JPS61172792A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material excellent in a color forming property and image stability, by using not only an antipyrine complex of zinc thiocyanate as the coupler of a leuco dye but also a diether compound as an auxiliary component. CONSTITUTION:A solution containing an arbitrary leuco dye, an antipyrine complex of zinc thiocyanate represented by formula I, a diether compound represented by formula II(wherein R is an 1-10C alkylene group or a cycloalkylene group, X and Y is hydrogen, a lower alkyl group, an alkoxy group, an aryloxy group, an aralkyloxy group, an acyl group, an acyloxy group or a halogen atom and may be same or different), a binder and a filler is properly prepared and applied to a support in a dry adhesion amount of about 4-5g/m<2> and dried while calendering is applied to the coating layer so as to adjust surface smoothness to 500-600 sec to obtain a thermal recording material. The use amounts of the leuco dye, the coupler and the auxiliary components are respectively pref. 5-40wt%, 20-60wt%. This thermal recording material has good sensitivity and is suitable for high speed recording and high in background whiteness and further excellent in oil resistance, plasticizer resistance and water resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material that has excellent color development and other recording properties, and also 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 color-forming dye such as a leuco dye as a color-forming agent, and a phenolic compound (especially bisphenol A) as a color-developing agent to cause the dye to develop specific heat color. A heat-sensitive coloring layer in which a binder, a filler, a sensitivity improver, a lubricant, and other auxiliary agents are further dispersed in a coloring system made of an acidic substance such as an organic acid is provided. 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 needle d1 machines.

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 zinc thiocyanate represented by the following formula (1) as a color developer for leuco dyes. It has been found that a heat-sensitive recording material with extremely high image stability, which does not develop color in the background area or decolorize the colored area even when in contact with a plasticizer or the like, can be obtained.

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. Conventional.

In order to make a heat-sensitive recording material suitable for high-speed recording, for example, Japanese Patent Laid-Open No. 53-39139 and Japanese Patent Laid-Open No. 53
-26139, JP-A No. 53-5636, JP-A-53
As described in Publication No. 11036, etc., heat-melting substances with low melting points such as various waxes, fatty acid amides, alkylated biphenyls, substituted biphenylalkanes, coumarins, and diphenylamines are added to the heat-sensitive coloring layer as sensitizers. (or as a melting point depressant). but,
When these methods are applied to heat-sensitive recording materials that use an antipyrine complex of zinc thiocyanate as a color developer,
Color density.

It is difficult to say that these are still satisfactory in terms of color development sensitivity, background whiteness, water resistance of images, etc.

〔the purpose〕

The object of the present invention is to have a color development sensitivity of one color development density, suitable for high-speed recording, high background whiteness, and moreover, a color development in the background area and erasure of the color development area by contact with oils and plasticizers. The object of the present invention is to provide an extremely practical heat-sensitive recording material that is colorless and whose image density does not decrease even when it comes into contact with water, such as when immersed in water.

[Oval]

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, an antipyrine complex of zinc thiocyanate represented by the following formula (1) is used as the color developer, and , there is provided a heat-sensitive recording material characterized in that a diether compound represented by the following general formula (II) is used as an auxiliary component.

General formula (■) of formula (I): (wherein, R is an alkylene group or cycloalkylene group having 1 to 10 carbon atoms, and X and Y are hydrogen, lower alkyl group, alkoxy group, aryloxy group, aralkyl Represents an oxy group, acyl group, acyloxy group or halogen atom,
(X and (2) may be the same or different) The diether compound represented by the general formula (II) used as an auxiliary component in the present invention has a melting point from the viewpoint of storage stability and sensitivity as a heat-sensitive recording material. A temperature of 40 to 150°C is preferable, and a temperature of 50 to 120°C is particularly preferable.

Specific examples of the diether compound of the present invention are shown below, but the present invention is not limited thereto. Furthermore, such diether compounds may be used alone or in combination of two or more.

Compound No. Structural formula % Formula % The leuco dye used in the present invention can be applied alone 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(ρ-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-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-(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, benzoylleucomethylnonblue, 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'-nitrophenyl)phthalide,3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-51-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-p-chlorophenyl)methylaminofluorane.

3-Diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-P-toluidino)-7-(α-phenylethylamino)fluoran.

3-diethylamino-7-(0-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 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 may be added.

For example, fillers, surfactants, thermofusible substances (or lubricants)
etc. can be used together. In this case, the filler is
For example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate,
Examples include inorganic fine powders such as clay, talc, and surface-treated calcium and silica, as well as organic fine powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin.

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 leuco dye, color developer, and color development sensitivity enhancer used are:

5-40% by weight, 20-60% by weight, 20-6 respectively
0% 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 coloration 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 antipyrine complex of zinc thiocyanate represented by the above formula (summer) in combination with a specific diether 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.

Furthermore, the antipyrine complex of zinc thiocyanate used in the Examples described later was synthesized as follows.

14.4 g of zinc sulfate (ZnSOa-"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 20011Q of water was prepared and added dropwise to the above solution while stirring. Immediately, a white precipitate was formed. This precipitate was filtered, washed with water, and dried. The obtained white powder was recrystallized from a mixed solvent of water and ethanol. 24.2 g of crystals were obtained.

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

cAA3 B-(N-cyclohexyl-N-methylamino-6-methyl-7-anilite fluorane 20 parts 10% aqueous solution of hydroxyethyl cellulose 20 parts water
6 parts [Liquid B] Antipyrine complex of zinc thiocyanate 20 parts 5% aqueous solution of methylcellulose 20 parts water
60 parts [Liquid C] Tetramethylene glycol diphenyl ether (compound of Compound Example No. 4, melting point 99-100°C) 20 parts 5% aqueous solution of methylcellulose 20 parts water

60 parts [Liquid D] Urea-formalin resin fine powder 20 parts 5% methylcellulose aqueous solution 20 parts water
Next, 10 parts of liquid A, 30 parts of liquid 8, 30 parts of liquid C, 20 parts of liquid D, and 10 parts of a 20% alkaline aqueous solution of isobutylene-maleic anhydride copolymer were mixed to prepare a thermosensitive coloring layer forming liquid. This is coated on high-quality paper with a basis weight of 50 g/rd to a dry adhesion of 4 to 4.
After coating and drying at a rate of 5 g/nr to form a heat-sensitive coloring layer, the surface of the layer was further calendered to give a surface smoothness of 500 to 600 seconds to prepare a heat-sensitive recording material (a).

Example 2 Thermal recording material (b) 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.
It was created.

(E) Liquid ethylene glycol diphenyl ether (compound of Compound Example No. 2, melting point 97-98°C) 20 parts 10% aqueous solution of methylcellulose 20 parts Comparative Example 1 Real M! A heat-sensitive recording material (c) was prepared in the same manner as in Example I except that water was used instead of the CC'J solution in Example I.

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

[Do] Liquid stearamide 20 parts 5% aqueous solution of methylcellulose 20 parts water
60 copies or more of the heat-sensitive recording materials (a) to (d) obtained as described above were printed using a thermal printing experimental device having a thin-film head manufactured by Matsushita Electronics MS, at a head power of 0.45 seconds/dot and a line recording time of 2
0m5ec/Q-scan line density 8x3.85 dots/m
- pulse width is 1.6.2.0.2.4 (mse
c) and measure the print density using Macbeth Densitometer RD-5.
14 (filter W-106). The results are shown in Table-1.

Table 1 Next, thermal recording materials (a) to (d) were printed using a thermal gradient tester (Toyo Seiki Layer) 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.
/cJ for 24 hours, the sample 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, cottonseed oil was applied thinly to the background and colored areas of the similarly printed samples and stored at room temperature for 24 hours. No discoloration was observed.

Next, place a sample printed in the same way on the itc
1oon+ cut out into square meters and fill with 80mm of tap water
The sample was immersed in a Q beaker at room temperature for 24 hours, taken out and dried, and the change in density of one 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 that utilizes a color-forming reaction between a leuco dye and its color developer, the color developer may be of the following formula (
In addition to using an antipyrine complex of zinc thiocyanate represented by I), as an auxiliary component, the following general formula (II) is used.
A heat-sensitive recording material characterized by using a diether compound represented by: Formula (I): ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) General formula (II): ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (In the formula, R is alkylene with 1 to 10 carbon atoms. group or cycloalkylene group, X and Y represent hydrogen, lower alkyl group, alkoxy group, aryloxy group, aralkyloxy group, acyl group, acyloxy group or halogen atom,
(X and Y may be the same or different)