JPH02122980A - Thermal recording material - Google Patents

Abstract

PURPOSE:To contrive higher brightness and higher high-speed recordability by incorporating a specified organic compound having an acetylacetoxyl group in a thermal color forming layer of a thermal recording material. CONSTITUTION:An organic compound having an acetylacetoxyl group of formula I or II, wherein R is an alkyl, aryl or aralkyl, is incorporated as a heat-fusible substance. When at least one compound of formula I or II is incorporated in a color forming layer of a thermal recording material, the color forming sensitivity of the recording material can be enhanced because the compound itself has a capability, even though weak, of developing a basic leuco dye into a color. The amount of the at least one compound used is 10-1000wt.% based on a color developer.

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]

Thermosensitive recording materials that utilize a heated color-forming reaction between normally colorless or light-colored leuco dyes and phenols or organic acids have been published in Japanese Patent Publication No. 43-4160, Japanese Patent Publication No. 14039-1973, Japanese Patent Publication No. 27736-1977, 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. There is.

Especially a heat-sensitive recording medium like this? The thermal facsimile machines, thermal printers, etc. that are used have been improved and are now capable of high-speed printing and high-speed image formation, which was previously 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 need, many of which involve the use of basic dye and color former combinations in combination with thermofusible substances.

When a heat-sensitive recording material containing such a thermofusible substance is heated, the thermofusible substance first melts, which dissolves the dye and color developer, causing the two to mix at the molecular level and cause a coloring reaction. is induced. Therefore, these thermofusible substances must have an appropriate melting point (preferably 60 to 140 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, these thermofusible substances should be mixed with water.
Is it desirable to have extremely low solubility, and also have properties such as low sublimation? It is desirable to have one. In the latter case, the heated colored part of the heat-sensitive recording material turns into powder over time? It is thought that this phenomenon is closely related to the so-called whitening phenomenon, which causes a wispy appearance, and is an extremely important property for the practical use of thermosensitive recording materials. Although many of these thermoplastic and strong materials have been proposed in the past, there are few that satisfy all of the above conditions, and new materials have been sought.

The present invention is a novel thermofusible substance used together with the aforementioned leuco dye and coloring agent. and apply it to a thermal recording medium to improve the recording sensitivity of the recording medium. Significantly improved and the quality of the islands involved in the record? The aim is not to reduce the

[Means for solving problems]

Is this the purpose of the inventors? In order to achieve (jJf Rk
As a result of stacking, as a thermofusible substance, general formula [I] or [II] (in the above formula, R represents an alkyl group, an aryl group, or an aralkyl group, and two or more compounds are used in the benzene ring, Compared to higher fatty acid amides such as stearic acid amide and palmitic acid amide, which have been proposed as thermofusible substances, it does not cause a decrease in whiteness and deteriorates the quality of colored images over time. It was discovered that extremely high recording sensitivity could be obtained without experiencing a phenomenon such as whitening, and the present invention was completed.

The present invention provides a thermosensitive recording material having a thermosensitive coloring layer that utilizes a coloring reaction between a colorless or monochromatic basic leuco dye and a coloring agent, in which the coloring layer of the thermosensitive recording material contains the general formula CI)
The thermosensitive recording material is characterized in that it contains at least one f compound represented by [■]. It is not clear why the specific thermofusible substances (hereinafter referred to as sensitizers) as mentioned above improve the color development sensitivity of the heat-sensitive recording material containing them, but these compounds themselves are also weakly Leuco dye? It is presumed that one of the 70 reasons is that it has n-hika that produces color. Whiteness again? The reason why it is not lowered is because it is resistant to water, so there is no record of bleaching etc.
Although there are very few phenomena that deteriorate image quality, it is thought that the low sublimation property is responsible for this, but the inventor does not adhere to this interpretation.

Specific examples of the sensitizers constituting the present invention include the following:
As shown in the reaction formula below, it can be synthesized more easily and in higher yields than the corresponding phenols and diketenes.

As mentioned above, the substituent R is a hydrocarbon selected from an alkyl group, an aralkyl group, and an aralkyl group. What if there are any more restrictions on R? The melting point of the compound of the invention is determined by the melting point of the compound of the invention. That is, in order to exhibit desirable performance as a sensitizer, the melting point of the compound constituting the present invention is required to be 60° C. or higher. As a result of systematic research, the present inventors have found that there is a correlation between the melting point and the amount of raw materials for the compound of the present invention. Admitted. That is, if the melting point of the starting phenol derivative or naphthol is below 80°C, the melting point of the acetylaceto s form produced will not reach a temperature preferable as a sensitizer. koσ)
There is no direct relation to the size of the substituent R.

For example, the invention mentioned above? Among the specific examples of the constituent compounds, p-tert, which is the raw material for (A), (B), and (D),
, octylphenol, p-phenylphenol and 2-naphthol have melting points of 83°C, 165°C and 121°C, respectively.

On the other hand, for example, as raw materials 2,4.6 trimethylphenol (melting point 72°C), p-cumylphenol (melting point 73°C)
, 0-phenylphenol (melting point: 59°C), their acetylacetated products all have a melting point of 59°C.
The temperature does not even reach 0°C, making it unsuitable as a sensitizer.

The thermofusible substance constituting the present invention may be used together with any one of compounds such as leuco dyes and coloring agents;
More than one species may be used in combination. Further, it can be used in combination with other sensitizers within a range that does not inhibit the desired effects of the present invention. The amount of the compound used in the present invention is preferably 10 to 1,000 times, preferably 50 to 300 times, relative to the color developer.

Compound of the Invention The heat-sensitive coloring layer used mainly consists of a coloring agent consisting of a leuco dye, a phenol or an organic acid, and the compound of the invention. Further, the coloring layer preferably contains an inorganic pigment, and may further contain waxes if necessary. Other of these ingredients? A binder to adhere to the support? Contains it as an essential ingredient.

As the leuco dye, conventionally known ones may be used, such as those shown below.

Crystal violet lactone, 3-(N-ethyl-
N-Isopentylamino)-6-methyl 7-anilinofluorane, 3-diethyl-epsilon-methyl-7-anilitofluorane, 3-diethylamine-6-methyl-7-
(o,p-zintylanilino]fluorane, :)-(N
-ethyl-p-toluidino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7
-anilinofluorane, 3-(N-cyclo-\xyl-N-methylamine)-6-methyl-7-anilinofluorane, 3-diethylamine-7-(0-chloroanilino)fluorane, 3-diethylamine-7 -(m-)lifluoromethylanilino)fluoran, 3-diethylamine-6methyl-7-chlorofluoran, 3-diethylamino-6-methylfluoran, 3-cyclohexylamino-6-chlorofluoran.

The coloring agent made of phenols or organic acids may be the same (conventionally known ones), and the following are examples thereof.

Bisphenol A% P-benzyl hydroxybenzoate,
n-butyl di(4-hydroxyphenyl)acetate, bisphenol S, 4-hydroxy, 4'-isopropyloxydiphenyl sulfone, 1.1-di(4-hydroxyphenylcyclohexane, 1.t-di(hydroxyphenylthio)) -3゜5-dioxahebutane.

Here, as a sensitizer that can be used in combination with the compound of the present invention, a thermofusible organic compound with a melting point of 50-150°C is used. This is an example.

p-hydroxynaphthoic acid phenyl ester, p-hensyl biphenyl, benzyl naphthyl ether, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, diphenyl carbonate, ditolyl carbonate, m-terphenyl, ethylene crico V.

7-m-) Lylether.

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

Furthermore, the coloring layer of the present invention may be made of various waxes. Obtain what is included as necessary. They may be paraffins, amide waxes, bisimide waxes, and known waxes such as higher fatty acids. Regarding the adhesive, polyvinyl alcohol of various molecular weights, starch and its derivatives, cellulose derivatives such as methoxycellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylate/acrylic acid, etc. Acid ester copolymer, acrylic amide/acrylic ester/tutaacrylic acid ternary copolymer, styrene/! In addition to water-soluble polymers such as octahydric maleic acid copolymer alkali salt, polyacrylamide, nodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic ester, Latex such as beer chloride/vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinegar [vinyl copolymer, methyleneno/butadiene/acrylic copolymer? Can be used.

A mixture of these materials that develops color when heated, paper, coated paper whose surface is coated with clay, plastic, etc., and synthetic paper made mainly from plastic, which is coated on a plastic film. , heat-sensitive recording material. Coating amount +1, 1 when the coating layer is dry
~lOg/rr? is preferable, and 2 to 7 g/- is particularly preferable.

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. Note that the numbers represent parts by weight unless otherwise specified.

〔Example〕

Synthesis Example 1 25.5 g of p-phenylphenol and 13.0 g of diketene; 160ffi7! of tetrahydrofuran (I'
HF) and add a few drops of pyridine there. After an induction period of several minutes σ), an exothermic reaction occurs. After standing for one day, crystals were formed from the solution. The crystals were separated by filtration and recrystallized from THF to obtain white crystals 29. Og & got it.

As a result of mass spectrometry and nuclear magnetic analysis, is it the desired compound [B]? confirmed.

Synthesis Example 2 144g of 2-naphthol and 9.0gσ] diketene? 5
Dissolve 0ml of Tl4FK and add a few drops of σ]pyridine to it. After an induction period of several minutes, an exothermic reaction takes place. After leaving it for one day, 'rHF Y was distilled off and a yellow solid was formed. Obtained. This solid? Recrystallization from toluene gave 5.7 g of white crystals. As a result of mass spectrometry and nuclear magnetic resonance analysis, target compound [D]
To be? confirmed.

Example 1 ■ Dispersion flLA preparation 3-(N-Isopentyl-N ethylamino)-6-methyl-7-anilitunluorane polyvinyl alcohol 1
0%71 10 water
70 This composition was ground with a sand grinder to an average particle size of 1fn1.

■Dispersed B-tone 4.4'-Impropylidenediphenol Compound of the present invention (B-10 Phenyl alcohol 1
0%M 10 water
70 This composition was ground to an average particle size of 1 μm using a sand grinder.

■ Preparation 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% nocilafine dispersion, and 180 parts of a 10% polyvinyl alcohol aqueous solution were mixed and stirred to prepare a coating liquid.

The coating amount after drying on this coated 1'1%'50 g/m' base paper is 7.5 g/rr? Is it coated and dried on thermal recording paper? Obtained.

Example 2 ■ Pigment undercoated paper] Preparation: 85 parts of fired Ray (trade name: Ancilesox) and 320 parts of water.
20 parts of styrene-pukudiene copolymer emulsion (solid content 50 parts) was added to the resulting dispersion, and 10% oxidized starch aqueous solution was added to the resulting dispersion. 48g of the coating liquid obtained by mixing 50 parts/
The amount of coating after drying on a base paper of 7.0 g/?yI!
A pigment-primed paper was obtained by applying a VC coating.

■ Formation of coloring layer 50 parts of dispersion A, 200 parts of dispersion B, 2 parts of calcium carbonate
5 parts, 30 parts; 20 parts of rough-in dispersion and 180 parts of 10% polyvinyl alcohol aqueous solution were mixed and stirred to prepare a coating liquid. After drying, apply the obtained coating liquid to the pigment undercoated paper.
] Apply and dry so that the coating amount is 5.0 g/yy+', and then apply it to thermal recording paper. Obtained.

Example 3 In the preparation of B'gJL, compound (0) was used instead of compound (B) of the present invention? Thermal recording H1? was made in the same manner as in Example 2 except that it was used. Obtained.

Comparative Example 1 A thermosensitive recording paper was prepared in the same manner as in Example 1 except that stearic acid amide was used instead of the compound of the present invention CB)σ] in the preparation of liquid B. Obtained.

Comparative Reli 2 In the preparation of liquid B, instead of the compound (B) of the present invention,
Stearic acid amide? A thermosensitive recording paper was obtained in the same manner as in implementation ful 12 except that the following was used.

Comparative Example 3 A thermosensitive recording paper was obtained in the same manner as in Example 2, except that 1-hydroquine-2-naphthoic acid benzyl ester was used in place of the compound (B) of the present invention in liquid B and ¥LJ.

The surface smoothness of the six types of thermal recording paper obtained as described above is determined by the supercalendar ζ? Processing was performed so that the smoothness measured with a Beck smoothness meter was 600 to 1000 seconds. 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.

The recording sensitivity was measured at a temperature of 12
Heating a lOOm5ec sample at 0°C and a pressure of 2.5 Kq/crl, the color density at that time? Recording sensitivity of thermal paper measured with Macbeth RD-914? A representative value was used.

The density of the uncolored area (blank area) of the recording paper was measured with a dosimeter, and the value was taken as a representative value of whiteness.

Does whitening occur when the sample is tested at a temperature of 150°C using the tester mentioned above? After color development, the color development area was left in an environment of 40° C. and 90% for 24 hours, and the surface change was sensually evaluated.

In the table, ○ means that no change is observed in the colored printed area? Is the printed surface powder? This indicates that so-called whitening has occurred.

Table 1 [Effects of the Invention] As described above, since the heat-sensitive recording material of the present invention uses a new thermofusible material, it has excellent high-speed recording suitability, good whiteness, and no whitening problem. It does not induce any undesirable phenomena and has extremely balanced properties in terms of quality.

Claims (1)

[Scope of Claims] A thermosensitive recording material having a thermosensitive coloring layer that utilizes a coloring reaction between a colorless or light-colored basic dye and a coloring agent, wherein the thermosensitive coloring layer contains a compound of the general formula [I] or [ II] ▲There are mathematical formulas, chemical formulas, tables, etc.▼[I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼[II] (In the above formula, R represents an alkyl group, an aryl group, or an aralkyl group, and there are two A thermosensitive recording material characterized by containing at least one organic compound having an acetylaceto group represented by the following formula.