JPH0425491A - Heat-sensitive recording body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a heat-sensitive recording medium, and in particular to a heat-sensitive recording medium that has high whiteness and excellent suitability for high-speed recording.

[Conventional technology]

Thermosensitive recording materials that utilize a heated coloring reaction between normally colorless or light-colored leuco dyes and phenols or organic acids have been published in Japanese Patent Publications No. 43-4160, No. 14039-1983, No. 27736-1973, etc. , has been widely put into practical use. In recent years, such heat-sensitive recording materials have been widely used as various information recording materials due to their advantages such as the ability to form colored images simply by heating and the ability to make recording devices relatively compact. . In particular, the devices of thermal facsimiles, thermal printers, etc. that use such thermal recording materials have been improved, and it has become possible to perform high-speed printing and high-speed image formation, which was previously difficult. device,
As the speed of hardware increases, the heat-sensitive recording media used are required to have significantly higher recording sensitivity than before. A number of proposals have been made to meet this need, many of which involve the combination of leuco dyes and color formers in combination with thermofusible substances.

These thermofusible substances are called sensitizers, such as 1-hydroxy-2-naphthoic acid phenyl ester (Japanese Patent Application Laid-open No.
No. 191089), p-hensyl biphenyl (Japanese Patent Application Laid-open No. 6
0-82382), pencil naphthyl ether (JP-A-58-87094), dibenzyl terephthalate (
JP-A No. 5898285), Hensyl p-benzyloxybenzoate (JP-A No. 5'120169), diphenyl carbonate, ditolyl carbonate (JP-A No. 58-136489)
, m-terphenyl (JP-A-57-89994), 1
．． 2-bis(m-tolyloxy)ethane (Japanese Patent Application Laid-open No. 1983-
56588), 1.5bis(p-methoxyphenoxy)-3-oxapentane (JP-A No. 62-181183), benzyl oxalate, p-methylbenzyl oxalate, o-chlorobenzyl oxalate (JP-A No. 62-181183), Showa 64
-1583), etc.

[The problem that the invention attempts to solve]

When a heat-sensitive recording material containing such a thermofusible substance is heated,
First, the thermofusible substance is melted and the dye and coloring agent are dissolved therein, whereby the two are mixed at the molecular level and a coloring reaction is induced.

Therefore, these thermofusible substances must have an appropriate melting point (preferably 80 to 120 DEG C.) and have excellent compatibility with dyes and coloring agents. In addition, in order not to reduce the whiteness of the heat-sensitive recording material, it is desirable that these thermofusible substances are extremely poorly soluble in water and do not color the heat-sensitive coloring layer, and furthermore, they should not be sublimated. It is desirable to have characteristics such as low sex or low sex. The latter is thought to be particularly closely related to the so-called whitening phenomenon, in which the heated colored portion of a heat-sensitive recording material becomes powdery over time, and is an extremely important property for the practical use of heat-sensitive recording media. becomes. Furthermore, such heat-sensitive recording materials are often temporarily placed at relatively high temperatures of 60°C to 70°C during use, and it is desired that color development be suppressed to a low level at these temperatures (see below). , this is called heat resistance).

Another important feature is that it is relatively inexpensive when used industrially. Thermofusible substances are as described above.
Although many materials have been proposed in the past, there are very few materials that meet all of the above requirements, and there has therefore been a need for new materials that meet these requirements.

The present invention solves the problems of conventional sensitizers by providing a new thermofusible substance to be used together with the aforementioned leuco dye and coloring agent, thereby achieving high recording sensitivity and high-quality recorded images at high speed. The object of the present invention is to provide a heat-sensitive recording material that can be formed using the following methods.

[Means to solve the problem]

In order to achieve the above object, the present inventors developed a method of coloring a sheet-like substrate by reacting it with a colorless or light-colored dye precursor formed on at least one surface of the sheet-like substrate under heating. In a thermosensitive recording material having a thermosensitive coloring layer containing a coloring agent, the thermosensitive coloring layer has the following general formula [
I] Dicinnamyl ester of a dicarboxylic acid is used as a sensitizer, and n=1. 2. 3. We have examined in detail the case where it is included as 4. As a result, when n-4 in the above general formula, that is, cinnamyl adipate, is used, it has been proposed as a representative thermofusible substance (Japanese Patent Publication No. 14531/1983) and has been put into practical use. Compared to higher fatty acid amides such as stearic acid amide and palmitic acid amide, there is no reduction in whiteness.
Furthermore, the present inventors have discovered that extremely high recording sensitivity and heat resistance can be obtained without experiencing a phenomenon such as whitening that deteriorates the quality of colored images over time, leading to the achievement of the present invention. When compounds of n-1, n=2, and n=3 in the above general formula [1] are synthesized, their melting points are 58°C, 140°C, and 136°C, respectively, and the sensitization of heat-sensitive recording materials It must have a low melting point to be used as an agent.

The reason why the particular thermofusible substance mentioned above or the color development sensitivity of the heat-sensitive recording material containing it is improved is not sufficiently clear, or the compound has an appropriate melting point and the color developer It is presumed that this is because it has moderate compatibility with dye precursors.

In addition, the reason why the compound of the present invention does not reduce whiteness is due to its low solubility in water, and the reason why there are extremely few phenomena that deteriorate recorded image quality, such as whitening, is due to its low sublimation property.
It is thought that the reason why it has heat resistance is because it has an appropriate melting point.

The compounds of the present invention can be synthesized by various synthetic methods, and representative synthetic reactions are shown below.

However, in the above formula, n represents 4, X represents a halogen atom, and M represents an alkali metal ion.

The compound of the present invention is used together with a leuco dye and a coloring agent.

Further, it can be used in combination with other sensitizers within a range that does not impair the desired effects of the present invention. The amount of the compound of the present invention used is 10 to 1000% by weight, preferably 50 to 300% by weight, based on the color former.

The heat-sensitive coloring layer using the compound of the present invention mainly consists of leuco dyes,
It consists of a coloring agent made of phenols or organic acids, and the compound of the present invention. Further, the coloring layer preferably contains an inorganic pigment, and may further contain waxes if necessary. In addition, a binder for fixing these components to the support is included as an essential component.

The content of the leuco dye in the heat-sensitive coloring layer is generally 5 to 20% by weight, and the content of the color developer is generally 10 to 40% by weight.
It is. The binder content is generally 5 to 20% by weight, and when white pigments and waxes are included, the content is generally 10 to 50% by weight and 5 to 30% by weight, respectively.

As the leuco dye, conventionally known ones may be used, and examples include the following.

Crystal violet lactone, 3-(N-ethyl-N
-isopentylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6methyl-7- (
o,p-dimethylanilino)fluorane, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3-pyrrolisino6-methyl-7-anilinofluorane, 3-dibutylamino -6-Methyl-7-anilinofluorane, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7anilinofluorane, 3-
diethylamino-7(0-chloroanilino)fluoran, 3-diethylamino-7-(rn-trifluoromethylaninono)wallaoran 3-eneethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-6-methylfluoran, 3 -cyclohexylamino-6-chlorofluorane. Two or more of these may be used in combination.

As the coloring agent made of phenols or organic acids, any conventionally known coloring agent may be used, examples of which include those listed below.

Hisphenol A1p-Hydroquine Hensyl benzoate (
JP-A-52-140483), hisphenol S, 4
-Hi1Heloxy-4°-Isopropyloxin phenylsulfone (JP-A No. 6013852), 1.1-Hydroxy(4-hydroxyphenyl)cyclohexane, 1.7-
(Hydroxyphenylthio)-3,5-dioxahebutane (JP 59-52694).

Here, as the so-called sensitizer that can be used in combination with the compound of the present invention, a thermofusible organic compound with a melting point of 80 to 120°C is used, and these have been explained by giving typical examples. .

Further, organic or inorganic pigments used in the coloring layer include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay,
In addition to inorganic fine powders such as fired clay, talc, and surface-treated calcium carbonate and silica, urea-formalin resin,
Examples include organic fine powder such as styrene/methacrylic acid copolymer and polystyrene resin.

Furthermore, the coloring layer of the present invention may contain various waxes as required. They may be known ones such as paraffin, amide wax, bisimide wax, and metal salts of higher fatty acids. Also, regarding the adhesive,
Polyvinyl alcohol of various molecular weights, starch and its derivatives, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic amide/acrylic ester copolymer, acrylic amide/acrylic Acid ester/methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate,
In addition to water-soluble polymers such as gelatin and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymers,
Latexes such as polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/'butadiene/acrylic copolymer, etc. can be used.

A mixture that develops color when heated by appropriately mixing these materials is applied to paper, coated paper whose surface is coated with clay plastic, synthetic paper made mainly from plastic, or even plastic film, and then used to create a heat-sensitive recording material. Nasu. The coating amount is 1 to Log when the coating layer is dry.
/rrf is preferred, and 2 to 7 g/'rd is particularly preferred.

In this way, the heat-sensitive recording material obtained by the present invention has excellent high-speed recording suitability, high whiteness, and does not exhibit undesirable properties such as whitening in the recorded image area.

EXAMPLES The present invention will be specifically explained below with reference to Examples. Unless otherwise specified, numbers are in parts by weight.

〔Example〕

Synthesis Example 1 Synthesis side of the compound of the present invention 12.0 g of cinnamyl alcohol, 10 m
Add 1 part of dimethylaniline and 30 m of dry diethyl ether and stir well. To this, 7.2 g of adipic acid dichloride was slowly added dropwise from the dropping funnel. At this time, the temperature of the reaction solution rises, and the reflux of ether stops.

At the same time, a large amount of white solid is produced. Another 20m1
of ether and continue stirring #IWt for 4 hours.

The white solid produced is separated by filtration, washed with 10% sulfuric acid, followed by water, and dried. 11.6 g of white solid was obtained. The melting point after recrystallization from ethyl alcohol was 98°C. The synthesized product was confirmed to be cinnamyl adipate by measurements of nuclear magnetic resonance spectra and mass spectrometry spectra.

Formula [I] (n=1.2゜3) in the same manner as Synthesis Example 1
A compound represented by was obtained. However, instead of 7.2 g of adipic acid cyclolite in Synthesis Example 1 as the starting material,
5.6 g of malonic acid dichloride, 6.2 g of succinic acid dichloride, and 6.8 g of glutaric acid dichloride were used. Other treatments were performed in the same manner as in Synthesis Example 1 to obtain cinnamyl malonate (melting point 58°C), cinnamyl succinate (melting point 40°C), and cinnamyl glutamate (melting point 36°C). The structure of each compound was confirmed by nuclear magnetic resonance spectroscopy, and the quality was confirmed by measurement of analytical spectra.

Example 1 ■ Preparation of dispersion A 3-(N-Isopentyl-N-ethylamino)6-methyl-7-ayurifluorane 20 parts Polyvinyl alcohol 10% solution 10 parts Water
70 parts of this composition was ground to an average particle size of 1 μm using a sand grinder.

■ Adjustment of dispersion B 4.4゛ -Isopropylidenehyphenol 10 parts Cinnamyl adipate 10 parts Polyvinyl alcohol 10% solution 10 parts Water
70 parts of this composition was ground to an average particle size of 1 μm using a sand grinder.

■ Adjustment of coloring layer 40 parts of the above liquid A, 160 parts of liquid B, 4 parts of calcium carbonate pigment
0 parts, 20 parts of a 30% paraffin dispersion, and 180 parts of a 10% polyvinyl alcohol aqueous solution were mixed, stirred, and stopped for coating. This coating solution was applied to a base paper of 50 g/'rrf so that the coated amount after drying was 7°0 g/'d and dried to obtain a heat-sensitive recording paper.

Example 2 ■ Adjustment of pigment undercoated paper: 85 parts of fired lay (trade name: Ansilex) and 320 parts of water.
A coating liquid obtained by mixing 40 parts of a styrene-butadiene copolymer emulsion (solid content 50%) and 50 parts of a 10% oxidized starch aqueous solution in the dispersion obtained by dispersing in 48 gy
'rd base paper was coated to give a coated amount of 7.0 g/r+ (after drying) to obtain a pigment-primed paper.

■ Formation of coloring layer 50 parts of solution A, 200 parts of solution B, 25 parts of calcium carbonate, 3
20 parts of a 0% paraffin dispersion and 180 parts of a 10% aqueous polyvinyl alcohol solution were mixed and stirred to prepare a coating liquid. The obtained coating liquid was applied to the pigment undercoated paper so that the coating amount after drying was 5.
It was coated and dried at a concentration of 0 g/I to obtain heat-sensitive recording paper.

Comparative Example I In preparing the B solution, instead of cinnamyl adipate, 1
A thermosensitive recording paper was obtained in the same manner as in Example 2 except that -hydroxynaphthoic acid phenyl ester was used.

Comparative Example 2 In the preparation of liquid B, instead of cinnamyl adipate,
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that stearic acid amide was used.

The four types of thermal papers obtained as described above were treated with a supercalenter so that the surface smoothness was 600 to 1000 seconds as measured by a smoothness meter. The samples thus obtained were subjected to measurement of recording sensitivity, measurement of color density of uncolored areas on the recording layer surface, and comparative test of whitening, and the results are shown in Table 1.

Measurement of recording sensitivity and blank area densityRecording sensitivity was measured using a Toyo Seiki thermal gradient tester at a temperature of 120℃.
°C Pressure 2,5 kg/”Cnf]-00ms
The c sample was heated, and the color density at that time was measured at a Maches density of 51RD-91.4, which was taken as a value representative of the recording sensitivity of thermal paper. The density of an uncolored area (blank area) on the surface of the recording layer was measured using the same density material, and was taken as a representative value of whiteness.

Measurement of static color density and temperature 70°C pressure 2. The sample was heated for 5 seconds at 5 kgy"c2, and the color density at that time was measured at the above concentration. This is called static color development (70°C). When the sample is actually used as recording paper for facsimile communication, the ambient temperature is kept at 60 to 7
It is known that the temperature rises to 0°C, and the above value is
This is a measure of whether the non-printed area can maintain its level of whiteness even under such a high temperature environment, and it is desirable that the color density be 2 or less.

Evaluation of whitening For whitening, color the sample at a temperature of 150°C using the above test machine,
The printed area was left in an environment of 40°C and 190% for 24 hours, and changes in the surface were sensory evaluated.

In the table, ○ indicates that no change was observed in the colored printed area, and × indicates that the printed surface became powdery, so-called whitening.

Table 1 [Effects of the Invention] Since the present invention uses a new thermofusible material, it has excellent high-speed recording suitability, high whiteness, little static coloring, and undesirable problems such as whitening. The present invention provides a thermal recording material that does not induce any phenomena and has extremely well-balanced properties in terms of quality.

Claims (1)

[Scope of Claims] 1. A sheet-like substrate; a colorless or light-colored paint precursor formed on at least one surface of the sheet-like substrate;
1. A heat-sensitive recording material, comprising a heat-sensitive coloring layer containing a coloring agent that develops color by reacting with heating, the heat-sensitive coloring layer containing cinnamyl adipate represented by the following structural formula. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼