JPH0361075A - Thermal recording medium - Google Patents

Abstract

PURPOSE:To ensure that a high-quality recorded image ia formed at high speed using a highly sensitive thermal recording medium by adding a specific aromatic ether compound to a thermal coloring layer. CONSTITUTION:The subject medium consists of a sheet-like support and a thermal coloring layer which is formed on one surface of said support and contains a colorless or pale dye precursor and a colordeveloper causing the former to form a color through thermal reaction with the former. The thermal coloring layer contains at least one kind of aromatic ether compound shown by formula I. In formula I, R<1> to R<9> are independently a hydrogen atom or methyl group, and at least two of R<1> to R<5> are a methyl group. Furthermore, either two of R<2>, R<3> and R<4> represent methyl group.

Description

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

[Conventional technology]

Thermal recording materials that form colored images by utilizing a heated coloring reaction between normally colorless or light-colored leuco dyes and phenols or organic acids are disclosed in, for example, Japanese Patent Publication No. 434160, Japanese Patent Publication No. 45-14039, and Japanese Patent Publication No. 4827736. It is disclosed in the issue. In recent years, such heat-sensitive recording media,
It is widely used as a variety of information recording materials due to its advantages such as being able to form a colored image simply by heating and making the recording device relatively compact. In particular, improvements have been made to the devices of thermal facsimiles and thermal printers that use such thermal recording materials, and it has become possible to print at high speeds and form images at high speeds, which were previously considered difficult(2). It's coming. As the speed of such equipment and hardware increases, the thermal recording media used therein are required to have significantly higher recording sensitivity than before.

Many proposals have been made to meet these requirements, most of which involve combinations of dye precursors and color developers, and the combined use of thermofusible substances. These thermofusible substances are called sensitizers, such as 1-
Hydroxy-2-def-1-technic acid phenyl ester (JP-A-57-191089), p-hensyl biphenyl (
JP-A-60-82382), hensyl naphthyl ether (JP-A-58-87094), dihenzyl terephthalate (JP-A-58-98285), hensyl p-hensyloxybenzoate (JP-A-57201691)
, diphenyl carbonate, dil-IJ carbonate (JP-A-58-1
36489), m-terphenyl (JP-A-57-89)
994), and 1,2-bis(m-tolyloxy)ethane (Japanese Patent Application Laid-Open No. 60-56588).

(3) Problem to be solved by Invention C] When a heat-sensitive recording material containing a thermofusible substance as described above is heated, first, this thermofusible substance melts, and it becomes a dye,
By dissolving the color developer and the color developer, the two are mixed at the molecular level and a color reaction is induced. Therefore, these thermofusible substances have a suitable melting point (preferably 80-1
10°C), and it is also important to have excellent compatibility with dyes and color developers. In addition, in order not to reduce the whiteness of the heat-sensitive coloring layer, it is desirable that these heat-fusible substances have extremely low solubility in water, and they should also have properties such as low sublimability. desirable.

The latter characteristic 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 extremely important for the practical use of heat-sensitive recording media. It becomes a characteristic. In addition, when used, thermal recording materials in practical use are often exposed to relatively high temperatures of 60"C to 70°C, and even at such high temperatures, (4) color development occurs. It is desired that the heat resistance can be suppressed to a low level (this is called heat resistance).As mentioned above, many thermofusible materials have been proposed for heat-sensitive recording materials, but none that meet all of the above conditions. Therefore, there has been a need for new materials that can satisfy all of the above conditions.

The present invention includes a novel thermofusible material for use with the dye precursor and developer described above, thereby solving the problems of conventional sensitizers and producing high recording sensitivity and high quality recorded images. The object of the present invention is to provide a heat-sensitive recording material that can be formed at high speed.

[Means to solve problems]

The heat-sensitive recording material of the present invention includes a sheet-like support, a colorless to light-colored dye precursor formed on at least one surface of the sheet-like support, and a dye precursor formed on at least one surface of the sheet-like support, and a dye precursor formed by reacting with the dye precursor under heating. In a heat-sensitive recording material having a heat-sensitive color-forming layer containing a color developer that develops the color, the heat-sensitive color-forming layer further has the following general formula (I):r (wherein R1 and R9 are each independent from the other). represents a hydrogen atom or a methyl group, at least two of R1 to R5 represent a methyl group, and any two of R2, R3 and R4 represent a methyl group. It is characterized by containing one kind of

The above compound of general formula (1) is used as a thermofusible substance, that is, a sensitizer, and is known as a typical conventional thermofusible substance (Japanese Patent Publication No. 14531/1983), In addition, it does not cause a decrease in whiteness compared to stearic acid amide and higher fatty acid adducts such as balmitic acid adduct, which have been put into practical use. It is possible to form a heat-sensitive recording medium with extremely high recording sensitivity (6) without causing such a phenomenon.

The reason why the specific heat-melting compound (hereinafter referred to as sensitizer) as mentioned above improves the coloring sensitivity of the heat-sensitive recording layer is not sufficiently clear. It is presumed that part of the reason for this is that it has a low compatibility with dyes and color developers. Furthermore, the reason why this compound does not reduce the whiteness of the obtained recording medium is because it is intolerant to water, and the reason why phenomena such as whitening that deteriorate the recorded image quality are extremely rare is that This is thought to be due to its low sublimability. However, the inventor does not adhere to this interpretation. The following compounds can be cited as practical examples of the sensitizer compounds constituting the present invention.

■, 4-bis(3',4'-dimethylphenyloxy)henzen, 1,4-bis(3',5'-dimethylphenyloxy)
Hensen.

These compounds can be synthesized by various synthetic methods, but most conveniently, they can be synthesized easily and in high yields by the so-called Ulmann reaction (7) shown below. Here, R1 and R9 in the formula are defined as described above. Moreover, X represents a halogen atom.

A thermofusible substance containing the compound of formula (1) is included in the thermosensitive coloring layer together with a dye precursor and a color developer. Further, the compound 2N) can be used in combination with other sensitizers as long as the desired effects of the present invention are not inhibited. The content of the thermofusible substance of formula (1) in the thermosensitive coloring layer is preferably 10 to 1000% by weight based on the weight of the color developer, and 50 to 300% by weight. is more preferable.

The thermosensitive coloring layer of the present invention containing the compound of formula (1) includes a dye precursor, a color developer made of phenols, or an organic acid, and a color developer that binds these to each other. Contains (8) a binder (organic or non-organic) for adhesion to f! 1 pigment, and may further contain waxes if necessary.

Generally, the amounts of each bone contained in the thermosensitive coloring layer are 5 to 20% by weight of dye precursor, 10 to 40% by weight of color developer, 5 to 20% by weight of binder, 10 to 50% by weight of pigment, and 5% by weight of wax.
~30% by weight, and the sensitizer consisting of a thermofusible substance is 5% by weight.
It is preferably 40% by weight.

The dye precursor can be selected from conventionally known electron-donating colorless dyes, such as crystal hiolet lacone, 3-(N-ethyl-N-isopentyl-trichloride)).
-6-Medi-7-anilinofluorane, 3-diethylamino6-methyl7-anilinofluorane, 3-diethylamino6-methyl-7-(o,p-dimethylanilino)fluorane, 3-(N -ethyl-p-1-binder) 6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-sibdelamino-6-methyl-7-anilinofluorane, 3-
(N-cyclohexyl-N-me(9) thylamino)-6-methyl-7-anilinofluorane,
3-diethylamino-7-(0-chloroanilino)fluoran, 3-diethylamino-7(m-trifluoromethylanilino)fluoran, 3-diethylamino-6-
Methyl-7-chlorofluorane, 3-diethylagono-6-methylfluorane, and 3-cyclohexylamino-6-chlorofluorane may be used; these dye precursors may be used alone or It is also possible to use a mixture of two or more types.

As the color developer made of phenols or organic acids, conventionally known electron-accepting acidic substances such as benzyl bisphenol A1p-hydroxybenzoate (JP-A-5
2-140483), bisphenol S, 4-hydroxy-4'-isopropyloxydiphenyl sulfone (
1,1-di(4-hydroxyphenyl)cyclohexane, and 1,7-di(hydroxyphenylthio)-3,5-dioxahebutane (JP-A-60-13852)
You can choose from JP-A-5952694), etc.

(10) Other thermofusible organic compounds can be used as so-called sensitizers that can be used in combination with the compound of formula (1), but representative examples of these have already been given and explained! J.I.
That's exactly what I did.

Inorganic pigments used in the heat-sensitive coloring layer include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide J1, zinc hydroxide, barium sulfate, clay, calcined clay, talc, and surface-treated pigments. There are inorganic fine powders such as calcium carbonate and carbonate, and organic pigments include urea-formalin resin, styrene/methacrylic acid copolymer,
and fine powder of organic resin such as polystyrene resin.

Furthermore, the heat-sensitive coloring layer of the present invention may contain various one laths as required. They can be selected from known ones such as paraffin, Ami-F wax, bisigode wax, and metal salts of higher fatty acids. Furthermore, as a binder, polyvinyl alcohol of various molecular weights,
Starch and its derivatives, methoxycellulose, carboxyme(11), cellulose derivatives such as methylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide/acrylic acid ester copolymer, acrylamide/ Acrylic ester/
7. Water-soluble polymers such as methacrylic acid terpolymer, styrene/maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein.
Polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, polybutylmethacrylate-1, ethyl/vinyl acetate Latexes of water-insoluble polymeric materials such as copolymers and styrene/butadiene/acrylic copolymers can be used.

To produce the heat-sensitive recording material of the present invention, a coating solution containing each of the above components is applied to paper, Corteno F paper whose surface is coated with clay or plastic, synthetic paper made mainly from plastic, or plastic paper. The heat-sensitive recording layer may be formed by coating on at least one side of a sheet-like support made of a thin film and drying. The coating amount of the coating liquid is 1 when the coating liquid layer is dry.
It is preferable that the heat-sensitive coloring layer is formed in an amount of ~10 g/r4, and it is more preferable that the dry heat-sensitive coloring layer is formed in an amount of 2 to 7 g/r4. The heat-sensitive recording medium of the present invention has excellent high-speed recording suitability,
It also has a high degree of whiteness and does not exhibit undesirable properties such as whitening in recorded image areas, making it of high practical value.

〔Example〕

The present invention will be specifically explained below using Examples.

Note that unless otherwise specified, "parts" and "%" refer to "parts by weight" and "% by weight."

37.0. A heated melt of 3,4-dimethylphenol was reacted with 17.0 g of potassium hydroxide to prepare potassium salt of dimethylphenol. 50 ml of toluene was added to this molten mixture and heated, and further, toluene was distilled off from this mixture, and at the same time, water generated in the system (13) was removed by the principle of azeotropic distillation. To the thus obtained white solid was added 50 ml of pyridine, further added 23.6 g of 1,4-diromohenzene, and further added a small amount of cupric chloride, and the resulting reaction mixture was heated and heated. After reacting for 16 hours, the resulting reaction mixture was cooled, the reaction product was extracted with ether, and ether and pyridine were distilled off from the extract to obtain a brown solid (crude product).

This was recrystallized from ethyl alcohol to obtain 22.3 g of a white solid. Its melting point was 106"C. Mass spectrometry and nuclear magnetic resonance spectroscopy confirmed that this solid was 1,4-bis(3",4'-dimethylphenyloxy)henzene.

The same operation as in Synthesis Example 1 was performed. However, 3,5-dimethylphenol was used instead of 3,4-dimethylphenol. 23.0 g of white solid was obtained. Its melting point is 1
It was 03°C. Further, by mass spectrometry and nuclear magnetic resonance spectroscopy, it was determined that this solid (14) was 1,4-bis(3',5'-dimethylphenyloxy)benzene.

Implementation-drying L-shi Thermosensitive recording paper was produced by operating the F rudder.

Q - Public fungus 4 sinking □ Aiming for a pedigree --- Magic one ---------------- Power ---------- Minutes ---
- Part - Polyvinyl alcohol water, 7.

This composition was subjected to a sand grinder, and the component particles were crushed to an average particle diameter of 1 μm.

(15) Water
70 This composition was subjected to a sand grinder, and the component grains were crushed to an average particle size of 1 ryo.

0 ---- Sensation - Heat J 11 nights] Written by Akihito 40 parts above, 160 parts of liquid B, 40 parts of calcium carbonate pigment, 20 parts of 30% paraffin dispersion, and 10%
Mix and stir 180 parts of polyvinyl alcohol aqueous solution,
It was used as a coating liquid. This coating liquid was applied and dried on one side of a base paper having a basis weight of 50 g/rrr so that the weight after drying was 7.0 g/ni to prepare a thermosensitive recording paper.

, with varnish. h Ema Mito 2 Lee - 5 Koichi A thermosensitive recording paper was produced by the following procedure.

Q - 141 parts of salmon - Preparation - 85 parts of fired clay (trade name: Ansilex) and 320 parts of water
40 parts of styrene-butadiene copolymer emulsion (solid content 50%) and 1
Mix 50 parts of 0% oxidized starch aqueous solution, apply the resulting coating liquid onto one side of base paper with a basis weight of 48 g/m so that the weight after drying becomes 7.0 g/rrr, and dry to coat the pigment. I got the base paper.

(16) Beans) 50 parts of J-sankyo-kabutagemu-sha human bone dispersion, 200 parts of B-dispersion, 2 parts of calcium carbonate
5 parts, 20 parts of 30% paraffin dispersion, and 80 parts of 10% borihinyl alcohol water solution] were mixed and stirred,
It was used as a coating liquid. The obtained coating liquid was applied to the pigment layer of the pigment undercoated paper so that the weight after drying was 5.0 g/nl and dried to obtain a heat-sensitive recording paper.

The same operations as in Example 2 were carried out. However, when preparing liquid B, 1
, 1,4-his(phenoxy) instead of 4-bis(3'4'-dimethylphenyloxy)benzene
-2,5-dimethylhensen was used.

The test results are shown in Table 1.

The same operation as in Example 1 was carried out on a comparative plate. However, in preparing Solution B, stearic acid 5d was used instead of 1,4-bis(3'4'-dimethylphenyloxy)benzene.

The test results are shown in Table 1.

(17) Recording Example-i The same operation as in Example 2 was performed. However, in the preparation of Solution B, acetostearate was used instead of 1,4-bis(3',4'-dimethylphenyloxy)benzene.

The test results are shown in Table 1.

Hinaike I The same operation as in Example 1 was performed. However, in preparing liquid B, 14-bis(3',4'-dimethylphenyloxy)
1-hydroxy-2-naphthoic acid phenyl ester was used instead of benzene.

The test results are shown in Table 1.

The same operation as in Example 2 was carried out on a comparative plate. However, in preparing Solution B, 1,4-bis(2',4'-
Dimethylphenyloxy)benzene (melting point 62°C) was used.

The test results are shown in Table 1.

(18) M2□1 Tomoe;;□1];Su□□[)1 The same operation as in Example 2 was performed. However, in preparing Solution B, 1,4-bis(2',6'-dimethylphenyloxy)benzene (melting point 169°C) was used instead of 1,4-bis(3',4'-dimethylphenyloxy)benzene. was used.

The test results are shown in Table 1.

Comparative staining The same operation as in Example 2 was performed. However, in preparing Solution B, 1,4-bis(2',4',6-bis(2',4',6-
'-1-dimethylphenyloxy)benzene (melting point 17
0°C) was used.

The test results are shown in Table 1.

Comparative plate work The same operation as in Example 2 was performed. However, B? v. In the preparation, instead of 1,4-bis(3',4'-dimethylphenyloxy)benzene, 1,4-bis(2',3'
, 6'-)dimethylphenyloxy) Hensen (melting point 150°C) was used.

(19) The test results are shown in Table 1.

The same operation as in Example 2 was carried out. However, in preparing Solution B, instead of 1,4-bis(3',4'-dimethylphenyloxy)benzene,
dimethylphenyloxy)2,5-dimethylbenzene(
(melting point 131°C) was used.

The test results are shown in Table 1.

The same operation as in Example 2 was carried out. However, in preparing Solution B, 1.4bis(3',4'-dimethylphenyloxy)2.5-'''dimethyl was used instead of 1,4-his(3',4'-dimethylphenyloxy)benzene. Hensen (melting point 69°C) was used.

The test results are shown in Table 1.

The surface of the ``JJ'' paper, which had been subjected to 1,000 degrees of hardening, was smoothed using a super calender, and adjusted so that the smoothness was 600 to 1000 seconds when measured with a smoothness meter. Regarding the thus obtained sample (20), measurement of recording sensitivity, measurement of color density of the uncolored area on the surface of the recording layer, color density of static color development at 70° C., and i4 whitening test were conducted according to the following methods.

In order to measure the recording sensitivity of - and , a Toyo Seiki thermal gradient tester was used to heat the sample for 100 m5 ec at a temperature of 120°C and a pressure of 2.5 kg/cd. Measured using RD-914. The measured value represents the recording sensitivity of the thermal recording paper. Further, 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.

1 carp pull 1 wa 1 degree yabetsu yodo In the above tester, temperature 70'C pressure 2.5 kg/c
The sample was heated for 5 seconds under +fl conditions, and the color density at that time was measured using the above densitometer, and this measured value represented the static color density of the sample.

For the IalEnL whitening resistance test, the above test machine was used at a temperature of 150'
Heat the sample at 40°C to develop color, and heat the printed part at 40°C at 290°C (2
1) It was left in an environment of %RH for 24 hours, and changes in the surface were observed and sensory evaluated as follows.

Good: No change observed in the colored printed area.

Defective: The surface of the colored printed area appeared powdery, and so-called whitening was observed.

The test results are shown in Table 1.

Table 1 (22) As is clear from Table 1, Examples 1 to 3 according to the present invention
All of the thermal recording papers have poor recording sensitivity, whiteness,
It had static non-coloring property and whitening resistance. However, other comparative thermal recording papers had poor recording sensitivity (Comparative Examples 1 and 2).
．． 5.6.7.8), poor whiteness (Comparative Example 4), excessive static color development (Comparative Example 4.9), and easy whitening (Comparative Example 3)
) had the following drawbacks.

(Effects of the Invention) The heat-sensitive recording material of the present invention contains a new thermofusible abrasive material, has excellent high-speed recording suitability, has high whiteness, does not induce undesirable phenomena such as whitening, and has a high quality quality. It has extremely well-balanced properties and is of extremely high practical value.

(23) hand Continued sleeve Positive harm (spontaneous) 1999 1 October Ke [Three I

Claims (1)

[Claims] 1. A sheet-like support, a colorless to light-colored dye precursor formed on at least one surface of the sheet-like support, and a dye precursor that reacts with the dye precursor under heating. In a heat-sensitive recording material having a heat-sensitive color-forming layer containing a color developer that develops the color, the heat-sensitive color-forming layer further has the following general formula (I): ▲Mathematical formula, chemical formula, table, etc.▼(I) (However, , in the formula, R^1 to R^9 each independently represent a hydrogen atom or a methyl group, at least two of R^1 to R^5 represent a methyl group, and R^2, R
Any two of ^3 and R^4 represent a methyl group. ) A thermosensitive recording material characterized by containing at least one kind of aromatic ether compound represented by: