JPH04219277A - Thermal recording material - Google Patents

Abstract

PURPOSE:To improve missing dots, uniformity inferiority and line cutting by setting the number of protruding parts whose height is a predetermined value or more of the inorg. fine powder protruding from the flat surface of the surface layer of the support of a thermal recording material per a unit area to a predetermined number or less. CONSTITUTION:A thermal recording material is formed by providing a thermal color forming layer to the single surface of a support 1 composed of synthetic paper having a double-layer structure and further providing an overcoat layer thereto if necessary. The support pref. consists of a surface layer C composed of a thermoplastic resin film containing 0-3wt.% of an inorg. fine powder, a paper-like layer B composed of the film containing 8-65wt.% of the inorg. fine powder and a base material layer A composed of the film containing 0-5wt.% of the inorg. fine powder. Herein, the number of the protruding parts 8 whose apexes 9 have height of 5mum or more of the powder 6 protruding from the flat surface of the surface layer C is set to 50 or less per 0.1m<2> of a base material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat-sensitive recording medium, and more specifically, CAD (Computer Aided Design).
The present invention relates to a thermal recording medium suitable for use in a thermal plotter that outputs drawings created in a CRT sign 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. can. Such heat-sensitive recording media has the advantage that the recording device is compact and inexpensive, and it is easy to maintain, so it can be used for computer output, facsimiles, automatic ticket vending machines, scientific measuring machines, etc. CAD printer,
It is widely used as a plotter or a printer for CRT medical measurement.

In addition to water resistance and tensile strength, it is also used in CRT medical measurement printers that require uniformity and high resolution of recorded images, and in CAD plotters that require dimensional stability and fine line recording. In this case, thermal paper with a support made of synthetic paper having a multilayer structure is used.

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 halftone areas and solid recording areas, resulting in problems such as decreased uniformity and line breaks when recording thin lines. Ta.

[Problem to be solved by the invention]

The present invention aims to improve problems such as white spots, poor uniformity, and line breakage caused by protrusions on the surface of the synthetic paper in a heat-sensitive recording material using a synthetic paper having a multilayer structure as a support.

[Means to solve the problem]

The present invention provides a heat-sensitive recording material comprising a synthetic paper having a multilayer structure as a support, a heat-sensitive coloring layer provided on one side of the support, and an overcoat layer provided on the heat-sensitive coloring layer as necessary. This book was developed based on the knowledge that the height and number of protrusions protruding from the base material surface can be changed by selecting the average particle size and content of the inorganic fine powder contained in each layer of synthetic paper with a multilayer structure. Completed the invention.

That is, the present invention provides a heat-sensitive recording having a structure in which a heat-sensitive coloring layer 2 and an overcoat layer 3 provided as necessary are sequentially provided on one side of a support 1 made of synthetic paper having a multilayer structure, as shown in FIG. In body 4, the support has a surface layer made of a thermoplastic resin film containing 0 to 3% by weight of inorganic fine powder, and a paper-like layer made of a thermoplastic resin film containing 8 to 65% by weight of inorganic fine powder. A thermosensitive recording film having a multi-layer structure comprising: a film having a multi-layer structure, wherein the number of protrusions having a height of 5 μm or more protruding from the flat surface of the surface layer is 50 or less per 0.1 m2 of the base material. It's about the body.

The support in the heat-sensitive recording material of the present invention may preferably include a base layer in addition to the surface layer and the paper-like layer.

FIG. 2 shows an example of a thermosensitive recording medium. Support 1 is paper-like layer B
, a surface layer C and a base layer A.

Examples of thermoplastic resins constituting each layer of the support include polyolefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, poly(4-methylpentene-1), polystyrene, polyamide, and polyethylene terephthalate. , partial hydrolysates of ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers and their salts, vinylidene chloride copolymers such as vinyl chloride-vinylidene chloride copolymers, and mixtures thereof.

Inorganic fine powders to be blended into the thermoplastic resin include calcium carbonate, calcined clay, diatomaceous earth, talc, titanium oxide, and calcium carbonate with an average particle size of 20 μm or less for the base material layer and paper layer.
Barium sulfate, aluminum sulfate, silica, etc. are used, and for the surface layer, calcium carbonate, titanium oxide, barium sulfate, etc. are used.

Next, each layer will be explained in detail.

(1) Paper-like layer The paper-like layer contains (a) 35 to 92% by weight of polypropylene;
(b) One or more thermoplastic resins selected from polystyrene, high-density polyethylene, medium-density polyethylene, low-density polyethylene, and ethylene/vinyl acetate copolymer.
A film obtained by uniaxially stretching a composition consisting of 30% by weight and (c) 8 to 65% by weight of an inorganic fine powder is used.

Polystyrene, high-density polyethylene, medium-density polyethylene, low-density polyethylene, and ethylene/vinyl acetate copolymers are used to improve stretchability, and polystyrene and high-density polyethylene improve the foldability of synthetic paper. This is because it has an effect. However, since the contribution of the base material layer, which is a biaxially stretched film, is greater than that of the paper-like layer, there is no need to actively incorporate it.

As the inorganic fine powder, calcium carbonate, calcined clay, diatomaceous earth, talc, titanium oxide, barium sulfate, aluminum sulfate, silica, etc. with an average particle size of 20 μm or less are used. These contribute to opacity, whitening, and paper-like formation of the paper-like layer. In FIG. 2, the inorganic fine powder contained in the paper-like layer is indicated by 5. The inorganic fine powder 6 protruding from the paper-like layer B to the surface layer C serves as an anchor, and the surface layer C
, enhances the adhesive strength with the base material layer A. The upper left part of FIG. 2 shows agglomerated inorganic fine powder, and the upper right part shows giant particles. Of these, the portions of the surface layer C that protrude from the flat surface 10 are referred to as protrusions 8. In order to increase the opacity of the synthetic paper, the content of fine inorganic powder in the paper-like layer is 8% by weight or more. However, since mechanical strength (compressive strength, tensile strength, etc.) as a paper-like layer is required, the upper limit of the inorganic fine powder should be 65% by weight.

Preferably, the composition ratio of the paper-like layer is as follows.

(a) Polypropylene 45-65% by weight (b) Resin such as polyethylene 0-5% by weight (c) Fine inorganic powder
35 to 55% by weight This paper-like layer is provided on one or both sides of the base layer, if used.

(2) Surface layer The surface layer consists of (a) 40 to 60% by weight polypropylene, (b)
) 60 to 40% by weight of high-density polyethylene; and (c) 0 to 3% by weight of inorganic fine powder. The film is uniaxially stretched. Polyethylene has a density of 0.940
A high density material of -0.970 g/cm3 is preferred.

High-density polyethylene makes transparent polypropylene opaque without using fine inorganic powder, reduces surface gloss and smoothness, makes it easier to write on synthetic paper with oil-based pens, etc., and makes written characters readable. It exhibits a facilitating effect and is used in a proportion of 40 to 60% by weight.

In addition, when the surface layer has a thin wall thickness of 0.5 to 10 microns, the surface layer may be made of polypropylene alone.

It is preferable not to include the inorganic fine powder 6 in the surface layer C from the viewpoint of preventing line breakage and white spots. However, in order to improve the adhesion with the heat-sensitive coloring layer and the opacity of the support, it can be added as necessary. in this case,
The amount added is at most 3% by weight or less. The average particle size of this inorganic fine powder is preferably 3 μm or less in order to limit the height of protrusions and prevent white spots. As this inorganic fine powder, calcium carbonate, titanium oxide, barium sulfate, etc. can be used.

In the present invention, the protrusions 8 which protrude from the flat surface of the surface layer and have a height h of 5 μm or more are formed on the base material by 0.1 m2.
An important feature is that the number of pieces per hit is 50 or less. The height of the protrusion is indicated by h in Figure 2, but here, the problem is particularly when the height of the protrusion is 5 μm or more, because the diameter of the existing fine inorganic powder is 3 μm or less. This is because particles may aggregate with each other and become giant particles with a particle size of 5 μm or more, and such particles may be included.

If the number of protrusions with a height of 5 μm or more that protrudes from the flat surface of the surface layer exceeds 50 per 0.1 m 2 of the base material, line breakage and white spots may occur, which is not preferable.

(3) Base material layer The base material layer includes (a) 50-95% by weight of polypropylene;
(b) 0 to 30% by weight of one or more thermoplastic resins selected from high density polyethylene, medium density polyethylene, low density polyethylene, and ethylene/vinyl acetate copolymer;
(c) A film obtained by biaxially stretching a composition consisting of 50 to 5% by weight of inorganic fine powder is used. Here, low-density polyethylene, medium-density polyethylene, high-density polyethylene, and ethylene/vinyl acetate copolymer are used to facilitate stretching of the synthetic paper and to strengthen the adhesion of the paper-like layer.

As described above, these polyethylenes and the like contribute to improving stretchability and impact resistance, but since excessive addition leads to a decrease in the bending strength of the synthetic paper, the upper limit should be 30% by weight or less. The inorganic fine powder 5 can be the same as that used for the paper-like layer. As shown by 7 in FIG. 2, many fine pores are created inside the base layer film by stretching,
It is used to make synthetic paper lightweight, to make the base layer opaque, and to make it easier to stretch.

The upper limit of the amount of inorganic fine powder used is 50% by weight. As the amount of inorganic fine powder increases, the number of pores inside the film increases, and although synthetic paper can be made lighter and more opaque over a wide range, its tensile strength decreases.

Preferably, the composition of the base layer is as follows.

(a) Polypropylene 60-85% by weight (b) Resin such as the aforementioned polyethylene 0-8% by weight (c) Fine inorganic powder 15-40% by weight Next, the thickness of each layer of the support will be explained.

The thickness of the synthetic paper having a multilayer structure is suitably 40 to 800 μm, preferably 60 to 300 μm. The base layer A accounts for 40% or more of the thickness of the synthetic paper.

The thickness of each of the surface layer C and the back layer C is 0.5 to 10 μm. If the thickness is less than 0.5 μm, the inorganic fine powder protruding from the surface of the paper-like layer B may also protrude from this surface layer C and may fall off, so that the effect of preventing line breaks and white spots cannot be expected. As mentioned above, the particle size of the inorganic fine powder in the paper-like layer is usually 3.
It is less than μm, preferably 0.05 to 1.8 μm. Furthermore, if the thickness of the surface layer C exceeds 10 μm, the rough surface effect of the paper-like layer B and the appearance of the paper-like layer will be shaded by the surface layer, and the surface layer will have high gloss and improved smoothness, making it look like paper. Move away from the texture.

The paper-like layer B has a thickness of at least 8 μm or more, preferably 20 to 100 μm, in order to shade the base layer A.

The pores 7 present in the synthetic paper have a porosity of 15 to 65% defined by the following formula.

The stretching ratio is 4 to 10 times in the longitudinal direction and 4 to 12 times in the transverse direction, and the stretching temperature is 140 to 158°C in the longitudinal direction, and a temperature higher than the melting point of polypropylene (163 to 168°C) in the transverse direction.

ρ0: Film density before stretching ρ1: Film density after stretching The synthetic paper support of the present invention can be produced by, for example, extruding the base layer composition into a sheet and stretching it in one direction at a temperature lower than the melting point of polypropylene. A paper-like layer is formed by melt-laminating a co-extruded paper-like layer B composition and a surface layer C composition on both sides of the obtained base material layer A consisting of a uniaxially oriented film. It can be obtained by laminating the polypropylene so that they are in contact with each other, and then stretching the laminated film in a direction perpendicular to the stretching direction at a temperature higher than the melting point of polypropylene.

In addition, a film obtained by melt-laminating a coextruded paper-like layer B composition and a surface layer C composition on one side of a base material layer A film uniaxially oriented in the longitudinal direction. A multilayer synthetic paper obtained by laminating the molten film of the paper-like layer B composition on the other side of the base layer A using another extruder, and stretching the obtained laminate in the transverse direction. It may be.

Since the base layer contains fine inorganic powder, there are many fine pores inside the film of the base layer.

The base material layer of the uniaxially stretched film of this synthetic paper contributes to increasing the strength of the synthetic paper. Moreover, the paper-like layer film exhibits a paper-like texture. If the paper-like layer is a biaxially stretched film, it will have a pearlescent luster, which is far from a paper-like texture. Therefore, by using a uniaxially stretched film as the paper-like layer, this paper-like layer shadows the base material layer and gives the synthetic paper a paper-like feel.

The surface layer covers the paper-like layer containing inorganic powder, prevents the fine inorganic powder from falling off, and has a rough surface that allows writing.

The synthetic paper used as the support can be subjected to corona discharge treatment on the front and back layers, if necessary, to improve printability.

The surface layer side of this synthetic paper can be subjected to gravure printing, screen printing, and flexographic printing, and can also be written on with an oil-based pen. It can also be written on with a pencil. Note that when the back side of this synthetic paper does not have a surface layer and is a paper-like layer, not only the above printing but also offset multicolor printing is possible.

Furthermore, pencil writing properties are also better than when the back side has a surface layer.

The heat-sensitive recording material of the present invention has a structure in which a heat-sensitive coloring layer and, if necessary, an overcoat layer are sequentially provided on the support described in detail above.

The thermosensitive coloring layer of the present invention, a colorless or light-colored electron-donating leuco dye, a leuco dye type that contains an adhesive as a main component and an organic acidic substance that causes the leuco dye to develop color when heated, and a leuco dye type that contains an adhesive as a main component, There is a diazo type that generates an environment and couples with a diazonium salt in a weakly basic environment to form a dye.

Leuco dye-type heat-sensitive coloring layers have poor resistance to heat, humidity, light, plasticizers, oils, etc., but diazo-type heat-sensitive coloring layers are resistant to these things, and even after recording, they can be irradiated with an ultraviolet lamp, etc., without any reaction. When the diazonium salt is decomposed, it becomes a fixable heat-sensitive recording medium that cannot be used for additional recording.

Among the leuco dye types, for example, 2,2bis{4-[6'-(N-cyclohexyl-N
-methylamino)-3'-methylspiro[phthalide-3
,9'-xanthene]-2'-ylamido]phenyl}
Propane, 3-diethylamino-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)amino]
-6-Methyl-7-anilinofluorane, 3-diethylamino-7-(metatrifluoromethyl)anilinofluorane, 3-[N-ethyl-N-tetrahydrofurfuryl]amino-6-methyl-7- Anilinofluorane, 3
-[N-ethyl-isopentyl]amino-6-methyl-
At least one type or a mixture of two or more types of fluoran dyes such as 7-anilinofluorane and 3-[N,N dibutyl]amino-6-methyl-7-anilinofluorane can be used.

The organic acidic substance has a color-developing effect that allows it to react with the 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.

Color developers that can be used in the present invention include, for example, 4,4'-isopropylidene diphenol (bisphenol A), 4,4
'-isopropylidene bis(2-chlorophenol),
4,4'-isopropylidene bis(2-methylphenol)4,4'-isopropylidene bis(2,6-ter
t-butylphenol), 4,4'-sec-butylidene diphenol, 4,4'-cyclohexylidene 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, isopropyl p-hydroxybenzoate, butyl p-hydroxybenzoate, p-
Benzyl hydroxybenzoate, methylbenzyl p-hydroxybenzoate, oxalic acid, maleic acid, tartaric acid,
Fatty acid carboxylic acids such as citric acid, succinic acid, and 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-hydroxyphenylthio)-3,5-dioxaheptane, p-nitrobenzoic acid, and combinations of these organic color developers and polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel. salt, 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- One type or a mixture of two or more types selected from 4'-methyldiphenylsulfone, 3,4-dihydroxyphenyl-p-trisulfone, etc. can be used.

Diazonium salt type compounds include, for example, para-diazo N,N-dimethylaniline chloride zinc chloride double salt, para-diazo N,N-diethylaniline chloride zinc chloride double salt, and para-diazo N-ethyl zinc chloride double salt. salt, N-β-hydroxyethylaniline chloride zinc chloride double salt, N-(para-diazophenyl)-morpholine chloride zinc chloride double salt, P-diazo N,N-di-
Normal propylaniline chloride zinc chloride double salt, P-
Diazo-N-ethyl, N-normal propyl aniline chloride zinc chloride double salt, 2-hydroxy 2'-N (para-diazo, N-methylaniline) ethyl ether chloride zinc chloride double salt, para-diazo N-ethyl, N-Hydroxyethylmethatoluidine chloride zinc chloride double salt, 2
-Hydroxy 2'-N-(paradiazo, N-ethylaniline)ethyl ether chloride zinc chloride double salt, para-diazo-N-tashary-pluthianiline chloride zinc chloride double salt, 4-benzoylamino-2,5-di Ethoxybenzenediazonium chloride zinc chloride double salt, 4-(4'-
methoxybenzoylamino)-2,5-diethoxybenzenediazonium chloride zinc chloride double salt, 4-(para-
Examples include (toluylmercapto)-2,5-dimethoxybenzenediazonium chloride zinc chloride double salt, and complex salts of these fluoroboric acids. It is also possible to use so-called diazo polymers having a large number of diazo groups. Examples of couplers that form dyes by coupling with diazonium salts in a weakly basic environment include phenol, resorcinol, phloroglucin, α-naphthol, β-naphthol, dihydroxynaphthaleneoxynaphthoic acid derivatives, pyrazolone derivatives, and β-diketone acids. derivatives, oxydiphenyl derivatives, etc.

Examples of basic substances include thiazole derivatives, pyrrole derivatives, pyrazole derivatives, pyrimidine derivatives, piperidine derivatives, indole derivatives, imidazole derivatives, triazole derivatives, morpholine derivatives, polymethyllentetramine polymer quinoline derivatives, guanidine derivatives, pyridine derivatives, and hydrazine derivatives. , primary amines, secondary amines, tertiary amines, diamines, etc.

Diazonium compounds, couplers, and basic substances tend to develop color when mixed as they are, so one of these three components can be mixed with a fine powder containing wax or fatty acid amide that melts at 50°C to 150°C. By incorporating these two components into the adhesive, a stable paint can be obtained.

Stability can be further increased by using coupling inhibitors, stabilizers, and antioxidants as other additives.

Examples of coupling inhibitors include phosphoric acid, boric acid, tartaric acid, citric acid, lactic acid, oxypyridine, pyrazolonecarboxylic acid, oxyquinoline, and oxybenzotriazole.

Zinc chloride is the most effective stabilizer.

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, the leuco dye and developer,
It is preferable that the mixed liquid does not develop color, aggregate, or become highly viscous when mixed with a diazonium compound coupler and a basic substance, and that the formed heat-sensitive recording layer film is It is required to be strong and not have a 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 adhesive such as styrene-butadiene latex, vinyl acetate.
Emulsified animals of acrylic ester copolymer emulsion, polyurethane emulsion, polyvinyl chloride emulsion, polyvinylidene chloride emulsion, methacrylic ester copolymer emulsion, and acrylic ester copolymer 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 thermosensitive coloring layer may contain a pigment, particularly a white pigment, if necessary. Such pigments include, for example, 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 Examples include inorganic fine powders such as calcium carbonate and silica, and organic resin fine powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin.

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 stearamide,
Stearic acid ethylene bisamide, oleic acid amide,
Fatty acid amides such as palmitylic acid amide, coconut fatty acid amide, and behenic acid amide, waxes (or lubricants) such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, dimethyl terephthalate, terephthalic acid Dibutyl ester, terephthalic acid dibenzyl ester, isophthalic acid dibutyl ester, 1-hydroxynaphthoic acid phenyl ester, 1,2-di(3-methylphenoxy)ethane, 1,2-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),
Examples include sensitizers such as 2-(2'-hydroxy-5'-methylphenyl)-benzotriazole and 2-hydroxy-4-benzyloxybenzophenone, antioxidants, and ultraviolet absorbers.

In the case of the leuco dye type, the heat-sensitive coloring layer contains the leuco dye, an organic acidic substance, and an adhesive as the main components, and in the case of the diazo type, the main components are a diazonium compound, a coupler basic substance, and an adhesive, and are crosslinked as necessary. It can be obtained by coating one side of the support with a paint containing a white pigment, a dispersant, a surfactant, and a heat-accessible substance.

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 after drying is 2 to 13 g/m2, preferably 3 to 1
It is adjusted so that it becomes 0g/m2.

In addition, the stability of recording on thermal recording media, especially leuco dye type, for example, when the recorded material is at a high temperature of 50°C to 60°C, at a temperature of 80% RH to
Necessary because it does not reduce recording density even when stored in high humidity conditions of 90% RH or comes into contact with plasticizers contained in erasers, PVC films, etc., or to provide water resistance, gloss, and writability. Accordingly, an overcoat layer can be provided on the thermosensitive coloring layer.

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 0.5g/m2 to 10g/m2, preferably 1g/m2
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, sensitized vinyl-vinyl acetate copolymer resin, acrylic ester resin, butyral resin, polyester resin, nitrocellulose resin, styrene resin, styrene-acrylic copolymer resin, etc. It can be adjusted 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 lubricant.

UV-curable paints are made of UV-curable resins consisting of photopolymerizable monomers such as various ethylene derivatives, prepolymers or polymers such as unsaturated polyester, epoxy, acrylic, various polyesters, and photopolymerization initiators. It can be adjusted by adding white pigments, lubricants, etc.

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

For UV-curable paints and EB-curable paints, the coating amount is 0.1 g/m2 to 10 g/m on the first overcoat layer.
2. It is preferably applied at a coating weight of 0.5 g/m2 to 8 g/m2.

〔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, "parts" indicate "parts by weight."

Manufacturing Example 1 of Support (1) Base layer A Polypropylene 8 with melt index (MI) 0.8
Calcium carbonate 2 with an average particle size of 1.0 microns in 0 parts by weight
0 parts by weight was blended, kneaded in an extruder set at 270°C, extruded into a sheet, and cooled in a cooling device to obtain a non-stretched sheet.

This sheet was heated to 145°C and then stretched 5 times in the machine direction.

(2) Paper-like layer B, surface layer C: 50 parts by weight of polypropylene with an MI of 4.0 and an average particle size of 1.
A paper-like layer B mixture containing 50 parts by weight of 0 μm calcium carbonate powder and a surface layer C mixture (not including inorganic fine powder) containing 50 parts by weight of MI4.0 polypropylene and 50 parts by weight of high-density polyester were separately prepared. After melt-kneading at 270°C using an extruder, then supplying each to one die and laminating within the die, both sides of the base material layer sheet stretched 5 times in the longitudinal direction obtained in (1) above The surface layer C, which does not contain calcium carbonate powder, is the outer layer. Next, this 5-layer laminate was heated to 185° C. and then stretched 7.5 times in the transverse direction to obtain a 5-layer film.

(3) The surface layer of this 5-layer laminated film is treated with corona discharge, and the thickness of each film of C/B/A/B/C is 3/17.
A 5-layer structure of /40/17/3 microns was obtained.

The Oken Bekk smoothness of the surface layer C of this five-layer structure is 45
It was 0 seconds.

In addition, for protrusions with a height of 5 μm or more on the surface, 0.1
There were 13 pieces per m2.

Example 2 (1) Base layer A Polypropylene 8 with melt index (MI) 0.8
0 parts by weight and 8 parts by weight of high-density polyethylene were blended with 20 parts by weight of calcium carbonate with an average particle size of 1.0 microns, kneaded in an extruder set at 270°C, extruded into a sheet, and cooled with a cooling device. It was cooled to obtain a non-stretched sheet. This sheet was heated to 145°C and then stretched 5 times in the machine direction.

(2) Paper-like layer B, surface layer C: 50 parts by weight of polypropylene with an MI of 4.0, 5 parts by weight of maleic acid (modifying monomer) modified polypropylene with a maleic acid content of 0.5 parts by weight, and an average particle size of 1.0 Paper-like layer B composition (modified monomer amount 0.05 parts by weight per 100 parts by weight of filler) mixed with 46 parts by weight of micron calcium carbonate,
one melt-kneaded after extrusion set at 270°C;
The above (
Coextrusion was performed on one side of the 5-fold stretched sheet in the longitudinal direction obtained in 1) so that the layer C containing polypropylene was on the outside.

On the other hand, a molten film of the paper-like layer B composition was laminated on the other side of the film base layer A using another extruder.

The four-layer laminate thus obtained was heated to 155°C and then stretched 7.5 times in the transverse direction.

(3) The surface of this four-layer laminated film is treated with corona discharge, and the thickness of each film of C/B/A/B is 5/10/50.
/20 micron four-layer structure was obtained.

The Oken Bekk smoothness of the surface C of this four-layer structure was 410 seconds. Back side B was 200 seconds. Further, the number of convex portions of 5 μm or more on the surface C was 5 per 0.1 m 2 .

Example 3 (1) Base layer A Polypropylene 7 with melt index (M1) 0.8
16 parts by weight of calcium carbonate with an average particle size of 1.0 microns was blended with a mixture of 9 parts by weight and 5 parts by weight of high-density polyethylene, kneaded in an extruder set at 270°C, extruded into a sheet, and cooled with a cooling device. It was cooled to obtain a non-stretched sheet. This sheet was heated to 140°C and then stretched 5 times in the machine direction.

(2) Paper-like layer B, surface layer C: MI4.0 polypropylene (surface layer), M14.0
Paper-like layer B composition prepared by mixing 55 parts by weight of polypropylene with 45 parts by weight of calcium carbonate having an average particle size of 1.0 μm was melt-kneaded in a separate extruder, laminated in a die, and coextruded to produce the above-mentioned sheet. Surface layer C on both sides of the 5 times stretched sheet of (1)
Laminated so that the outside is on the outside, then cooled to 60℃,
It was heated to about 130°C, stretched 7.5 times in the transverse direction with a tenter, annealed at 165°C, cooled to 60°C, and the edges were slit to form a 5-layer structure (C/B/A/B/ C
) synthetic paper was obtained.

The wall thickness of this item is C/B/A/B/C=3μ/20μ
/45μ/20μ/3μ, and the surface smoothness was 650 seconds. The number of protrusions of 5 μm or more on the surface layer of the obtained synthetic paper was 10 per 0.1 m 2 .

Example 4 (1) Base layer A Polypropylene 7 with melt index (MI) 0.8
16 parts by weight of calcium carbonate with an average particle size of 1.0 microns is blended into a mixture of 9 parts by weight and 5 parts by weight of high-density polyethylene, and after kneading in an extruder set at 270°C, it is extruded into a sheet and cooled. The mixture was cooled to obtain a non-stretched sheet.

This sheet was heated to 140°C and then stretched 5 times in the machine direction.

(2) Paper-like layer B, surface layer C A composition in which polypropylene C with an MI of 4.0 and 45 parts by weight of calcium carbonate with an average particle size of 1.0 μ are mixed with 55 parts by weight of polypropylene with an MI of 4.0 (paper-like layer). The sheets were melt-kneaded in separate extruders, laminated in a die and co-extruded, and the sheets were laminated on both sides of the 5x stretched sheet of (1) so that the surface layer was on the outside, and then cooled to 60°C. After, about 160
℃, stretched 7.5 times in the transverse direction with a tenter, and
It was annealed at 65°C, cooled to 60°C, and the edges were slit to obtain a synthetic paper with a five-layer structure (C/B/A/B/C).

The wall thickness of this item is C/B/A/B/C=10μ/15
μ/40μ/15μ/10μ, and the surface smoothness is 30
It was 00 seconds. The number of convex portions of 5 μm or more on the surface layer of this product was 3 per 0.1 m 2 .

Example 5 (1) Base layer A Polypropylene 8 with melt index (MI) 0.8
Calcium carbonate 2 with an average particle size of 1.0 microns in 0 parts by weight
0 parts by weight was blended, kneaded in an extruder set at 270°C, extruded into a sheet, and cooled in a cooling device to obtain a non-stretched sheet.

This sheet was heated to 145°C and then stretched 5 times in the machine direction.

(2) Paper-like layer B, surface layer C Paper-like layer B mixture of 50 parts by weight of polypropylene with MI4.0 and 50 parts by weight of calcium carbonate powder, and 50 parts by weight of polypropylene with MI4.0 and 50 parts by weight of high-density polyethylene. The surface layer C mixture was melt-kneaded at 270°C using separate extrusions, then each was fed to one die and laminated within the die, and then the longitudinal direction obtained in (1) above was Both sides of a 5-fold stretched sheet A were coextruded so that the surface layer C, which did not contain calcium carbonate powder, was on the outside. Next, this 5-layer laminate was heated to 185° C. and then stretched 7.5 times in the transverse direction to obtain a 5-layer film.

(3) The surface layer of this 5-layer laminated film is treated with corona discharge, and the thickness of each film of C/B/A/B/C is 1/19
/40/19/1 micron five-layer structure was obtained. This 5
The Bekk smoothness of the surface C of the layered structure was 420 seconds.

Further, the number of convex portions of 5 μm or more on the surface C was 45 per 0.1 m 2 .

Example 6 (for comparison) (1) Base layer A Polypropylene 7 with melt index (MI) 0.8
16 parts by weight of calcium carbonate with an average particle size of 1.0 microns was blended with a mixture of 9 parts by weight and 5 parts by weight of high-density polyethylene, kneaded in an extruder set at 270°C, extruded into a sheet, and cooled with a cooling device. It was cooled to obtain a non-stretched sheet A.

This sheet was heated to 140°C and then stretched 5 times in the machine direction.

(2) Paper-like layer B 55 parts by weight of polypropylene with an MI of 4.0 and an average particle size of 1.
A paper-like layer B composition mixed with 45 parts by weight of calcium carbonate of 0 μm was melt-kneaded using an extruder, extruded from a die into a sheet, which was laminated on both sides of the stretched sheet of (1) above, and then heated to 60°C. After cooling, it was heated to about 160°C, stretched 7.5 times in the transverse direction with a tenter, annealed at 165°C, cooled to 60°C, and the edges were slit (B/A
A synthetic paper with a three-layer structure of /B=25μ/45μ/25μ) was obtained.

The surface smoothness of the surface layer B of this product was 500 seconds. The number of protrusions of 5 μ or more on the surface layer B of this product is 0.1 m
There were 85 pieces per 2 pieces.

The 5-layer laminate was heated to 185° C. and then stretched 7.5 times in the transverse direction to obtain a 5-layer film.

Preparation of Leuco Dye Type Thermosensitive Coloring Layer Paint Solution A (Thermosensitive Coloring Dye Dispersion) 3-(N-ethyl-N-cyclohexylamino)-6-methyl- 7-anilinofluorane 5 parts 10% methyl vinyl ether- Maleic anhydride copolymer aqueous solution 5 parts Water 8 parts Liquid B (color developer dispersant) 2,4-dihydroxy-diphenylsulfone 30 parts 10% methyl vinyl ether-maleic anhydride copolymer aqueous solution 30 parts Water 22 parts Liquid A, Each of the B solutions was separately dispersed and pulverized using an Ultra Visco Mill to adjust the average particle size to 1 μm or less.

15 parts of liquid A, 38 parts of liquid B, 33 parts of 60% calcium carbonate slurry, 50 parts of 10% polyvinyl alcohol aqueous solution,
Self-crosslinking acrylic emulsion (Movinyl 760H
Solid content 50%, manufactured by Hoechst Synthesis Co., Ltd.) 15 parts, 30
% zinc stearate aqueous dispersion, 3 parts of 20% stearamide aqueous dispersion, and 20 parts of water were mixed to prepare a heat-sensitive coloring paint (liquid C).

Preparation of overcoat layer paint 10% carboxy modified polyvinyl Alcohol aqueous solution 550 parts 30% polyamide resin 50 parts 60% kaolin dispersion 50 parts Water 150 copies were mixed to obtain an overcoat layer paint (liquid D).

Preparation of paint for diazo type thermosensitive coloring layer Para-diazodiethylaniline chloride zinc chloride double salt 2
Parts by weight were added to 2 parts by weight of ethyl alcohol, and the mixture was heated and dissolved on a 90°C water bath. Next, 10 parts by weight of melted carnauba wax was added to the ethyl alcohol solution and the whole was thoroughly mixed. This was cooled and solidified as a whole. 20 parts by weight of water and 20 parts by weight of glass beads having a diameter of 5 mm were added to this, and a fine powder of carnauba wax containing the diazo compound was produced using a vibrating pulverizer.

Next, by the same operation as above, a fine powder containing 2 parts by weight of 2,3-dihydroxynaphthalene in 10 parts by weight of carnauba wax was prepared. Next, 5 parts by weight of stearylamine (melting point 49-51°C) was directly melted by heating on a 90°C water bath. To this was added 10 parts by weight of melted carnauba wax and mixed well, and after cooling, a fine powder was produced in the same manner as above. Next, 3 parts by weight of a fine powder containing stearylamine, 3 parts by weight of a fine powder containing 2,3-dihydroxynaphthalene, 3 parts by weight of 5% polyvinyl alcohol, 3 parts by weight of water, and 1 weight of a 10% zinc chloride aqueous solution. 10% citric acid aqueous solution was added to bring the whole pH to 3~3.
Adjusted to 4. Finally, 3 parts by weight of fine powder containing para-diazoethylaniline chloride zinc chloride double salt was added to prepare a diazo type thermosensitive coloring layer coating (liquid E).

Examples 1 to 3 A leuco dye type heat-sensitive coloring paint C solution was applied to one side of the synthetic paper having a multilayer structure prepared in Production Examples 1 to 3 with a coating amount of 5.5 g/m2 after drying. I painted it to look like this. Furthermore, overcoat layer paint D liquid was applied on top of it so that the coating amount after drying was 3.0 g/m2, and then smoothed with a super calender, and the smoothness measured according to JIS P 8119 was A thermosensitive recording medium lasting 1,000 seconds was obtained.

Example 4, Example 5 A coating amount of diazo-type heat-sensitive coloring paint E solution after drying was 8.0 g/m2 on one side of the synthetic paper having a multilayer structure prepared in Production Examples 4 and 5. It was painted like this. A heat-sensitive recording material with a smoothness of 1,800 seconds was obtained by supercalendering.

Comparative Example 1, Comparative Example 2 Synthetic paper with multilayer structure created in Production Example 6 (Comparative Example 1
) and commercially available synthetic paper TPG-75 with multilayer structure (
A heat-sensitive coloring layer and an overcoat layer were coated on one side of Oji Yuka Synthetic Paper Co., Ltd. (Comparative Example 2) in the same manner as in Example 1, followed by supercalender treatment to obtain a heat-sensitive recording material.

Table 1 shows the results of printing on the thermal recording bodies obtained in Examples and Comparative Examples using a commercially available thermal plotter (NS SP-FAX manufactured by Nippon Steel Corporation).

White missing spots: Number of white missing spots per 1 m2 when performing solid recording ○: 10 pieces/m2 or less, ×: 31 pieces/m2 or more Example 1
~The thermosensitive recording material obtained in Example 5 had no line breaks or white spots, and a recording with good uniformity was obtained, whereas Comparative Example 1
The thermosensitive recording material obtained in Comparative Example 2 had line breaks and white spots, and could not be used as plotter paper.

〔Effect of the invention〕

According to the present invention, when thin line recording or solid recording is performed using a thermal printer or plotter, it is possible to obtain a recording with good uniformity without line breakage or white spots.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an example of a heat-sensitive recording material, FIG. 2 is an enlarged schematic cross-sectional view of a support used in the present invention, and FIG. 3 is a cross-sectional view of a support used in Comparative Example 1. 1 is a support, 2 is a thermosensitive coloring layer, 3 is an overcoat, 4
5, 6 are fine powders, 7 are fine holes, 8 is a protrusion, 9 is the apex of the protrusion, A is the base layer of the support, B is the paper layer of the support, C Patent applicant for the surface layer of the support Agent for Oji Paper Co., Ltd. Hirotoshi Nakamoto Akito Inoue Katsura Yoshine

Claims (1)

[Claims] [Claim 1] A heat-sensitive recording material having a structure in which a synthetic paper having a multilayer structure is used as a support, and a heat-sensitive coloring layer and, if necessary, an overcoat layer are successively provided on one side of the support, wherein the support is made of an inorganic material. A surface layer consisting of a thermoplastic resin film containing 0 to 3% by weight of fine powder and 8 to 8% by weight of inorganic fine powder.
The film has a multilayer structure including a paper-like layer made of a thermoplastic resin film containing 65% by weight, and the protrusions protruding from the flat surface of the surface layer have a height of 5 μm or more. A heat-sensitive recording material characterized in that the number of heat-sensitive recording materials is 50 or less per m2.