JPS61164882A - Thermal recording material - Google Patents

Abstract

PURPOSE:To ensure a high sensitivity, to prevent decoloration from occurring on contact with a plasticizer, an oil or the like and to prevent ground fogging from occurring under hot and humid conditions, by a method wherein a 2,3- dihydroxynaphthalene compound is used jointly as a color developer, and one of said compound and a metallic compound is incorporated in an undercoat layer, while the other is incorporated in a thermal color forming layer. CONSTITUTION:One of a 2,3-dihydroxylnaphthalene compound and a metallic compound is incorporated in an undercost 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 compound may be, for example, an oxide of iron, copper, zinc or the like, a hydroxide of such a metal, or a salt of such a metal with an organic acid such as benzoic acid. The naphthalene compound as the color developer is used in an amount of not less than 20wt% based on the total weight of color developers, preferably, not less than 50wt%. The metallic compound is used in an amount of 0.2-5.0pt.wt. per 1pt.wt. of the naphthalene 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 coloring layer containing a thermochromic composition as a main component.
A colored image can be obtained by heating with a strobe lamp or the like. Compared to other recording materials, this type of recording material
1 due to its advantages such as 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. Thermochromic compositions used in such heat-sensitive recording materials generally consist of a coloring agent and a color developer that causes the coloring agent to develop a specific color under heat.
As the color former, for example, a colorless or light-colored leuco dye having a lactone, lactam or spiropyran ring is used, and as a color developer, an organic acid or a phenolic substance is conventionally used. A recording material made of a combination of a color former and a color developer has the advantage that the resulting image has a particularly clear color tone, has a high background whiteness, and has excellent weather resistance. Widely used.

Conventionally, bisphenol A and P-hydroxybenzoic acid esters have been used as color developers for leuco dyes, but these phenols have a high monochromatic density but lack the stability of colored images, so they cannot be used naturally. 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. JP-A-59-38091 is used as a color developer that provides images with good stability.
As seen in the publication, it has been proposed to use aluminum chloride as at least a part of the color developer, but in this case, it is necessary to use a highly reliable thermal paper that hardly discolors the image even when it comes into contact with oils and fats. However, there is a drawback that the skin concentration is high due to the formation of liquid fogging at the time the heat-sensitive 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, it has high sensitivity, does not fog due to humidity, and does not discolor when it comes into contact with plasticizers, oil, etc. Our objective is to provide a heat-sensitive recording material that is unique.

〔composition〕

According to the present invention, in a heat-sensitive recording material comprising an undercoat layer and a heat-sensitive coloring layer laminated in that order on a support,
A heat-sensitive recording material, characterized in that one of a 2,3-dihydroxynaphthalene compound and a metal compound is contained in the undercoat layer, and the other component is contained in the heat-sensitive coloring layer.

The 2,3-dihydroxynaphthalene compound used in the present invention is a compound having a hydroxy group at the 2,3-position of the naphthalene ring, and a substituent other than the hydroxy group can also be bonded to the naphthalene ring. In the present invention, it is preferable to use a compound represented by the first-order general formula.

[In the formula, R is a hydrogen atom, or an alkyl, aryl, alkoxy, aralkyl, sulfonic acid group, sulfonic acid metal base (alkali metal salt, alkaline earth metal salt, aluminum salt, etc.), sulfonic acid amide group, halogen, etc. represents a substituent. n is an integer from 1 to 4, and if n is multiple,
Each R may be the same or different. ] The 2,3-dihydroxynaphthalene compound used in the present invention acts as a color developer for leuco dye, and when used in combination with a metal compound, bisphenol A
Compared to conventional color developers, it has the advantage that the color image area is more stable and the image does not fade even when it comes into contact with plasticizers, oils, etc. Furthermore, the above 2,3-
It has been found that moisture fog resistance is significantly improved by containing either a dihydroxynaphthalene compound or a metal compound in the undercoat layer provided adjacent to the heat-sensitive coloring layer.

Specific examples of the 2,3-dihydroxynaphthalene compounds used in the present invention include the following.

Specific examples of the metal compounds used in the present invention include transition metals such as iron, copper, and zinc, as well as oxides, hydroxides, and fluorides of various metals such as aluminum, tin, and lead, or compounds of these metals. and benzoic acid, ρ-jert butylbenzoic acid, salicylic acid, stearic acid, myristic acid,
Lauric acid, benzoin, acetylacetonate, p-
Examples include salts with organic acids such as toluenesulfonic acid, octylsulfonic acid, p-tert-butylsulfonic acid, dimethylglyoxime, and xanthic acid, but are not necessarily limited to these.

As the color developer used in the present invention, the above-mentioned 2 and 3
- In addition to the dihydroxynaphthalene compound, a color developer consisting of a conventionally known phenolic substance, an inorganic or organic acidic substance, or a derivative thereof can also be used in combination, if necessary. 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 a dihydroxynaphthalene compound accounts for 20% by weight or more, preferably 50% by weight or more of the total color developer.

Further, the metal compound used in combination with the 2,3-dihydroxynaphthalene compound is used in an amount of 0.2 to 5.0 parts by weight per 1 part by weight of the 2,3-dihydroxynaphthalene compound.

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-Bis(P-dibutylaminophenyl)-phthalide.

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

3.3-bis(p-dibutylaminophenyl)phthalide.

3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7-dimethylfluorane, 3
-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6
-Methyl-7-chlorofluorane.

3-(N-p-tolyl-N-dithylamino)-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'- Hydroxy-41-dimethylaminophenyl)-3-(2'-methoxy-51-chlorophenyl)phthalide, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5' -nitrophenyl) phthalide.

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

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

3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-ρ-chlorophenyl) Methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-ρ-toluidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino -7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p-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(l-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-(p-dimethylaminophenyl)-3-(p-dibenzylaminophenyl) phthalide.

3-(N-ethyl-Nn-amyl)amino-6-methyl-7-anilinofluorane and the like.

In the present invention, various electron-accepting substances that react with the leuco dye to develop color when heated can be used as the color developer that can be used in combination with the color developer made of a 2,3-dihydroxynaphthalene compound. Specific examples thereof include phenolic substances, organic or inorganic acidic substances, and esters and salts thereof as shown below.

gallic acid, salicylic acid, 3-isoprobylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di-t,er
t-Butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4'-isopropylidene diphenol, 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-SerF:,
-butylphenol), 4.4'-5ec-butylidene diphenol, 4.4'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis(2-
methylphenol), 4-tart-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, phloroglycine, phloroglycin carboxylic acid, 4-t, ert-octylcatechol, 2
, 2'-methylenebis(4-chlorophenol), 2.
2'-methylenebis(4-methyl-6-tert-butylphenol).

2.2'-dihydroxydiphenyl, ethyl P-hydroxybenzoate, propyl P-hydroxybenzoate, P-
Butyl hydroxybenzoate, benzyl P-hydroxybenzoate, p-chlorobenzyl P-hydroxybenzoate, 〇-chlorobenzyl P-hydroxybenzoate, P-
ρ-Methylbenzyl hydroxybenzoate, n-octyl P-hydroxybenzoate, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-6-naphthoic acid Zinc acid, 4-hydroxydiphenylsulfone, 4-hydroxy-4'-chlorodiphenylsulfone, bis(4-hydroxyphenyl)sulfide, 2-hydroxy-P-toluic acid, zinc 3,5-diterj-butylsalicylate, 3 , 5-di-tert-butyltin salicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, in the present invention, the leuco dye, color developer and metal compound are contained. In order to bond and support the undercoat layer and thermosensitive coloring layer on the support, various commonly used 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 In addition to water-soluble polymers such as alkali salts, 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/butadiene/acrylic copolymer, etc.

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, barium sulfate, clay, talc, inorganic fine powders such as surface-treated calcium and silica, urea-formalin resin, styrene/methacrylic acid copolymer, Organic fine powder such as polystyrene resin can be mentioned, and examples of thermofusible substances include higher fatty acids or their esters, amides, various waxes, condensates of aromatic carboxylic acids and amines, Examples include benzoic acid phenyl ester, higher linear glycols, dialkyl 3,4-epoxy-hexahydrophthalate, higher ketones, and other thermofusible organic compounds with melting points of about 50 to 200°C. .

The heat-sensitive recording material of the present invention can be prepared by, for example, applying an undercoat layer coating liquid and a heat-sensitive layer forming coating liquid containing each of the above-mentioned components to 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〕

The heat-sensitive recording material of the present invention uses a 2,3-dihydroxynaphthalene compound as a color developer together with a metal compound, and by making one of them exist in the undercoat layer and the other in the heat-sensitive coloring layer, It is highly sensitive and does not fade due to contact with plasticizers, oils, etc., and also has excellent properties that do not cause background fogging under high temperature and high humidity conditions.

〔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 Mixtures consisting of the following compositions were separately mixed using a sand glider.
After grinding and dispersing for 1 to 2 hours, (A) liquid, [B] liquid, (C)
A liquid and a liquid (D) were prepared.

(A) Liquid 3-N-methyl-3-N-cyclohexylamino-6-
Methyl-7-anilinofluorane 200 parts 10% polyvinyl alcohol aqueous solution 200 II water
6oo〃
(B) Liquid 2.3-dihydroxynaphthalene 200 parts 1
0% polyvinyl alcohol aqueous solution 20011 water
6
00 [C] Liquid aluminum stearate (trivalent) 200 parts 5% methylcellulose aqueous solution 40011 Water
400//(D) Liquid calcium carbonate 200 parts N-
Stearylbenzamide 5Qn 5% methylcellulose aqueous solution 200 parts water
Using the liquids [A] to (D) obtained as described above, a heat-sensitive color forming layer coating liquid and an undercoat layer coating liquid having the following compositions were prepared.

Thermosensitive coloring layer coating liquid (1) (A) liquid 100 parts (2)
(C) Liquid 300 parts (3) CD
) liquid 800 parts Undercoat layer coating liquid (1) CB) liquid 900 parts (2)
40% SBR emulsion 100 parts then 52g
/rrr (basis weight) of commercially available high-quality paper with a dry coating amount of 2.4 g/n? After coating with a wire bar and drying to form an undercoat layer,
On top of that, a dry coating amount of heat-sensitive coloring layer coating liquid is 7.4g/r.
rr coating with a wire bar and drying to form a heat-sensitive coloring layer, then the surface smoothness is 500 to 10.
A heat-sensitive recording material of Example 1 of the present invention was prepared by calendering to a temperature of 0.00 sec.

Example 2 Same procedure as in Example 1 except that liquid (C) was used instead of liquid CB) in the undercoat layer coating liquid, and liquid (B) was used in place of liquid [C) in the heat-sensitive coloring layer coating liquid. Example 2 of the present invention
A thermosensitive recording material was created.

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 2,3-dihydroxynaphthalene was used as the 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 zinc stearate was used instead of aluminum stearate (trivalent) in [liquid C].

Example 5 A heat-sensitive recording material of Example 5 of the present invention was prepared in the same manner as in Example 1 except that a 40% styrene-acrylic copolymer emulsion was used in place of the 40% SBR emulsion of the CD solution in Example 1.

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 2,3-dihydroxynaphthalene in liquid (B).

Comparative Example 2 The ratio of (A) liquid: [C] liquid; [D] liquid in Example 1 was l:o.
A heat-sensitive recording material of Comparative Example 2 was prepared in the same manner except that the weight ratio was changed to: :8 (weight ratio).

Comparative Example 3 Except for the undercoat layer in Example 1, (A) liquid:
Undercoat layer coating liquid of Example 1: [C] liquid: [D] liquid = 1:4:3:8 (weight ratio) was mixed and stirred to prepare a heat-sensitive coloring layer coating liquid. The dry application amount is 9,8
Apply it with a wire bar so that it is g/rd, dry it,
A heat-sensitive recording material of Comparative Example 3 was prepared.

The above heat-sensitive recording sheets were tested for color density and decolorizability with oil and plasticizer. The results are shown in Table-1. The test method was performed as follows.

(1) Maximum concentration: 2 kg of 150℃ heat block
/Ci pressure for 1 second and the colored area was measured using a Macbeth densitometer RD-514 (filter 1-106).

(2) Background density...The uncolored area of the obtained sample was measured using a Macbeth densitometer RD-514 (7A) Lt vine: V-
106).

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

(4) Plasticizer resistance: After a plasticizer (DOA) was attached to the printed area whose density was measured, the density was measured after being left at 40° C. for 24 hours.

(5) Background fog due to humidity [humidity fog]: The uncolored area of the obtained sample was heated at 40°C and 90% RH for 2 hours.
After standing for 4 hours, the concentration was measured.

Claims (1)

[Claims] (1) In a heat-sensitive recording material formed by laminating an undercoat layer and a heat-sensitive coloring layer in that order on a support, a 2,3-
A heat-sensitive recording material, characterized in that the undercoat layer contains one of a dihydroxynaphthalene compound and a metal compound, and the other component is contained in the heat-sensitive coloring layer.