JPS61164881A - Thermal recording material - Google Patents

Abstract

PURPOSE:To ensure a high sensitivity, to prevent ground fogging from occurring under hot and humid conditions and to prevent decoloration from occurring on contact with a plasticizer, an oil or the like, by a method wherein a metallic salt of a salicylic acid compound functioning as a color developer and a zinc compound are incorporated individually in an undercoat layer and a thermal color forming layer. CONSTITUTION:One of a metallic salt of a salicylic acid compound and a zinc compound is incorporated in an undercoat layer while the other is incorporated in a thermal color forming layer, in a thermal recording material comprising an undercoat layer and a thermal color forming layer laminated in this order on a base. The metallic salt functions as a color developer for a leuco dye, and is a salt of magnesium, calcium, strontium, barium, aluminum, tin, lead or the like. The zinc compound may be, for example, an inorganic one or an organic one, such as zinc hydroxide, zinc fluoride and zinc benzoate, and is used in an amount of 0.2-0.5pt.wt. per 1pt.wt. of the color developer consisting of the metallic salt of the salicylic acid compound.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to improvements in heat-sensitive recording materials containing leuco dyes as color formers.

[Prior art]

Thermosensitive recording materials generally consist of a support such as paper, synthetic paper, or plastic film provided with a thermosensitive complete image layer containing a thermochromic composition as a main component.
A colored image can be obtained by heating with a spiropyran ring or the like. This kind of recording material has a phenomenon compared to other recording materials,
It has the advantages of being able to obtain records in a short time with a relatively simple device without complicated processes such as fixing, generating less noise and polluting the environment, and being inexpensive.
In addition to being used for copying books, documents, etc., it is also widely used as a recording material in a wide variety of applications, including electronic computers, facsimile machines, ticket vending machines, labels, and recorders. The thermochromic composition used in such heat-sensitive recording materials consists of a general coloring agent and a color developer that causes the coloring agent to develop a specific color under heat.
As the coloring agent, for example, a colorless or light-colored leuco dye having a lactone, lactam or spiropyran ring has been used, and as the color developer, an organic acid or a phenolic substance has been conventionally used. This recording material containing a combination of a color forming agent and a color developer has the advantage that the obtained image has a particularly clear color tone, a high background whiteness, and the image has excellent light resistance, and is widely used. It's being used.

Conventionally, bisphenol A and P-hydroxybenzoic acid esters have been used as color developers for leuco dyes, but these phenols have high color density but lack the stability of colored images, so they are not suitable for natural dyes. There is a problem in that the concentration decreases not only when left standing, but also when it comes into contact with oils and fats such as fingerprints. These phenomena occur not only when using phenols but also when general organic acids are used, and there is a strong desire to overcome them. As seen in JP-A-59-38091, the use of aluminum chloride as at least a part of the color developer has been proposed as a color developer that provides images with good stability. This method also provides a highly reliable thermal paper with almost no decoloring of the image, but it has the disadvantage that the background density is high because liquid fogging occurs at the time the thermal liquid is prepared.

〔the purpose〕

The object of the present invention is to provide a heat-sensitive recording material that improves the above-mentioned conventional drawbacks, that is, to provide a heat-sensitive recording material that is highly sensitive, does not cause background fogging due to humidity, and does not discolor when it comes into contact with plasticizers, oil, etc. The purpose of the present invention is to provide a heat-sensitive recording material that is free of heat.

〔composition〕

According to the present invention, in a heat-sensitive recording material comprising an undercoat layer and a heat-sensitive coloring layer laminated in this order on a support, either one of a metal salt of a salicylic acid compound and a zinc compound is added to the undercoat. In addition to containing it in the layer,
A heat-sensitive recording material characterized in that the other component is contained in the heat-sensitive coloring layer is provided.

The metal salt of the salicylic acid compound used in the present invention acts as a color developer for the leuco dye, and as such a salt, a compound represented by the following general formula (1) is usually used.

It represents a metal atom such as lithium, barium, aluminum, tin or lead, and m represents the valence of a.

Further, R is a hydrogen atom, an alkyl group, or an aryl group.

Represents a substituent such as an alkoxy group, an aralkyl group, or a halogen atom. n represents an integer of 1 to 4, and when n is 2 or more, that is, there are a plurality of R's, each R may be the same or different. Examples of salicylic acid compounds that can form salts with the metal atoms include, but are not necessarily limited to, the following.

Specific examples of the zinc compound used in the present invention include, for example,
Zinc oxide, zinc hydroxide, zinc fluoride, zinc benzoate, P
-zinc tert-butylbenzoate, zinc salicylate, zinc stearate, zinc myristate, zinc laurate,
Examples include inorganic and organic ones such as zinc benzoin, zinc acetylacetonate, zinc p-toluenesulfonate, zinc octylsulfonate, zinc p-tert-butylsulfonate, zinc dimethylglyoxyl, and zinc xanthate. It is not limited to.

The amount of zinc compound used in the present invention is 0.2-5.
It is used in a proportion of 0 parts by weight.

As the color developer used in the present invention, in addition to the metal salt of the salicylic acid compound, if necessary, a color developer made of a conventionally known phenolic substance, an inorganic organic acidic substance, or a derivative thereof may be used in combination. You can also. The color developer used in the present invention is generally used in an amount of 1 to 10 parts by weight, preferably 2 to 6 parts by weight, per 1 part by weight of the leuco dye. The color developer made of salt accounts for 20% by weight or more, preferably 50% by weight or more of the total color developer.

The leuco dyes used in the present invention can be applied singly or in combination of two or more types, but such leuco dyes include:
Those applied to this type of heat-sensitive material can be arbitrarily applied. For example, leuco compounds of dyes such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, and indolinophthalide-based dyes are preferably used. . Specific examples of such leuco dyes include those shown below.

3.3-His(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-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluoran, 3-dimethylamino-5,7-dimethyl Fluorane, 3
-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6
-Methyl-7-chlorofluorane, 3-(N-p-tolyl-N-ditylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-(N-(3'-trifluoromethylphenyl)amino)-6-dinithylaminofluorane, 2-(3,6
-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)
Fluoran, 3-diethylamino-7-(o-chloroanilino)fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran.

3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N,N- diethylamino)-5-methyl-7-(
N.

N-dibenzylamino)fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane, 3-(2'- 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy- 5'-nitrophenyl) phthalide.

3-(2'-hydroxy-41-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2 '-Hydroxy-4'-chloro-5'
-methylphenyl)phthalide.

3-morpholino-7-(N-propyltrifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoro methylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluorane, 3-(N-ethyl -P-)-luidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-(0-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenyl ethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(ρ-n
-butylanilino)fluorane, 3-(N-benzyl-N-cyclohexylamino)-5
, 6-penzo 7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
',5'-benzofluorane, 3.6-simethoxyfluorane, 3-(p-dimethylaminophenyl)-3-phenylphthalide, 3-di(1-ethyl-2-methylyldol)-3 -yl-phthalide, 3-diethylamino-6-phenyl-7-azafluorane.

3.3-bis(p-diethylaminophenyl)-6-dimethylaminophthalide, 2-bis(p-dimethylaminophenyl)methyl-5-
Dimethylamino-benzoic acid, 3-(ρ-dimethylaminophenyl)-3-(p-dibenzylaminophenyl)phthalide, 3-(N-ethyl-Nn-amyl)amino-6-methyl-7- Anilitufluoran et al.

In the present invention, various electron-accepting substances that react with the leuco dye to color it when heated are used as the color developer that can be used in combination with the color developer made of a metal salt of a salicylic acid compound. Specific examples include phenolic substances, organic or inorganic acidic substances, and esters and salts thereof as shown below.

gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di-tert-
Butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4'-isopropylidenediphenol,
4.4'-isopropylidene bis(2-chlorophenol), 4,4'-isopropylidene bis(2,6-dibromophenol), 4.4'-isopropylidene bis(
2,6-dichlorophenol), 4゜4'-isopropylidene bis(2-methylphenol), 4,4'-isopropylidene bis(2,6-dimethylphenol), 4
, 4'-isopropylidene bis(2-t, ert, -butylphenol), 4.4'-5ec-butylidene diphenol, 4,4'-cyclohexylidene bisphenol, 4,4'-cyclohexylidene bis(2 -methylphenol), 4-t, ert-butylphenol,
4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 3,5-xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolac type phenolic resin, 2,2'-thiobis (4,6-dichlorophenol), catechol, resorcinol, hydroquinone,
Pyrogallol, phloroglycin, phloroglycin carboxylic acid, 4-ter7-octylcatechol, 2.2
'-Methylenebis(4-chlorophenol), 2,2'
-methylenebis(4-methyl-6-tert-butylphenol), 2゜2'-dihydroxydiphenyl, p-
Ethyl hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl ρ-hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate, 〇-chlorobenzyl p-hydroxybenzoate, P- ρ-methylbenzyl hydroxybenzoate, n-octyl p-hydroxybenzoate, benzoic acid,
■-Hydroxy-2-naphthoic acid, 2-hydroxy-6
-naphthoic acid, 4-hydroxydiphenylsulfone, 4
-Hydroxy-4'-chlorodiphenyl sulfone, bis(4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, tartaric acid, oxalic acid, maleic acid,
Citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, thiourea derivatives, 4-hydroxythiophenol derivatives, etc.

In the present invention, in order to bind and support the leuco dye, color developer, and zinc compound on a support.

Various conventional binders can be used as appropriate, and specific examples thereof include the following.

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate,
Polyvinylpyrrolidone, acrylic amide/acrylic ester copolymer, acrylic amide/acrylic ester/methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali In addition to water-soluble polymers such as salt, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer , polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/
Latex such as butadiene/acrylic copolymer.

In addition, in the present invention, in addition to the leuco dye and color developer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, surfactants, thermofusible substances ( or lubricant), etc. can be used in combination. In this case, fillers include, for example, calcium carbonate, silica, titanium oxide, aluminum hydroxide, barium sulfate, clay, talc, surface-treated inorganic fine powders such as calcium and silica, urea-formalin resin, styrene, etc. /
Examples of thermofusible substances include organic fine powders such as methacrylic acid copolymers and polystyrene resins.
For example, in addition to higher fatty acids or their esters, amides, or metal salts, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, 3,4-epoxy-hexahydrophthal Examples include dialkyl acids, higher ketones, and other thermofusible organic compounds having a melting point of about 50 to 200°C.

In the heat-sensitive recording material of the present invention, for example, an undercoat layer coating liquid and a heat-sensitive layer forming coating liquid containing each of the above-mentioned components are mixed with paper,
It is manufactured by coating on a suitable support such as synthetic paper or plastic film and drying, and is applied to various recording fields.

〔effect〕

As described above, the heat-sensitive recording material of the present invention is different from the conventional one by separately containing a metal salt of a salicylic acid compound that acts as a color developer and a zinc compound in the undercoat layer and the heat-sensitive coloring layer. Compared to heat-sensitive recording materials,
It is highly sensitive, does not cause background fogging under high humidity and high temperatures, and is excellent in that it does not discolor when it comes into contact with plasticizers, oils, etc.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that all parts and percentages shown below are based on weight.

Example 1 A mixture consisting of the following compositions was separately ground and dispersed in a sand grinder for 1 to 2 hours to obtain liquid (A), liquid (B), and liquid (C).
) solution and CD) solution were prepared.

[A liquid]

3-N-methyl-3-N-cyclohexylamino-6-
Methyl-7-anilinofluorane 200 parts 10% polyvinyl alcohol aqueous solution 200 parts water
600 copies [B
Liquid] 10% polyvinyl alcohol aqueous solution 200 parts calcium salicylate salt 200 parts water
600
Part [Liquid C] Zinc stearate 200 parts 5%
Methylcellulose aqueous solution 400 parts water
400
Part [Liquid D] Calcium carbonate 200 parts N-
Stearylbenzamide 50 parts 5% methylcellulose aqueous solution 200 parts water
Using 550 parts or more of solutions [A] to [D) obtained as described above.

A heat-sensitive coloring layer coating solution and an undercode layer coating solution having the following compositions were prepared.

Thermosensitive coloring layer coating liquid (1) (A) liquid 100 parts (2) (C
) liquid 300 parts (3) (D) liquid
800 parts Undercoat layer coating liquid (1) CB) liquid 400 parts (2) Styrene-acrylic copolymer 100 parts (organic filler) (3) 40% SBR F/LL John 5o parts (4) Water 450 parts Next , 52
g/rrr (basis weight) of commercially available high-quality paper, the above undercoat layer coating solution was applied with a wire bar so that the dry coating amount was 4.2 g/rrr, and dried to form an undercoat layer, and then applied to the upper layer. The above heat-sensitive coloring layer coating solution was applied with a wire bar to a dry coating amount of 7.4 g/rrf and dried to form a heat-sensitive coloring layer, and then the surface smoothness was 5.
A heat-sensitive recording material of Example 1 of the present invention was prepared by calendering to a temperature of 0.00 to 1000 sec.

Example 2 A heat-sensitive recording material of Example 2 of the present invention was prepared in the same manner as in Example 1 except that zinc hydroxide was used instead of zinc stearate in [liquid C].

Example 3 A heat-sensitive recording material of Example 3 of the present invention was prepared in the same manner as in Example 1 except that barium salicylate was used in place of the calcium salicylate in [liquid B].

Example 4 A heat-sensitive recording material of Example 4 of the present invention was prepared in the same manner as in Example 1 except that 3-phenylsalicylic acid calcium salt was used instead of the salicylic acid calcium salt in [Liquid 8].

Example 5 Instead of liquid (C) of the heat-sensitive color forming layer coating liquid in Example 1, (
A heat-sensitive recording material of Example 5 of the present invention was prepared in the same manner as in Example 1, except that the following liquid [E] was used instead of liquid (B) of the under code layer coating liquid. did.

[E) Liquid zinc xanthate 200 parts 5%
Methylcellulose aqueous solution 400 parts water
400
Comparative Example 1 A heat-sensitive recording material of Comparative Example 1 was prepared in the same manner as in Example 1, except that bisphenol A was used instead of the calcium salicylate in [Liquid B].

Comparative Example 2 A heat-sensitive recording material of Comparative Example 2 was prepared in the same manner as in Example 1 except that liquid [C] was removed from the heat-sensitive coloring layer coating solution.

Comparative Example 3 Except for the undercoat layer of Example 1, [A] liquid: Undercoat layer coating liquid of Example 1: [C] liquid: [D] liquid = 1:
A heat-sensitive coloring layer coating liquid was prepared by mixing and stirring at a ratio of 8:3:8 (weight ratio), and the dry coating amount of this coating liquid was 11.6g1r.
Comparative Example 3 was applied and dried using a wire bar so that
A thermosensitive recording material was created.

The heat-sensitive recording materials described above were tested for color density and color erasability with oil and plasticizer. Table 1 shows the results.
It was shown to. The test method was performed as follows.

1. The colored area was measured using a Macbeth densitometer RD-514 (Furter: W-106) when a heat block with a maximum concentration of 150° C. was brought into contact with a pressure of 2 kg/ai for 2 seconds.

2. Background density: The uncolored area of the obtained sample was measured using a Macbeth densitometer RD-514 (filter: W-106).

3. Oil resistance: After applying cottonseed oil to the printed area whose density was measured, the density was measured after being left at 40° C. for 24 hours.

4. Plasticizer resistance: Plasticizer (DOA
) was allowed to stand for 24 hours at 40°C, and then the concentration was measured.

5. Background fog due to humidity [humidity fog]: The uncolored area of the obtained sample was left for 24 hours at 40° C. and 90% RH, and then the density was measured.

Table-1

Claims (1)

[Claims] (1) In a heat-sensitive recording material comprising an undercoat layer and a heat-sensitive coloring layer laminated in this order on a support, the undercoat layer contains either a metal salt of a salicylic acid compound or a zinc compound. and the other component is contained in the heat-sensitive coloring layer.