JPH06247050A - Heat sensitive recording material - Google Patents

Abstract

PURPOSE:To provide a heat sensitive recording material which improves the problem of a polyamide epichorohydrin crosslinking agent to be used as a crosslinking agent of resin of an overcoat layer, undercoat layer and backcoat layer of a heat sensitive color development layer, is superior in water resistance and plasticizer resistance, has favorable head matching properties and does not generate breaking of a heat sensing head by electrolytic corrosion. CONSTITUTION:An overcoat layer or an undercoat layer or a backcoat layer consisting mainly of resin and a crosslinking agent is provided on a heat sensitive color development layer and polyamide epichlorohydrin resin having contents of organic chlorine compound of not exceeding 1wt.% is used as the crosslinking agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to an improvement of a heat-sensitive recording material having a support provided with a heat-sensitive coloring layer which is colored by heat.

[0002]

2. Description of the Related Art A heat-sensitive recording material generally comprises a support such as paper, synthetic paper, plastic film and the like, on which a heat-sensitive color-forming layer containing a thermo-color-forming composition as a main component is provided. A colored image can be obtained by heating with light or a strobe lamp. Compared with other recording materials, this type of recording material can perform recording in a short time with a relatively simple device without performing complicated processing such as development and fixing, and has less noise and environmental pollution. Due to its low cost and other advantages, it is used for copying books, documents, etc., electronic calculators, facsimiles, ticket vending machines,
It is widely used as a recording material in various fields such as labels and recorders. The thermochromic composition used for such a heat-sensitive recording material comprises an ordinary color former and a developer which develops these colorants under heat, and the colorant has, for example, a lactone, a lactam or a spiropyran ring. A colorless or light-colored leuco dye has been conventionally used as a developer, and an organic acid or a phenolic substance has been used. The recording material obtained by combining the color-developing agent and the color-developing agent has the advantage that the color tone of the obtained image is particularly clear, the whiteness of the background is high, and the weather resistance of the image is excellent. Widely used.

However, this kind of thermal recording material is a DO recording material.
When it comes into contact with plasticizers such as A (dioctyl adipate) or DOP (dioctyl phthalate) or oils and fats, the image will be erased, or the background part will be colored with a solvent such as ethanol or ethyl acetate. However, it has been proposed to provide an overcoat layer (protective layer) on the heat-sensitive layer (JP-A-54-128347 and JP-A-54-3594). Gazette). These overcoat layers are mainly composed of a resin and a cross-linking agent that cures the resin, and various cross-linking agents have been proposed in order to impart water resistance to prevent peeling of the overcoat layer due to water. However, even if it is excellent in terms of reactivity, the background color (darkening in the non-printed area), the stability of the overcoat layer coating liquid over time is impaired, and the compatibility with the print head of the printer is poor, and the print head does not easily However, there is a problem that the printed image may be worn out due to the adherence to the printed image or the print head may be damaged.

For the purpose of eliminating unevenness of the support or increasing the sensitivity by not releasing the heat energy during printing, an under layer may be provided between the support and the thermal recording layer, or a print head during printing. Some of them have a back coat layer to prevent the running property and penetration of a plasticizer from the back side, and to prevent sticking (blocking) of heat-sensitive materials to each other when rolled, but the undercoat layer and back coat layer are All of them mainly consist of a resin and a crosslinking agent, and like the overcoat layer, need to have improved water resistance, and many crosslinking agents have also been proposed. Among such cross-linking agents,
Polyamide epichlorohydrin-based cross-linking agents are mentioned as those which are hardened and have particularly excellent water resistance and are relatively well balanced in quality required for other thermal recording papers (JP-A-60-244596, JP-A-60-244596). 61-112
88 publication). However, the polyamide epichlorohydrin-based cross-linking agent contains a low molecular weight organochlorine compound due to manufacturing problems, and when used as a curing agent for a resin, the low molecular weight organochlorine compound reacts with the resin to produce a high molecular weight organochlorine compound. Since the curing reaction with the resin is impeded, the plasticizer resistance of the heat-sensitive layer is lowered, and the low molecular weight organochlorine compound and the reaction product become dust during printing and adhere to the print head, which causes blur of the printed image. Furthermore, the amount of organic chlorine compounds in the heat-sensitive recording material is unnecessarily increased, which causes dot breakage due to damage of the print head, so-called head electrolytic corrosion (organic chlorine compounds are a cause of head electrolytic corrosion. Is well known). As described above, the polyamide epichlorohydrin-based cross-linking agent is still insufficient in many cases.

[0005]

DISCLOSURE OF THE INVENTION The present invention has improved the above-mentioned polyamide epichlorohydrin-based cross-linking agent and is excellent in water resistance and plasticizer resistance, has good head matching property, and causes damage to a thermal head due to electrolytic corrosion. The object is to provide a heat-sensitive recording material that does not have heat.

[0006]

According to the present invention, in a thermosensitive recording material having a thermosensitive coloring layer which is colored by heat on a support, an overcoat containing a resin and a crosslinking agent as a main component is formed on the thermosensitive coloring layer. A heat-sensitive recording material is provided which is provided with a coat layer and uses a polyamide epichlorohydrin resin having an organic chlorine compound content of 1% by weight or less as the crosslinking agent. Further, according to the present invention, in a thermosensitive recording material having a thermosensitive coloring layer that is colored by heat on a support, an undercoat layer containing a resin and a crosslinking agent as a main component is provided on the thermosensitive coloring layer, and the crosslinking Provided is a heat-sensitive recording material characterized by using a polyamide epichlorohydrin resin having an organic chlorine compound content of 1% by weight or less as an agent. Further, according to the invention, in a thermosensitive recording material having a thermosensitive coloring layer which is colored by heat on a support, a backcoat layer containing a resin and a crosslinking agent as main components is provided on the back surface of the support, and the crosslinking agent As a heat-sensitive recording material, a polyamide epichlorohydrin resin having an organic chlorine compound content of 1% by weight or less is used.

The present invention provides a thermosensitive recording material having a thermosensitive coloring layer provided on a support, an overcoat layer is provided on the thermosensitive coloring layer, or an undercoat layer is provided between the support and the thermosensitive coloring layer, or A back coat layer is provided on the back surface of the support, and the low-molecular organic chlorine compound of the polyamide epichlorohydrin resin is reduced as a cross-linking agent in each of the overcoat layer, the undercoat layer or the backcoat layer, and the organic compound in the crosslinker resin component is reduced. Chlorine compound content is 1%
The following content provides a heat-sensitive recording material having good head matching properties, low head electrolytic corrosion resistance, and excellent plasticizer resistance and water resistance.

Next, the head electrolytic corrosion when the polyamide epichlorohydrin resin according to the present invention is used as a crosslinking agent will be described in detail. The effect of suppressing head electrolytic corrosion by the cross-linking agent of the present invention is greatest when the present cross-linking agent is used in the overcoat layer, but of course, it is also effective when used in the undercoat layer or the backcoat layer. Incidentally, compared with the case of providing an overcoat layer containing a crosslinking agent of the present invention on an undercoat layer or a backcoat layer using a crosslinking agent an amide epichlorohydrin resin containing a conventional low molecular weight organic chlorine compound, an undercoat layer or When the cross-linking agent of the present invention is used as the cross-linking agent of the back coat layer and an overcoat layer containing the cross-linking agent of the present invention is further provided, the effect of suppressing head electrolytic corrosion is improved.

When a conventional amide epichlorohydrin resin cross-linking agent containing a low molecular weight organochlorine compound is used in the overcoat layer and the cross-linking agent of the present invention is used in the undercoat layer or the backcoat layer, The effect of the organic chlorine compound of the overcoat layer, which is the contact portion of the thermal head, is great, and the effect is not so great even if the crosslinking agent of the present invention is used for the undercoat layer and the backcoat layer, but the water resistance and plastic resistance With respect to the drug properties, it is possible to obtain a compound having superior properties to the undercoat layer and the backcoat layer using the conventional polyamide epichlorohydrin-based crosslinking agent.

In the present invention, the addition amount of the cross-linking agent is 0.1 to 1 part by weight with respect to 1 part by weight of the resin because the electrolytic corrosion resistance of the head is small, and the plasticizer resistance and water resistance are low. However, it is more preferable that the amount is 0.3 to 0.51 parts by weight. Further, in the present invention, a crosslinking agent such as boric acid, epoxy, aziridine, glycidylamine, glyoxal, or a methylol group-containing compound which has been conventionally used can be used in combination with the crosslinking agent.

As the resin which can be used in the present invention, generally used resins such as polyvinyl alcohol, cellulose derivatives, starch and its derivatives, carboxyl group modified polyvinyl alcohol, polyacrylic acid and its derivatives, styrene / acryl. Acid copolymers and their derivatives, poly (meth) acrylamides and their derivatives, styrene / acrylic acid / acrylamide copolymers, amino group modified polyvinyl alcohol, epoxy modified polyvinyl alcohol, polyethyleneimine, aqueous polyester, aqueous polyurethane, isobutylene / Maleic anhydride copolymer and its derivatives, polyester,
Examples thereof include polyurethane, acrylic acid ester (co) polymers, styrene / acrylic copolymers, epoxy resins, polyvinyl acetate, polyvinylidene chloride, polyvinyl chloride and derivatives thereof. The above resins are not particularly limited, but water-soluble resins are particularly preferable in consideration of chemical resistance.

In the overcoat layer according to the present invention, in addition to the above resin / crosslinking agent, conventionally used auxiliary additive components such as fillers, surfactants, heat-fusible substances (or A lubricant), a pressure color-developing inhibitor, etc. can be used in combination. In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, inorganic fine powder such as surface-treated calcium or silica, etc. , Urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin, and other organic fine powders. Examples of heat-fusible substances include higher fatty acids or esters, amides or metal salts thereof, various waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoate esters, higher linear glycols, 2, 4-Epoxy-dialkyl hexahydrophthalate, higher ketones, p-benzyl biphenyl, and other heat-fusible organic compounds such as those having a melting point of about 50 to 200 ° C. may be mentioned.

As a method of developing color by heat of the present invention,
There are those that utilize the color development reaction between the leuco dye and the color developer, those that utilize the reaction of the diazo compound and coupler, and those that utilize the reaction of the isocyanate and amine. In the present invention, the color developing method is not particularly limited, but here, the method using a general leuco dye will be described. The leuco dyes used in the present invention may be applied alone or as a mixture of two or more kinds, and as such leuco dyes, those applied to the heat-sensitive material of this kind are arbitrarily applied, for example, triphenylmethane-based Leuco compounds of dyes such as fluoran type, phenothiazine type, auramine type, spiropyran type, and indinophthalide type 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-diethylaminophthalide,
3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide, p-cyclohexylamino-6-chlorofluorane, p-dimethylamino-5, 7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3
-Diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3
-(Np-tolyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoro) Rumethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6-bis (diethylamino)
-9- (o-Chloranilino) xanthyl benzoate lactam}, 3-diethylamino-6-methyl-7- (m-
Trichloromethylanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-
N-methyl-N-amylamino-6-methyl-7-anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7 -Anilino Fluoran,
3- (N, N-diethylamino) -5-methyl-7-
(N, N-dibenzylamino) fluorane, benzoylleuco methylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrrilospirane, 6'-bromo-
3′-methoxy-benzoindolino-pyrrilospirane,
3- (2'-hydroxy-4'-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-diethylemino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7
-(Di-p-chlorophenyl) methylanilinofluorane, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-p
-Toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- (α-phenylethylamino)
Fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methyltoluidino)-
7- (pn-butylanilino) fluorane, 3- (N
-Benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4'-bromofluorane, 3-diethylemino-6-methyl-7-mesitidino-4 ', 5'-benzofluorane , 3-diethylemino-6-methyl-7- (2 ', 4'-dimethylanilino)
Fluoran,

As the color developer used in the present invention, various electron-accepting compounds that cause the leuco dye to develop color upon contact, such as phenolic compounds, thiophenolic compounds, thiourea derivatives, organic acids and their metals. Salts and the like are preferably applied, and specific examples thereof include the following.

4,4'-isopropylidene bisphenol, 4,4'-isopropylidene bis (o-methylphenol), 4,4'-secondary butylidene bisphenol, 4,4'-isopropylidene bis (o-tertiary) Butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol),
2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis (6
-Tert-butyl-2-methyl) phenol, 1,
1,3-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-Tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4 ′ -Thiobis (6-tert-butyl-2-methyl) phenol, 4,4'-diphenol sulfone, 4,2'-diphenol sulfone,
4-isopropoxy-4'-hydroxydiphenylphone, 4-benzyloxy-4'-hydroxydiphenylphone, 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, 2, 2'-methylenebis (4-ethyl-6-tert-butylphenol),
1,3-bis (4-hydroxyphenylthio) -2-hydroxypropane, N, N′-diphenylthiourea,
N, N'-di (m-chlorophenyl) thiourea, salicylanilide, 5-chloro-salicylanilide, salicyl-o-chloroanilide, 2-hydroxy-3-naphthoic acid, zinc thiocyanate antipyrine complex, 2-acetyl Oxy-3-naphthoic acid zinc salt, 2-hydroxy-
Metal salts of 1-naphthoic acid, 1-hydroxy-2-naphthoic acid, hydroxynaphthoic acid such as zinc, aluminum and calcium, bis- (4-hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester Ester, 1,3-bis (4-hydroxyphenyl) benzene, 1,4-bis (4-hydroxyphenyl) benzene, 2,4′-diphenol sulfone,
3,3′-diallyl-4,4′-diphenol sulfone, α, α-bis (4-hydroxyphenyl) -α-methyltoluene, zinc thiocyanate antipyrine complex,
Tetrabromobisphenol S etc.

In the present invention, various conventional binders can be used for binding and supporting the leuco dye, the color developer and the auxiliary component on the support. For example, polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinyl hirolidone, acrylamide / acrylic ester copolymer, acrylamide / acrylic ester. / Methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein and other water-soluble polymers, and poly Vinyl acetate, polyurethane, polyacrylic ester,
Examples include emulsions such as polymethacrylic acid ester and ethylene / vinyl acetate copolymers, and latexes such as styrene / butadiene copolymers and styrene / butadiene / acrylic copolymers, but avoid those containing chlorine. Should be.

In the present invention, the leuco dye, the color developer and the auxiliary component may be used, if necessary, in combination with an auxiliary additive component such as a filler or a surfactant which is commonly used in this type of heat-sensitive recording material. can do. In this case, as the filler, for example, in addition to calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, inorganic fine powder such as surface-treated calcium and silica, Examples include organic fine powders of urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene and the like.
The heat-sensitive recording material of the present invention is used in various fields. In particular, the heat-sensitive recording type label sheet and the heat-sensitive recording type magnetic ticket paper are used by utilizing the above-described excellent color-developed image and stability of the background part. It can be used to advantage. In the case of a heat-sensitive recording type label sheet, a thermosensitive coloring layer containing the above-mentioned leuco dye and a developer and a protective layer are provided on one surface of the support, and a release liner is provided on the other surface of the support via an adhesive layer. Should be provided, in the case of magnetic ticket paper, instead of this peeling mount,
A magnetic recording layer containing a ferromagnetic material and a binder as main components may be provided.

[0019]

[Formation of thermosensitive coloring layer]

(Liquid A) 3- (N-cyclohexyl-N-methyl) amino-6-methyl-7-anilinofluorane 10 parts 10% Hydroxyethylcellulose aqueous solution 20 parts Water 60 parts (Liquid B) 10 parts Bisphenol A 5 parts Carbonic acid Calcium 5 parts Stearic acid amide 20 parts 10% polyvinyl alcohol aqueous solution 60 parts Water The above solutions A and B are dispersed in a sand mill so that the average particle diameter is 2 μm or less. Thus obtained solution A (1 part), solution B (8 parts) and 10% polyvinyl alcohol aqueous solution (1 part) are mixed and stirred to obtain a thermosensitive coloring layer coating solution. This coating solution is applied on a commercially available high-quality paper having a basis weight of 52 g / ² or on an undercoat layer provided on the high-quality paper so as to have a dry adhesion amount of 6 g / m ² , and dried to form a thermosensitive coloring layer. . [Formation of undercoat layer] (C liquid) Kaolin 10 parts 10% polyvinyl alcohol aqueous solution 1 part Water 89 parts The above C liquid is dispersed in a sand mill so that the average particle diameter is 2 μm or less. (Solution D) Solution C 50 parts 10% Carboxyl-modified polyvinyl alcohol aqueous solution 10 parts Polyamide epichlorohydrin treated to have an organochlorine compound content as shown in the preparation method of the heat-sensitive recording materials of Examples and Comparative Examples. Resin cross-linking agent and substitutes (concentration of solid content: 10%) 1 part Water 39 parts The above D liquid is applied and dried on a commercially available high-quality paper having a basis weight of 52 g / ^{2 so} as to have a dry adhesion amount of 6 g / m ^2. An undercoat layer is formed. [Formation of overcoat layer] (E liquid) C liquid 40 parts 10% polyvinyl alcohol aqueous solution 40 parts In order to have the content of the organic chlorine compound as shown in the preparation method of the heat-sensitive recording materials of Examples and Comparative Examples. Treated polyamide epichlorohydrin resin cross-linking agent and alternatives (solid content concentration 10%) 4 parts Zinc stearate (30%) 2 parts Water 12 parts Drying amount of the above E solution will be 3.6 g / m ² . So that it is coated on the thermosensitive coloring layer. [Formation of back coat layer] (F liquid) C liquid 30 parts 10% polyvinyl alcohol aqueous solution 40 parts In order to have the content of the organic chlorine compound as shown in the preparation method of the heat-sensitive recording materials of Examples and Comparative Examples. Treated polyamide epichlorohydrin resin cross-linking agent and its substitute (solid content concentration 10%) 4 parts The above-mentioned solution F was applied on the back surface of the support so that the dry adhesion amount was 3 g / m ² , and the back coat layer was formed. obtain.

Example 1 A heat-sensitive layer was directly formed on the support by the above-mentioned method using the above-mentioned heat-sensitive color-developing layer coating solution obtained from solution A, solution B or the like. Further, a low molecular weight organochlorine compound in the polyamide epichlorohydrin resin crosslinker is treated to obtain an over-treatment using the above-mentioned E liquid using the crosslinker in which the content of the organochlorine compound in the crosslinker is 0.3%. A thermal recording material of Example 1 having a coat layer was prepared.

Example 2 In Example 1, except that a crosslinking agent having an organochlorine compound content of 0.6% was used as the crosslinking agent instead of the organochlorine compound content of 0.3%. A thermal recording material of Example 2 having an overcoat layer was prepared in the same manner as in Example 1.

Comparative Example 1 Example 1 was repeated except that a cross-linking agent having an organochlorine compound content of 12% was used as the cross-linking agent instead of the cross-linking agent having an organochlorine compound content of 0.3%. A thermal recording material of Comparative Example 1 having an overcoat layer was prepared in the same manner as in Example 1.

Comparative Example 2 Example 2 was repeated except that a cross-linking agent having an organochlorine compound content of 24% was used as the cross-linking agent instead of the cross-linking agent having an organochlorine compound content of 0.3%. A thermal recording material of Comparative Example 2 having an overcoat layer was prepared in the same manner as in Example 1.

Comparative Example 3 In the same manner as in Example 1 except that a cross-linking agent containing a methylol resin was used as the cross-linking agent instead of the cross-linking agent having an organochlorine compound content of 0.3%. A thermal recording material of Comparative Example 3 having an overcoat layer was prepared.

Example 3 A low-molecular organochlorine compound in a polyamide epichlorohydrin resin cross-linking agent was treated on a support to use a cross-linking agent in which the content of the organochlorine compound in the cross-linking agent was 0.3%. An undercoat layer was provided using the C liquid. A on it
A heat-sensitive recording material of Example 3 having an undercoat layer was prepared by forming a heat-sensitive layer by the above-mentioned method using the above-mentioned heat-sensitive color developing layer coating solution obtained from solution B or the like.

Comparative Example 4 The procedure of Example 3 was repeated except that a cross-linking agent having an organochlorine compound content of 12% was used instead of the cross-linking agent having an organochlorine compound content of 0.3%. A thermal recording material of Comparative Example 4 having an undercoat layer was prepared in the same manner as in Example 3.

Comparative Example 5 The same procedure as in Example 3 was repeated except that a cross-linking agent containing a methylol resin was used as the cross-linking agent instead of the cross-linking agent having an organochlorine compound content of 0.3%. A thermal recording material of Comparative Example 5 having an undercoat layer was prepared.

Example 4 A heat-sensitive layer was directly formed on a support by the above-mentioned method using the above-mentioned heat-sensitive color forming layer coating solution obtained from solution A, solution B or the like. On the back surface of the support provided with the heat-sensitive layer, a low molecular weight organochlorine compound in the polyamide epichlorohydrin resin crosslinker was treated to use a crosslinker in which the content of the organochlorine compound in the crosslinker was 0.3%. A thermosensitive recording material of Example 4 having a back coat layer was prepared using the E liquid.

Comparative Example 6 The procedure of Example 4 was repeated except that a cross-linking agent having an organochlorine compound content of 12% was used instead of the cross-linking agent having an organochlorine compound content of 0.3%. A thermal recording material of Comparative Example 6 having a back coat layer was prepared in the same manner as in Example 4.

Comparative Example 7 The same procedure as in Example 4 was repeated except that a cross-linking agent containing a methylol resin was used as the cross-linking agent instead of the cross-linking agent having an organochlorine compound content of 0.3%. A thermal recording material of Comparative Example 7 having a back coat layer was prepared.

The performance of the thermal recording materials of Examples and Comparative Examples obtained above was evaluated by the following method. The results are shown in Table 1. (1) Thermal head matching property Using a thermal printing device equipped with a thermal head manufactured by Matsushita Electronic Parts Co., Ltd., a head voltage of 24 V and a printing energy of 0.45.
Under the conditions of W / dot and pulse width of 1 msec, 100 m printing is performed and the change of the printed image is observed. Adhesion amount of head shavings ○: There is no blur of the printed image due to the adhesion of head shavings △: There is a slight blur of the printed image due to the adhesion of head shavings ×: Large blur of the printed image due to the adhesion of head shavings ○: White spots in the printed image due to head loss No x: Print image has white spots due to head breakage (2) Dynamic sensitivity Using a thermal printer equipped with a thermal head manufactured by Matsushita Electronics Co., Ltd., head voltage 24 V, printing energy 0.45
Printing was performed under the conditions of W / dot and pulse width of 0.1 to 1.2 msec, the printing energy when the density became 1.0 was calculated by a Macbeth densitometer, and the numerical value of Example 1 was set as 1 as a relative value. The ratio is shown (the larger the sensitivity, the better). (3) Water resistance test The printed thermal recording material was immersed in water at 20 ° C. for 3 hours and then taken out. An overcoat layer provided was an overcoat layer, and a backcoat layer provided was a backcoat. The layer is rubbed with a finger 10 times, and the degree of peeling of the film at that time is observed. Regarding the undercoat layer, it is observed whether the thermosensitive coloring layer and the support are separated. ◎: No peeling ○: No peeling, but the surface is slimy △: A little peeling ×: Complete peeling (4) Plasticizer resistance After printing with a heat block at 150 ° C, measure the density with a Macbeth densitometer A plasticizer DOA (dioctyl adipate), an overcoat layer on the surface of the overcoat layer, and an undercoat layer and a backcoat layer on the back surface of the support and the surface of the backcoat layer with absorbent cotton, respectively. After applying thinly and leaving it at 40 ° C. for 15 hours, the concentration is measured.

[0032]

[Table 1]

[0033]

The heat-sensitive recording material of the present invention is provided with an overcoat layer on the heat-sensitive color-developing layer to reduce the low molecular weight organochlorine compound of the polyamide epichlorohydrin resin as a cross-linking agent, and to reduce the organochlorine compound in the cross-linking agent resin component. Content rate of 1
%, The head matching property is good, there is little head dust adhesion, and there is little head electrolytic corrosion, the print image defects due to head dot breakage are eliminated, and the plasticizer resistance and water resistance are excellent. It becomes a thing. In addition, thermal recording materials that use polyamide epichlorohydrin resin as a cross-linking agent for the undercoat layer and backcoat layer resin can also suppress print image defects due to head dot breakage, and suppress migration of water and plasticizer from the back surface. With this, water resistance and plasticizer resistance are excellent.

Claims (3)

[Claims] 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer which is colored by heat, wherein an overcoat layer comprising a resin and a crosslinking agent as main components is provided on the thermosensitive coloring layer, and an organic layer is used as the crosslinking agent. A heat-sensitive recording material comprising a polyamide epichlorohydrin resin having a chlorine compound content of 1% by weight or less. 2. A thermosensitive recording material having a thermosensitive coloring layer which is colored by heat on a support, wherein an undercoat layer containing a resin and a crosslinking agent as a main component is provided on the thermosensitive coloring layer, and an organic layer is used as the crosslinking agent. A heat-sensitive recording material comprising a polyamide epichlorohydrin resin having a chlorine compound content of 1% by weight or less. 3. A thermosensitive recording material having a thermosensitive coloring layer which is colored by heat on a support, wherein a backcoat layer containing a resin and a crosslinking agent as main components is provided on the back surface of the support, and an organic chlorine is used as the crosslinking agent. A heat-sensitive recording material comprising a polyamide epichlorohydrin resin having a compound content of 1% by weight or less.