JPS63173687A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance the density of a color image and to improve the fastness thereof, by a method wherein a recording layer containing a methine compound, a benzoquinone derivative, and an acid compound, which are shown by specific general formulas, is formed on a substrate. CONSTITUTION:A water coating liquid is prepared by compounding a methine compound shown by formula I (A, B, X, Y represent phenyl, naphthyl, and indole), a benzoquinone derivative shown by formula II (R1-R4 represent H, halogen, acyl, etc.), and an acid compound shown by formula III (R5-R9 represent H, halogen, alkyl, etc.) or IV (R10-R12 represent H, halogen, alkyl, etc.). This coating liquid is applied on a substrate such as paper and film; in this manner, a thermal color-forming layer is formed and then a thermal recording material is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material that is prevented from being contaminated by various solvents and has improved stability.

Heat-sensitive recording paper that uses a coloring reaction caused by thermal contact between basic dyes such as phthalide or fluorane and acidic phenolic compounds such as bisphenol A or p-oxybenzoic acid esters has been extensively studied and widely used. It has come to be put into practical use. This type of thermal recording paper is
Due to its rapid thermal coloring properties and ease of handling, it is widely used for facsimiles and printers, but colored images based on acid-base reactions are unstable and cannot be used with organic substances, especially organic solvents. Undesirable bleaching or color development can easily occur upon contact with. Specifically, the colored image disappears when it comes into contact with plasticizers, oils and fats, or body fat, and the unprinted name becomes completely colored when it comes into contact with volatile solvents such as alcohol or lower ketones. Improvements have been made, such as considering the composition of paper or the paint used, or introducing a solvent-resistant protective layer, but there is still no prospect of a fundamental solution, and therefore there is no possibility of contact with organic solvents or body fat. This poses a major practical problem in applications where there are many opportunities for frequent contact with people.

On the other hand, heat-sensitive recording materials using the diazo method or the heat-sensitive transfer method, which have been studied in recent years, have excellent stability of colored images, but the stability of the diazo compound to light or the thermal transfer system From the viewpoint of handling and storage, alternative uses are extremely limited.

Based on this current situation, the inventors of the present invention have proposed
No. 107882, No. 58-172787, Patent Application No. 1987
-14273, etc., proposed a copying system based on a new redox coloring method and reported that the colored images produced by such a copying system were extremely stable upon contact with organic solvents. Problems remained in its practical application.

That is, although the stability of the colored image was good, the uncolored surface had a tendency to gradually develop color due to contact with the organic solvent.

The inventors of the present invention have conducted intensive studies on methods for preventing contamination of the fabric (uncolored surface) of such redox coloring thermosensitive recording materials with organic solvents, and have found that a thermosensitive material that has a remarkable effect on the solvent contamination resistance of the background has been found. We discovered a recording material and arrived at the present invention.

That is, in the heat-sensitive recording material of the present invention, (al general formula (
I) (wherein A, B,
When ASB, X, and Y, which represent a
Furthermore, a methine compound represented by (bl general formula (II) ○ (in the formula, R1- R1 each independently represents a hydrogen atom, a halogen atom, an alkoxycarbonyl group, an acyl group or a substituted sulfonyl group) and (C) a benzoquinone derivative represented by the general formula (In) or (IV) (wherein R3-R1 represents a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an acyl group, an aryl group, or an alkoxycarbonyl group (in the formula, R1° to R1
□ each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, or an aralkyl group. X is 0, C
01S SSo, S (h or a lower alkylidene group, m is an integer of O or 1) is a heat-sensitive recording material containing an acidic compound as an essential component.

-S Specific examples of methine compounds represented by formula (I) include α, α1. α”-tetrakis-(4-
methylaminophenyl)-p-xylene, α3 α, α
”, α°-tetrakis(4-ethylaminophenyl)-
p-xylene, α, α, α・.

α°-tetrakis(4-dimethylaminophenyl)-p
-xylene, α, α, αllα9-tetrakis(4-diethylaminophenyl)-p-xylene, α, α, αl
Iα”-tetrakis(3-methoxy-4-ethylaminophenyl)-p-xylene, α, α, α”, α1-tetrakis(3-methoxy-4-methylaminophenyl)-
p-xylene, α, α, α゛, α1-tetrakis (3-
methyl-4-ethylaminophenyl)-p-xylene,
α, α, α°, α”-tetrakis(2-methoxy-4-
dimethylaminophenyl)-p-xylene, α, α, α
′, α゛-tetrakis(2-methyl-4-dimethylaminophenyl)-p-xylene, α, α.

α+lα′-tetrakis(2-methyl-4-dimethylaminophenyl)-p-xylene, α, α, α″, α″-
Tetrakis(4-benzylaminophenyl)-p-xylene, α, α, α1. α゛-tetrakis(4-methylbenzylaminophenyl)-p-xylene, α,α,α゛,α”-tetrakis(4-ethylbenzylaminophenyl)-p-xylene, α,α,α9.α1-tetrakis (4-Methylphenylaminophenyl)-p-xylene, α.

α, α”, α9-tetrakis (3,6-cymethyl-4-
Dimethylaminophenyl>-p-xylene, α, α, α
', α''-tetrakis(3-chloro-4-benzylaminophenyl)-p-xylene, α.

α, αIlα1-tetrakis (3,6-simethoxy4
-dimethylaminophenyl)-p-xylene, α, α,
α゛,α”-tetrakis(3,6-simethoxy-4-benzylaminophenyl)-p-xylene, α,α,αゝ,α°-tetrakis(4-methylamino-naphthyl-1
)-p-xylene, α, α, α゛, α1-. α1-tetrakistylaminonaphthyl-1)-p-xylene, α,
α, α°, α゛-tetrakis(3-methoxy-4-methylaminonaphthyl-1)-p-xylene, α, α, α″
, α゛-tetrakis(4-methoxyphenyl)-p-xylene, α1 α, α゛, α゛-tetrakis(4-ethoxyphenyl)-p-xylene, α, α, α°, α゛-
Tetrakis(I-ethyl-2-methylindole-3-
yl)-p-xylene, α, α.

α”, α”-tetrakis-1-butyl-2-methylindol-3-yl)-p-xylene, α, αゝ-bis(4
-dimethylaminophenyl)-α.

α”-bis(4-methoxyphenyl)-p-xylene,
α,α゛-bis(3-ethyl-4-ethylaminophenyl)-α,α′-bis(4-methoxyphenyl)-p-
Examples include xylene, α, α1-bis(4-dimethylaminophenyl)α, α°-bis(I-ethyl-2-methylindol-3-yl)-p-xylene, but are of course not limited to these. It never happens.

Specific examples of the benzoquinone m8 body represented by the general formula (I hexylcarbonyl-1,4-
Benzoquinone, 2,5-dibenzoyl-1,4-benzoquinone, 2,5-dibenzoyl-3-fromo1,4-
Benzoquinone, 2,5-dibenzoyl-3,6-dichloro-1,4-benzoquinone, 3-benzoyl-1,4-
Benzoquinone, 3,6-diP-)luenesulfonyl-
Examples include 2,5-jethoxycarbonyl-1,4-benzoquinone. Among these benzoquinone derivatives, 2,5-dibenzoyl-1,4-benzoquinone is particularly useful as a stable and less oil-soluble color developer.

Furthermore, in the present invention, the general formula ('II[
) or (IV) is used.

In the present invention, the acidic compound used as an essential component together with the methine compound and the benzoquinone derivative is represented by the general formula (I [[) or (IV)], and specific compounds include, for example, 2.4-Dicumylphenol, 2-phenylphenol, 4-phenylphenol, 4-tert-butylphenol, 2-chloro-4-cumylphenol, 2-chloro-4,6-dicumylphenol, 4-benzylphenol , 2-bromo-4,6-dicumylphenol, 2-methyl-4-(
I-phenylethyl)phenol, 2-methyl-4-cumylphenol, 2-methyl-4,6-dicumylphenol, 2-methyl-4-tert-butylphenol,
Examples include 4"-hydroxyacetophenone, 4-hydroxybenzophenone, methyl-p-hydroxybenzoate, benzyl-p-hydroxybenzoate, etc.
On the other hand, the compound represented by -i formula (IV) is 2
．． 2'-dihydroxybiphenyl, 4.4'-dihydroxybiphenyl, 2.2°-dihydroxy-5,5'-
Dicumyl biphenyl, bisenol A, bisenol C
, bisenol S, bis(2-hydroxy-5-cumylphenyl) sulfide, bis(2-hydroxy-3-chloro-5-methylphenyl) sulfide, bis(2-hydroxy-5-(l-phenylethyl)phenyl) sulfide , bis(2-hydroxy-5-cumylphenyl)
Examples include sulfone, 4,4'-dihydroxydiphenyl ether, etc. Among these, those suitable for the properties required for the heat-sensitive recording material are arbitrarily selected and used.

By using such an acidic compound, the effect of significantly improving the color density and color fastness can be seen.

The heat-sensitive recording material of the present invention comprises a methine compound of general formula (I), a benzoquinone derivative of general formula (n), a benzoquinone derivative of general formula (III)
) or (IV), colorless organic or inorganic pigments are generally mixed and used in order to improve paper properties, writing properties, and matching properties to thermal heads.

As such pigments, a large number of substances have been proposed and are known, and can be selected and used as appropriate, but suitable pigments in the present invention include light or heavy calcium carbonate, magnesium carbonate, and water. Examples include neutral or weakly basic pigments such as aluminum oxide, zinc oxide, polystyrene resin, and finely divided urea formaldehyde resin. Pigments that are themselves acidic, such as certain types of kaolin,
Acid clay and the like often tend to stain the surface of heat-sensitive recording materials, so care must be taken when handling them.

The heat-sensitive recording material of the present invention is produced by adding various coloring sensitivity improvers, lubricants, waterproofing agents, surfactants, etc. in addition to the above-mentioned components, as well as a binder component.
Alternatively, it is manufactured by coating and drying it on a support such as a film.

Binders used with the various ingredients listed above include:
Generally polyvinyl alcohol, methyl cellulose,
Water-soluble polymer binders such as hydroxyethyl cellulose and starch, or synthetic resin binders such as acrylic emulsion and synthetic rubber latex are used, but polyvinyl alcohol, particularly partially saponified polyvinyl alcohol, is preferably used in the present invention. Partially saponified polyvinyl alcohol, which is cited as the most preferred binder in the present invention, is obtained by partial saponification of polyvinyl acetate, and has a degree of saponification of 60 to 90% and an average degree of polymerization of 500 to 500. 2000, and these are easily available on the market.

Incidentally, preferred quantitative proportions of each component used in carrying out the present invention are as follows.

Methine compound (■) 1 part Benzoquinone derivative (II) 0.3 to 5 parts Acidic compound (I [[) or (IV)] 0.3 to 10 parts Pigment 1 to 50 parts Color sensitivity improver θ to 20 parts Lubricant
1-20 parts binder
1 to 30 parts Waterproofing agent θ
~10 parts Surfactant 0 to 5 parts Prepare an aqueous coating solution having the above composition and apply it to a support such as paper or film using various coating methods so that the dry coating amount is 3 to 20 g/m''. It is dried to obtain a heat-sensitive recording material.

Before creating the above water-based coating liquid, a methine compound,
The benzoquinone derivative and the acidic compound are each wet-pulverized into an aqueous suspension in the presence of a protective colloid or a surfactant, and then formed into an aqueous coating solution.

Coating methods include air knife method, knife method,
Specific examples include the blade method and the gravure method, and the aqueous coating liquid has a viscosity and solid content suitable for each coating method.

The heat-sensitive recording material of the present invention having such a structure produces a deep and robust colored image derived from the irreversible reaction between the methine dye and the benzoquinone derivative, and has significantly improved solvent resistance stability of the uncolored state. As a result, applications in areas where there is a high possibility of contact with solvents, such as food barcode P
OS label (in this case plasticizer in the wrap film,
The heat-sensitive recording material of the present invention is extremely suitable for applications such as those in which there is a lot of contact with oils and fats such as meat, fish, etc.), train tickets, and commuter passes that require long-term color image stability. Unlike the thermal recording paper that has been used for this purpose, there is no need for a complicated layer structure with an undercoat and overcoat layer to achieve solvent resistance stability, so production is efficient and inexpensive. It is possible to do it.

The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

First, a method for preparing a heat-sensitive paint and an evaluation method will be shown.

(A) Preparation of water-based paint and heat-sensitive recording paper Parts by weight Methine compound (I0χ aqueous dispersion) 8.5 Benzoquinone derivative (2 oz aqueous dispersion) 7.0 Acidic compound (
) 7.0 β-naphthyl benzoate (same as above - color development sensitivity improver) 5.0 Pigment (50χ aqueous dispersion) 42.5
Binder (I0χ aqueous dispersion) 11.5
water
8.5 Prepare a well-mixed water-based paint in the proportions above.

Note that the methine compound, benzoquinone derivative, acidic compound, and zinc stearate are used as an aqueous dispersion obtained by wet pulverization in the presence of a small amount of a protective colloid substance.

The water-based paint thus obtained was coated on high-quality paper with a basis weight of 50 g/m'' using a Mayer bar coater to give a dry coating amount of 6.0 g.
/m'' and dried, followed by surface smoothing treatment using a supercalender to obtain heat-sensitive recording paper.

(B) Color development test method The heat-sensitive recording paper prepared above was colored using a thermal printer (applied voltage 20 v, current application time 1.4+*5 ec), and the colored area was measured and displayed using a Macbeth densitometer (Visible Filter).

(C) Plasticizer resistance coloring test method Using dioctyl phthalate as the core material, melamine
Coated paper plasticizer test paper) in which microcapsules prepared by the formalin In-9itu polymerization method were coated on high-quality paper at a dry coating amount of 5 g/m'', and microcapsules of each example or comparative example. The coated surfaces of thermal recording paper are superimposed and subjected to super calender treatment (linear pressure 100 kg).
/cu+) Destroy the microcapsules and add 40
After being left at °C for 24 hours, the reflectance (xl) of the coated surface was determined using a Hunter colorimeter (using an amber filter), and using the reflectance (X, ) before the test, the effect of contact with dioctyl phthalate was determined. Find the color development rate.

X, -X.

Color development rate (K) -X100(χ) a The higher the color development rate, the greater the background color development (contamination) due to contact with acidic solvents such as plasticizers.

Comparative Example-1 In the above aqueous coating liquid composition, as a methine compound, α
1 α-bis(4-dimethylaminophenyl)toluene [leucomalachite green], 2,5-dibenzoyl-1,4-benzoquinone as a benzoquinone derivative,
Bis(2-hydroxy-5-cumylphenyl) sulfone was used as the acidic compound, and polyvinyl alcohol having a degree of saponification of 100[chi] and a viscosity of 10% aqueous solution of 1360 cps was used as the binder.

When the pressure-sensitive recording paper of this example obtained using the above water-based coating liquid was colored with a thermal printer, a dark green colored image was obtained (Macbeth density value 1.08), as a result of the plasticizer resistance test. was 64%, and a marked tendency for skin color development was observed.

Example-1 Comparative Example-1 except that the same amount of α, α, α′, α゛-tetrakis(4′=dimethylaminophenyl)-p-xylene was used instead of leucomalachite green as the methine compound. A thermosensitive recording paper was obtained in the same manner as above.

The heat-sensitive recording paper of this example was able to obtain a dark green colored image (Macbeth density value 1°10) as in Comparative Example-1.
The result of the plasticizer resistance test was 4%, indicating a significant solvent resistance effect.

Examples 2 to 4 The methine compound of Example-1 was adjusted to α, α, α°, respectively.
, α°-tetrakis(3-methyl-4-methylaminophenyl>-p-xylene, α, α, α+lα1-tetrakis(4-dimethylaminophenyl)-p-xylene,
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that α, α, α゛, α°-tetrakis(2-methyl-4-dimethylaminophenyl>-p-xylene) was used.

Both thermosensitive recording papers developed a dark green color.

The color density and plasticizer resistance test values were as follows.

Macbeth value Plasticizer resistance example-21,158! 3 1.18 10χ 4 1.12 3χ Comparative Example-2 From Example-1, the acidic compound bis(2-hydroxy-5-
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that cumyl phenyl sulfone was omitted.

As a result of the color development test, the thermal paper of this example did not have a practically sufficient color density (Macbeth density value, 0.76).

Comparative Example-3 In Comparative Example-1, instead of α,α-bis(4-dimethylaminophenyl)toluene, α,α-bis(I-ethyl-2
A thermosensitive recording paper was prepared in the same manner as in Comparative Example 1 except that methylindol-3-yl)toluene was used.

When this thermal paper was colored with a thermal printer, a deep red colored image was obtained (Macbeth density value, 1.01).

The result of the plasticizer resistance test was 39%, and the entire surface turned red.

Example-5 In Example-1, α, α, α'', α°-tetrakis (4-
Dimethylaminophenyl>-p-xylene, α
, α, α゛, αゝ-Tetrakis(I-ethyl-2-methylindol-3-yl>-p-xylene) A thermosensitive recording paper was prepared in the same manner as in Example 1 except that p-xylene was used.

The thermosensitive recording paper of this example provided sufficient red coloring density (Macbeth density value 1.06) and exhibited extremely good plasticizer resistance (3χ).

As is clear from the above Examples and Comparative Examples, the heat-sensitive recording material of the present invention containing a methine compound, a benzoquinone derivative, and an acidic compound as essential components develops a deep color when heated and provides a robust colored image. In addition, the colored areas do not fade due to contact with solvents, and the non-colored areas are heat-sensitive with a significantly reduced tendency to stain due to solvents such as phthalate esters, adipate esters, body fat, or animal and vegetable oils. It is a recording material.

The heat-sensitive recording material of the present application is used in applications where there is a high possibility of contact with such solvents, or applications where long-term stability of colored images is required, such as POS barcode labels for fresh foods, commuter passes, and train tickets. It is suitable for applications such as

Claims (1)

[Claims] 1) (a) General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, A, B, X, and Y each represent phenyl which may have a substituent. group, naphthyl group or indole-3-
Indicates an yl group. When each of A, B, It may have an alkyl group, lower alkoxy group, halogen atom or amino group. ), (b) General formula (II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, R_1 to R_4 each independently represent a hydrogen atom, a halogen atom, an alkoxycarbonyl group, acyl group or substituted sulfonyl group) and (c) general formula (III) or (IV) ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (III) (In the formula, R_5 to R_9 are respectively (Independently represents a hydrogen atom, halogen atom, alkyl group, aralkyl group, acyl group, aryl group, or alkoxycarbonyl group.) ▲Mathematical formulas, chemical formulas, tables, etc.▼(IV) (In the formula, R_1_0 to R_1_2 each independently represents a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, or an aryl group. X represents O, CO, S, SO, SO_2 or a lower alkylidene group, and m represents an integer of 0 or 1.) A heat-sensitive recording material containing an acidic compound as an essential component.