JPS6235881A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material having sufficient color developing density and color forming sensitivity, suitable for high-speed recording and having high ground whiteness and practicality, by using a specified zinc complex as a color developer and using at least one selected from specified naphthalene compounds as an auxiliary component, in a thermal recording material provided with a thermal color forming layer comprising a leuco dye and a color developer on a base. CONSTITUTION:A zinc complex of formula (I) is used as a color developer and at least one selected from naphthalene compounds of general formula (II) is used as an auxiliary component, in a thermal recording material employing a color forming reaction between a leuco dye and a color developer. In formula (I), R is an organic ligand capable of forming a complex by combining with zinc ion through a hetero-atom, k is 2 or 4, and X is SCN or halogen. In formula (II), R is alkyl, alkoxyl, halogen, subst. or unsubst. aralkyl or aryl, and an is 1-8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording material, and particularly to a heat-sensitive recording material that is excellent in color development and other recording properties, and has good image stability.

[Prior art]

General heat-sensitive recording materials are coated on a support such as paper or film, and contain a colorless or light-colored dye such as a leuco dye as a color former, and a phenolic compound (particularly bisphenol A) as a color developer to make the color develop when heated. A heat-sensitive color-forming layer in which a binder, filler, sensitivity improver, lubricant, and other auxiliary agents are further dispersed in a color-forming system consisting of an acidic substance such as an organic acid. Kosho 45-14
No. 039 and Japanese Patent Application Laid-Open No. 48-27736, it has been widely put into practical use. This type of thermal recording sheet produces a colored image through an instantaneous chemical reaction between a coloring agent and a color developer during heating (a thermal printer or facsimile machine with a built-in thermal head is used for heating). because there is,
Compared to other recording materials, records can be obtained in a short time using relatively simple equipment without complicated processing such as development and fixing, there is less noise generation and environmental pollution, and the cost is low. Due to the advantages of
It is useful as a recording material for various information and measuring instruments such as medical measuring instruments.

However, in the case of this type of leuco-based heat-sensitive recording material,
The disadvantage is that the stability of the recorded image is poor and, for example, the recorded image is easily discolored when it comes into contact with oils or plasticizers such as dioctyl phthalate contained in plastic films.

Conventionally, in order to improve the stability of recorded images, for example, a thermosensitive coloring layer containing a large amount of water-resistant and chemical-resistant resin, a thermosensitive coloring layer containing a resin that hardens by heat or light,
Alternatively, a method has been proposed in which a resin protective layer is formed on the surface to protect the heat-sensitive coloring layer from the effects of chemicals and water, but this method complicates processing, increases costs, and also reduces thermal responsiveness. It has the problem of being stored away.

In order to solve this problem, the present inventor made extensive efforts and first used an antipyrine complex of a zinc complex represented by the formula (1) below as a color developer for leuco dyes. It has been found that it is possible to obtain a heat-sensitive recording material with extremely high image stability, which does not develop color in the background area or decolorize in the colored area even when in contact with an agent or the like.

On the other hand, in recent years, along with the development of society, there has been an increasing demand for higher speed and higher density recording. For this reason, there is a strong desire not only to increase the speed of the recording apparatus itself, but also to develop recording materials that can handle this. Conventionally, in order to make heat-sensitive recording materials suitable for high-speed recording, for example,
No. 39139, JP-A-53-26139, JP-A-53
As described in JP-A-5636, JP-A-53-11036, etc., various waxes, fatty acid amides, alkylated biphenyls, substituted biphenylalkanes, coumarins, diphenylamines, etc., are used in the heat-sensitive coloring layer. There is a method of adding a heat-melting substance as a sensitizer (or melting point depressant). However, when these methods are applied to heat-sensitive recording materials that use zinc complexes as color developers, they are still insufficient in terms of color development density, color development sensitivity, background whiteness, and water resistance of images. It's hard to say.

〔the purpose〕

The purpose of the present invention is to achieve a color density of 1 and a sufficient color sensitivity.

Suitable for high-speed recording, and has high background whiteness.

In addition, it is an extremely practical thermosensitive recording material that does not develop color in the background or decolorize the colored area even when it comes into contact with oils or plasticizers, and does not reduce image density even when it comes in contact with water, such as when immersed in water. Our goal is to provide the following.

【composition〕

According to the present invention, in a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and its color developer, a zinc complex represented by the following formula (1) is used as the color developer, and
There is provided a heat-sensitive recording material characterized in that at least one kind selected from naphthalene compounds represented by the following general formula (II) is used as an auxiliary component.

General formula (1) %Formula %(1) (In the formula, R represents an organic ligand capable of bonding with a zinc ion to form a complex via a hetero atom, k represents 2 or 4, and X represents SCN or a halogen atom), and at least one kind selected from naphthalene compounds represented by general formula (II) as an auxiliary component.

General formula (If) (wherein R represents an alkyl group, an alkoxy group, a halogen atom, a substituted or unsubstituted aralkyl group, or an aryl group, and n represents 1 to 8) used as a color developer in the present invention The zinc complex represented by the general formula (1) and the naphthalene compound represented by the general formula (II) used together as an auxiliary component should have a melting point of 40 to 150°C from the viewpoint of storage stability and sensitivity as a heat-sensitive recording material. Preferably, especially 5
Preferably, the temperature is 0 to 120°C.

Specific examples of the zinc complex of the present invention are shown below, but the present invention is not limited thereto.

Further, specific examples of the naphthalene compound of the present invention are shown below, but the present invention is not limited thereto.

Compound Structure Formula The leuco dyes used in the present invention can be applied singly or in a mixture of two or more types, but such leuco dyes include:
Any dye that has been applied to this type of heat-sensitive material may be used. For example, leuco compounds of dyes such as triphenylmethane, fluoran, phenothiazine, auramine, and spiropyran 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-dibutylaminophenyl, 3.3-bis(P-dimethylaminophenyl)-6-chlorophthalide, 3.3-bis(P-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6- Chlorfluorane, 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-ethylamino)-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-(0-chloroanilino)fluoran, 3-dibutylamino-7-(0-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-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-ditrophenyl)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)fluoran.

3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-P-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 etc.

In the present invention, in order to bind and support the leuco dye, color developer and auxiliary components on the support, various conventional binders can be used as appropriate, such as polyvinyl alcohol, starch and its derivatives, methoxy Cellulose derivatives such as cellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and 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 salt, polyacrylamide, sodium alginate, gelatin, casein, and other water-soluble polymers, as well as polyvinyl acetate, polyurethane, styrene/butadiene. Copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/
Latex such as vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butadiene/acrylic copolymer, etc. can be used.

In addition, in the present invention, in addition to the leuco dye, color developer, and auxiliary components, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, surfactants, A thermofusible substance (or lubricant), etc. can be used in combination. In this case, fillers include 1, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium and silica. , urea-formalin resin, styrene/methacrylic acid copolymer, polystyrene resin, and other organic fine powders.

The heat-sensitive recording material of the present invention is produced, for example, by applying a coating liquid for forming a heat-sensitive layer containing the above-mentioned components onto a suitable support such as paper, synthetic paper, or plastic film, and drying the coated liquid. In this case, the amounts of the leuco dye, color developer, and color development sensitivity enhancer used are 5 to 40% by weight and 20% by weight, respectively.
-60% by weight, 20-60% by weight is suitable.

〔effect〕

The heat-sensitive recording material of the present invention has improved sensitivity, is suitable for high-speed recording, has a high degree of whiteness of the background, and is also resistant to coloring of the background and coloring of the colored area when it comes into contact with oils and plasticizers. It is highly practical as it does not fade and the image density does not decrease even when it comes into contact with water, such as when immersed in water.

These effects can be obtained by using the zinc complex represented by the formula (1) in combination with a specific naphthalene compound.

〔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.

Further, the antipyrine complex of zinc thiocyanate (compound No. 1) used in the Examples described later was synthesized in the following manner.

14.4 g of zinc sulfate (ZnSO4.IH20) and 29.2 g of potassium thiocyanate were dissolved in 200 mQ of water. Separately, a solution of 8.8 g of antipyrine dissolved in 200 mΩ of water was prepared, and when the solution was added dropwise to the above solution while stirring, a white precipitate was immediately generated. This precipitate was filtered, washed with water, dried, and the obtained white powder was recrystallized from a mixed solvent of water and ethanol to obtain 24.2 g of white crystals of an antipyrine complex of zinc thiocyanate with a melting point of 118 to 120°C. .

Example 1 The following solutions (A) to (D) were prepared by separately pulverizing and dispersing mixtures having the following compositions using a magnetic ball mill for two days.

[Liquid A]

3-(N-cyclohexyl-N-methylamino-6-methyl-7-anilite fluorane 20 parts 10% aqueous solution of hydroxyethylcellulose 20 parts water
60 parts [Liquid B] Antipyrine complex of zinc thiocyanate 20 parts 5% aqueous solution of methylcellulose 20 parts water
60 copies [
Solution C] 2-phenylnaphthalene 20 parts (compound of Compound Specific Example No. 019, melting point tOS°C) 5% aqueous solution of methylcellulose 20 parts water
60 copies [D
Liquid] Fine powder of urea-formalin resin 20 parts Methylcellulose 5'% aqueous solution 20 parts Water
60
Parts: 10 parts of liquid A, 30 parts of liquid B, 30 parts of liquid C, 20 parts of liquid D.
part and 20% of isobutylene-maleic anhydride copolymer
After mixing 10 parts of an alkaline aqueous solution to form a thermosensitive coloring layer forming solution, this was applied onto high-quality paper with a basis weight of 50 g/rd so that the dry adhesion amount was 4 to 5 g/rd, and was dried to form a thermosensitive coloring layer. Further, the layer surface is calendered so that the surface smoothness becomes 500 to 600 seconds to prepare a heat-sensitive recording material (a
)It was created.

Comparative Example 1 Example 1 except that water was used instead of liquid (C) in Example 1.
A thermosensitive recording material (d) was prepared in the same manner as above.

Comparative Example 2 A heat-sensitive recording material (C) was prepared in the same manner as in Example 1, except that the following liquid (E) was used instead of liquid (C) in Example 1.

(E) Liquid stearamide 20 parts 5% aqueous solution of methylcellulose 20 parts water
60 copies or more of the heat-sensitive recording materials (a) to (C) obtained as described above were printed using a heat-sensitive printing experimental device equipped with a thin-film head manufactured by Matsushita Electronics Co., Ltd., at a head power of 0.45 W/dot and a recording time of 1 line of 20 m5 ec.
/Q, scanning line density 8X3.85 dots/llll1
Under condition 1, the pulse width is 1.6.2.0.2.4 (mse
c) and measure the print density using Macbeth Densitometer RD-5.
14 (filter V-106). The results are shown in Table-1.

Table-1 Next, the thermal recording materials (a) to (c) were printed using a thermal gradient tester (manufactured by Toyo Seiki) at a pressure of 2 kg, a contact time of 1 second, and a temperature of 150°C. Cut out on all sides,
Layer one layer of polyvinyl chloride film (Polywrap V-300 manufactured by Shin-Etsu Polymer ■) on top of this, and apply a load of 500 g at room temperature.
/d for 24 hours, it was taken out, and the density of the background part and the density of the colored part were measured using a Macbeth densitometer (RD-514) and compared with the density before the test. The results are shown in Table-2.

Table 2 Next, when a thin layer of cottonseed oil was applied to the background and colored areas of similarly printed samples and the samples were stored at room temperature for 24 hours, the background areas of all samples (a) to (c) developed color.

No decolorization of the colored area was observed.

Next, take a sample printed in the same way and place it around the printed part for 4 cr.
100m cut out on all sides and filled with tap water 80ra Q
The samples were immersed in a Q beaker at room temperature for 24 hours, taken out and dried, and the change in density of the colored area was measured. Table the results.
Shown in 3.

Table 3 From the above, the heat-sensitive recording material of the present invention has high sensitivity and white background, does not develop color on the background or decolorize the colored area even when in contact with oils or plasticizers, and can be immersed in water. It can be seen that the image density does not decrease even when it comes in contact with water, making it extremely practical.

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive color forming layer containing leuco dye and a color developer is provided on a support, as the color developer,
General formula (I) (R)kZn(X)_2(I) (In the formula, R represents an organic ligand that can bond with zinc ions via a heteroatom to form a complex, and k represents 2 or 4. and X represents SCN or a halogen atom), and at least one kind selected from naphthalene compounds represented by general formula (II) as an auxiliary component. material. General formula (II) ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ (II) (In the formula, R represents an alkyl group, an alkoxy group, a halogen atom, or a substituted or unsubstituted aralkyl group, or an aryl group, and n is 1 to 8 )