, polyurethane poly(meth)acrylate, polyamide poly(meth)acrylate, polysiloxane poly(meth)acrylate, in side chains and/or terminals Vinyl or diene prepolymers having (meth)acryloyloxy groups, carboxyl group-containing polymers represented by ethylenically unsaturated mono- or polycarboxylic acids, and their alkali metal salts, ammonium salts, amine salts, etc. It can be prepared by blending a prepolymer or monomer that can be cured by electron beams, such as a carboxylic acid group-containing monomer, with a white pigment, a lubricant, etc., if necessary.

For UV-curable paints and EB-curable paints, the coating amount is 0.1 g/m'' to 10 g on the first overcoat layer.
/ m2 preferably 0.5 g/m” to 8 g/m2
It is coated so that

〔Example〕

EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the scope of the present invention is of course not limited to these. In each example, "part" indicates "part by weight J."

Examples 1 to 3 Commercially available semi-transparent synthetic paper (TP (made by -75° egg oil-treated synthetic paper) was smoothed with a super calender,
Oken style Bekk smoothness of one side is 650 seconds (Example 1) 1,
000 seconds (Example 2) and 2.100 seconds (Example 3). The heat-sensitive coloring layer paint prepared by the following procedure was applied on the surface to be measured for smoothness so that the coated amount after drying was 5.5g/m2, and the coloring layer was smoothed using a super calender. A heat-sensitive recording material was obtained using the Ohken Bekk smoothness of 1,500 seconds.

Solution A (thermochromic dye dispersion) 7-anirite fluorane 5 parts 10% methyl vinyl ether-maleic anhydride copolymer aqueous solution 5 parts water
8 parts Solution B (developer dispersant) 2・4-';b)' o 4-'-';' 7
”: Jl, 30 parts sulfone 10% methyl vinyl ether-maleic anhydride copolymer aqueous solution 30 parts water
22 parts A liquid and B liquid were separately dispersed and pulverized using an Ultra Visco Mill, and the average particle size was adjusted to 1 μm or less.

Solution A 15 parts Solution B 38 parts 60% calcium carbonate slurry 33 parts 10% aqueous polyvinyl alcohol solution 50 parts 30% aqueous zinc stearate dispersion 7 parts 20% aqueous stearamide dispersion 3 parts water
20 parts were mixed to form a heat-sensitive coloring paint.

Example 4 A commercially available opaque type synthetic paper (manufactured by FPG 95° Egg Oil Synthetic Paper ■) was smoothed using a gloss calender, and the Oken type smoothness of one side was set to 2.000 seconds. The amount of coating after drying of the heat-sensitive coloring layer paint used in Example 1 on the surface to be measured for smoothness was 6.
．． It was coated so that it was Og/m'.

On the thermosensitive coloring layer, 60% clay aqueous dispersion 15 parts 10% glyoxal 10 parts water
After coating the overcoat layer consisting of 29 parts so that the coating weight after drying is 3.0 g/m', smoothing treatment is performed using a super calender, and the Oken type smoothness of the overcoat layer is reduced to 1. .200
Seconds.

Example 5 A commercially available opaque type synthetic paper (CFG-80° Egg Oil Chemical Synthetic Paper ■) was smoothed using a super calender, and the Oken type smoothness on one side was set to 1.200 seconds.

The heat-sensitive coloring layer paint used in Example 1 was applied to the smoothness measurement surface so that the coating amount after drying was 6.5 g/m2, and the overcoat layer used in Example 4 was applied on the heat-sensitive coloring layer. was applied so that the coating amount after drying was 3.0 g/m2.

Smoothing treatment was performed using a super calender, and the Oken type smoothness of the overcoat layer was set to 2.000 seconds. Furthermore, a paint consisting of 97 parts of polyester acrylate prepolymer (M-8030, manufactured by Toagosei ■), 2 parts of calcium carbonate, and 1 part of calcium stearate was applied on the overcoat layer.
It was coated at 1.0 g/m2 and irradiated with an electron beam of 3 Mrad using an electron beam irradiation device to obtain a heat-sensitive recording material.

Comparative Examples 1 to 3 The amount of heat-sensitive coloring layer paint used in Example 1 after drying was applied to one side of the synthetic paper that was not subjected to the smoothing treatment used in Examples 1, 4, and 5. After coating at a density of 5.5 g/m', smoothing treatment was performed using a super calender to obtain a coloring layer with a smoothness of 1.500 seconds to obtain a heat-sensitive recording material.

The results of printing the thermal recording bodies produced in Examples and Comparative Examples using a commercially available thermal plotter (8 dots/mm) are shown in the table below.
Shown in 1.

The heat-sensitive recording materials obtained in Examples 1 to 5 had no line breaks or white spots, and records with good uniformity were obtained, whereas the heat-sensitive recording materials obtained in Comparative Examples 1 to 3 had lines. It could not be used as plotter paper because it was cut and had white spots.

Table 1 Smoothness: Oken type smoothness Line breaks: Number of line breaks t per 1 m2 when one dot straight line is recorded at 1 mm intervals White missing parts: Number of white missing parts per 1 m2 when solid recording is performed ○: 10 pieces/m2 or less, △: 11 pieces/m2~3
0 pieces/m2, Records can be obtained.

Patent applicant: Oji Paper Co., Ltd.

Claims (1)

[Claims] A synthetic paper with a multilayer structure is used as a support, and one side of the support contains a colorless or light-colored electron-donating leuco dye, an organic acidic substance that causes the leuco dye to develop color when heated, and an adhesive as main components. In a heat-sensitive recording material provided with a heat-sensitive color-forming layer and further provided with an overcoat layer on the heat-sensitive color-forming layer if necessary, the J.I. TAPPI No. 5. A heat-sensitive recording material characterized in that the Oken type smoothness specified in Item 5 is 500 seconds or more.