JPH03262683A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal color forming layer having extremely high recording sensitivity by providing the thermal color forming layer containing a colorless or light-colored dye precursor and a developer reacting with the dye precursor under heating to form a color and further adding a specific ether compound to the thermal color forming layer. CONSTITUTION:A thermal recording material has a sheet like base material and the thermal color forming layer formed at least to one surface of the base material and containing a colorless or light-colored dye precursor and a developer reacting with the dye precursor under heating to form a color and the thermal color forming layer further contains at least one kind of an ether compound represented by general formula (wherein Ar is a - - group or - - - group and R is a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom). Since this thermal recording material has the thermal color forming layer containing a sensitizer composed of a novel heat-meltable material, it is excellent in high speed recording properties, has high whiteness, generates no undesirable phenomenon such as whitening and has properties extremely well-balanced in the aspect of quality and extremely high practical value.

Description

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

[Conventional technology]

Heat-sensitive recording materials that utilize a color-forming reaction under heating between normally colorless or light-colored leuco dyes and phenols or organic acids are disclosed in, for example, Japanese Patent Publication No. 43-4160 and Japanese Patent Publication No. 45-14039.
It is disclosed in Japanese Patent Publication No. 48-27736, etc., and has been widely put into practical use. In recent years, such heat-sensitive recording materials have been known to form colored images simply by heating;
Due to its advantages such as the fact that the recording device can be made relatively compact, it is widely used as a variety of information recording materials. 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 considered difficult. As the speed of such equipment and hardware increases, the heat-sensitive recording media used are required to have significantly improved recording sensitivity than before. Many proposals have been made to meet this requirement, but
Many of these proposals involve combinations of dye precursors and color developers.
or is further characterized by the combined use of a thermofusible substance. The above-mentioned thermofusible substance is also called a sensitizer, and examples include 1-hydroxy-2-naphthoic acid phenyl ester (Japanese Patent Application Laid-open No. 191089/1989), p-benzylbiphenyl (Japanese Patent Application Laid-open No. 82382/1982), Benzyl naphthyl ether (JP-A-58-87094),
Dibenzyl terephthalate (JP-A No. 58-98285), benzyl p-benzyloxybenzoate (JP-A No. 57-98)
-201691), diphenyl carbonate, di) IJ
(Japanese Patent Publication No. 58-136489), m-terphenyl (Japanese Patent Application Publication No. 57-89994), 1,2-bis(m-tolyloxy)ethane (Japanese Patent Application Publication No. 60-56588), etc. There is.

[Problem to be solved by the invention]

When a heat-sensitive recording medium containing a thermofusible substance as described above is heated, the thermofusible substance first melts, which dissolves the dye precursor and the color developer, so that both are dissolved at the molecular level. They mix together and a color reaction is induced. Therefore, these thermofusible substances have a suitable melting point (preferably 60-140
°C) and must have excellent compatibility with the dye precursor and color developer. It is also important not to reduce the whiteness of the heat-sensitive recording medium, and for this purpose, it is desirable that the thermofusible substance has extremely low solubility in water, and also has properties such as low sublimation. It is desirable to be present. The sublimability of thermofusible substances is
In particular, it is thought to be closely related to the so-called whitening phenomenon in which the heat-colored portion of a heat-sensitive recording material becomes powdery over time, and is an extremely important property for the practical use of a heat-sensitive recording material. As mentioned above, many thermofusible materials have been proposed in the past, but there are few that satisfy all of the above conditions, and therefore there has been a demand for new materials.

The present invention has a heat-sensitive coloring layer formed using a novel thermofusible substance together with the dye precursor and color developer described above, and has significantly improved recording sensitivity without deteriorating recording performance. The purpose is to provide a thermosensitive recording medium.

[Means and actions to solve the problem]

The heat-sensitive recording material of the present invention includes a sheet-like substrate, a colorless or light-colored dye precursor formed on at least one surface of the sheet-like substrate, and a dye precursor that reacts with the dye precursor under heating to develop color. and a thermosensitive coloring layer containing a color developer, the thermosensitive coloring layer having the following general formula (I): (1) 10 (represents a group, R is a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom).

The present inventors discovered that the use of the thermofusible substance of the above formula (I) as a sensitizer has been proposed as a typical thermofusible substance (Japanese Patent Publication No. 14531/1983), and Compared to the use of higher fatty acid amides such as stearic acid amide and palmitic acid amide, which are in practical use, there is no reduction in whiteness, and the phenomenon of whitening that deteriorates the quality of colored images over time. The inventors have discovered that a heat-sensitive coloring layer having extremely high recording sensitivity can be obtained without experiencing the above problems, and have completed the present invention.

The present invention is directed to a thermosensitive recording material that utilizes a color reaction between a colorless or monochromatic basic leuco dye (dye precursor) and a color developer that can develop a color by contacting the dye precursor. It is characterized in that the heat-sensitive coloring layer contains the compound of formula (I) above. The reason why a specific thermofusible substance (hereinafter referred to as a sensitizer) as mentioned above improves the coloring sensitivity of a thermosensitive coloring layer is not fully clear, but the reason is that this compound has a low viscosity in the molten state and is a dye precursor. It is assumed that part of the reason for this is that it has appropriate compatibility with the body and color developer. Furthermore, the reason why the compound of formula (1) above does not reduce the whiteness of the thermosensitive coloring layer is because it is poorly soluble in water, and furthermore, the compound of formula (1) deteriorates the recorded image quality such as whitening. It is thought that the reason why this is extremely rare is due to its low sublimability. However, the inventor does not adhere to this interpretation. Specific examples of the sensitizer of formula (1) used in the present invention include the following: 60'! ″
is 7I· space below CRs These compounds can be synthesized by various known synthetic methods, but most conveniently, they can be synthesized easily and in high yield using the -iliamson reaction below. In the reaction formula below, Ar and R are the same as defined above.

(1) The sensitizer of formula (1) is contained in the thermosensitive color forming layer together with the dye precursor and the color developer. Further, other sensitizers may be used in combination with the sensitizer within a range that does not inhibit the desired effects of the present invention. The amount of the sensitizer used in the present invention is based on the weight of the developer,
It is preferably 10 to 1000% by weight, and 50 to 3% by weight.
00% by weight is more preferable.

The thermosensitive coloring layer containing the sensitizer of the present invention mainly contains dye precursors,
It contains a color developer made of phenols or organic acids, and a binder for binding these and bonding the thermosensitive coloring layer to the sheet-like substrate, but preferably further contains an inorganic pigment, and further contains an inorganic pigment. If necessary, waxes may be included.

The leuco dye used as the dye precursor can be selected from conventionally known leuco dyes. For example, the dyes include crystal violet lactone, 3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-
Anilinofluorane, 3-diethylamino-6-methyl-7=(o + p-dimethylanilino)fluoran,
3-(N-ethyl-P-toluidino)-6-methyl-7
-anilinofluorane, 3-pyrrolidino-6methyl-7
-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-(N-cyclohexine-N-methylamino)-6-methyl-7-anilinofluorane, 3-diethylamino -7-(0-chloroanilino)fluoran, 3-diethylamino-7-(m-)
1 selected from trifluoromethylanilino)fluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6-methylfluorane, and 3-cyclohexylamino-6-chlorofluorane, etc. More than one species can be used.

As the color developer made of phenols or organic acids, conventionally known ones can be used. For example, as a color developer, bisphenol A, benzyl p-hydroxybenzoate (Japanese Patent Publication No. 140483/1983), bisphenol S, 4-hydroxy-4'-isopropyloxydiphenyl sulfone (Japanese Patent Application Publication No. 6013852), 1, 1-di(4-hydroxyphenyl)cyclohexane, 1.7-
One or more selected from di(4-hydroxyphenylthio)-3,5-dioxahebutane (JP-A-59-52694) and the like can be used.

Here, as other sensitizers that can be used in combination with the sensitizer of the present invention, thermofusible organic compounds with a melting point of 50-150°C are used, and representative examples of these have already been given. As explained.

In addition, examples of organic or inorganic pigments that can be used in the heat-sensitive coloring layer include calcium carbonate, silica, zinc oxide,
In addition to inorganic fine powders such as titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, calcined rhetarch, and surface-treated calcium carbonate and silica, as well as urea-formalin resin, styrene/methacrylic acid, etc. Examples include polymers and organic fine powders such as polystyrene resins.

Furthermore, the heat-sensitive coloring layer of the present invention may contain various waxes as required. As for those waxes,
Known waxes such as paraffin, amide wax, bisimide wax, and metal salts of higher fatty acids can be used. In addition, the adhesives include polyvinyl alcohol of various molecular weights, starch and its derivatives, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic acid amide/acrylic acid ester, etc. Water-soluble polymeric materials such as polymers, acrylic acid amide/acrylic ester/methacrylic acid ternary copolymers, styrene/maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, and casein, and Polyvinyl acetate, polyurethane, styrene/butadiene copolymer,
Latexes such as polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer, and styrene/butadiene/acrylic copolymer can be used. .

The sheet-like substrate used in the thermal recording medium of the present invention is paper,
Coated paper whose surface is coated with clay plastic, etc.
You can choose from synthetic paper, which is mainly made from plastic, or plastic film. A coating liquid containing a mixture of the above-mentioned necessary components is applied onto at least one surface of such a sheet-like substrate and dried to produce a heat-sensitive recording material.

The coating amount is preferably 1 to 15 g/n, particularly preferably 2 to 10 g/n, when the coating liquid layer is dry.The heat-sensitive recording material of the present invention thus obtained is suitable for high-speed recording. It has excellent whiteness and does not cause undesirable phenomena such as whitening in recorded image areas.

〔Example〕

The present invention will be specifically explained below with reference to Examples.

Incidentally, unless otherwise specified, "1 part" and "%" refer to "part by weight" and "% by weight," respectively.

18.6 g of 4,4'-dihydroxydiphenyl and 3
6.0 g of phenethyl bromide and 12.3 g of potassium hydroxide were added to 200 cc of acetone under a nitrogen gas stream, and the bath temperature was heated to 85° C. to reflux the acetone. After continuing to reflux for a day and night, acetone was distilled off.

Ether was added to this residue to perform ether extraction, and the resulting ether extract was washed with an alkali and acid, and then the ether was distilled off to obtain a light brown solid. This was recrystallized from ethyl alcohol to obtain 10.5 g of white solid. Its melting point was 104-106°C.

This solid product was confirmed to be 4,4'-bis(2-phenylethoxy)diphenyl by mass spectrometry and nuclear magnetic resonance spectroscopy.

17.6 g of hydroquinone, 59.2 g of phenethyl bromide, and 18.0 g of potassium hydroxide were added to 200 cc of acetone under a nitrogen gas stream, and the acetone was heated to 85°C. was refluxed. After continuing to reflux for a day and night, acetone was distilled off. Ether was added to this residue to perform ether extraction, and the resulting ether extract was washed with an alkali and acid, and then the ether was distilled off to obtain a pale brown solid. This was recrystallized from ethyl alcohol to obtain 15.1 g of white solid.

Its melting point was 66-67°C. Mass spectrometry and nuclear magnetic resonance spectrometry revealed that this solid product was
．． It was confirmed that it was 4'-bis(2-phenylethoxy)benzene.

S] 11th A thermosensitive recording paper was prepared by the following procedure.

polyvinyl alcohol 10% liquid 0 water 0 The above composition was subjected to a sand grinder, and the average It was ground to a particle size of 1μ.

polyvinyl alcohol 10% liquid 0 water 0 The above composition was subjected to a sand grinder, and the average The powder was ground until the particle size became one dimensional.

Meng-1 Wataru I ■■ Star 40 parts of liquid A above, 160 parts of liquid B, calcium carbonate pigment 4
0 parts, 20 parts of a 30% paraffin dispersion, and 180 parts of a 10% polyvinyl alcohol aqueous solution were mixed and stirred to prepare a coating liquid. This coating solution was coated on one side of base paper with a basis weight of 50 g/n so that the coated amount after drying was 7.0 g/n, and dried to form a heat-sensitive coloring layer, thereby producing heat-sensitive recording paper. .

The heat-sensitive recording paper obtained as described above was treated with a supercalender, and the surface smoothness was adjusted to 600-100.
It was set to 0 seconds. The samples thus obtained were subjected to the following tests to measure the recording sensitivity, measure the color density of the uncolored area on the recording layer surface, and compare whitening, and the results are shown in Table 1.

(a) Y hammer! The sample was heated for 100 milliseconds at a temperature of 120°C and a pressure of 2.5 kg/CI# using a Hado Toyo Seiki Equipment Inclination Tester, and the color density at that time was measured using a Macbeth Densitometer RD-914.
It was measured with This measured value represents the recording sensitivity of the thermal paper. The density of the uncolored area (blank area) on the surface of the recording layer was measured using the above densitometer, and the measured value was expressed as the degree of whiteness.

(b) 1. After coloring the sample at a temperature of 150°C using the above testing machine,
The printed area was left in an environment of 40°C and 590% for 24 hours, and changes in the surface were sensory evaluated. In Table 1, “
"Good" indicates that no change in the colored printed area is observed.
"Defect" indicates that so-called whitening, in which the printed surface becomes powdery, has occurred.

The test results are shown in Table 1.

Pig 1 Tei I A thermosensitive recording paper was prepared by the following procedure.

・ No.i 85 parts of fired lei (trade name: Ancilex) and 32 parts of water.
40 parts of styrene-butadiene copolymer emulsion (solid content 50%) and 10 parts of styrene-butadiene copolymer emulsion (solid content 50%)
% oxidized starch aqueous solution, and the resulting coating solution was applied onto one side of base paper with a basis weight of 48 g/rrf so that the coating amount after drying was 1.0 g/rt (pigment I created the undercoat paper.

50 parts of dispersion A, 200 parts of dispersion B, 2 parts of calcium carbonate
5 parts of a 30% paraffin dispersion, and 180 parts of a 10% polyvinyl alcohol aqueous solution were mixed and stirred to prepare a coating liquid. The obtained coating liquid was applied and dried on the pigment-coated surface of the pigment undercoated paper so that the coating amount after drying was 5.0 g/nf to form a thermosensitive coloring layer, thereby producing thermosensitive recording paper. .

The same test as in Example 1 was conducted using this thermosensitive recording paper.

The results are shown in Table 1.

Backyard ■The same operation as in Example 2 was performed. However, in preparing the B solution used for forming the thermosensitive coloring layer, 4.4'-bis(2-
phenylethoxy) diphenyl instead of 4,4'-
Bis(2-phenylethoxy)benzene was used.

The test results are shown in Table 1.

The same operation as in Example 1 was performed on this soup. However, in preparing Solution B, stearic acid amide was used instead of 4,4'-bis(2-phenylethoxy)diphenyl.

The test results are shown in Table 1.

For comparison, the same operations as in Example 2 were performed. However, in preparing Solution B, stearic acid amide was used instead of 4,4'-bis(2-phenylethoxy)diphenyl.

The test results are shown in Table 1.

Northern Comparison ■ The same operations as in Main Example 2 were performed. However, in the product manufactured by BitPi, 1-hydroxy-2-naphthoic acid phenyl ester was used instead of 4,4'-bis(2-phenylethoxy)diphenyl.

The test results are shown in Table 1.

Table 1 [Effects of the Invention] The heat-sensitive recording material of the present invention has a heat-sensitive coloring layer containing a sensitizer made of a new thermofusible material, so it has excellent high-speed recording suitability and high whiteness. Moreover, it does not induce undesirable phenomena such as whitening, has extremely well-balanced properties in terms of quality, and has extremely high practical value.

Claims (1)

[Claims] 1. A sheet-like substrate, and at least one of the sheet-like substrates.
A thermosensitive coloring layer formed on the surface and containing a colorless to light-colored dye precursor and a color developer that reacts with the dye precursor under heating to develop color, the thermosensitive coloring layer comprising: The following general formula (I): ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ・・・・・・(I) (However, Ar in the formula is ▲There are mathematical formulas, chemical formulas, tables, etc.)▼ group or ▲Mathematical formula, chemical formula , tables, etc. ▼ represents a group, and R represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom. body.