JPH04358881A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a thermal recording material, in which there is no printing trouble in continuous printing, by improving the recording sensitivity and shelf stability of the thermal recording material. CONSTITUTION:In a thermal recording material utilizing the heat-sensitive color development reaction of a dye precursor and a developer through an undercoating layer containing a plastic pigment on a supporter, a high molecular emulsion containing benzyl alcohol and/or 2,2,4-trimethyl-1,3- pentanediolmonoisobutylate as a film formation assistant is comprised in the undercoating layer.

Description

Description: FIELD OF INDUSTRIAL APPLICATION This invention relates to a heat-sensitive recording material. More specifically, the present invention relates to a heat-sensitive recording material that has excellent recording sensitivity and storage stability, and is free from printing failure during continuous printing. [0002] Thermal recording method has been highly praised for its advantages, such as being able to obtain colored images simply by heating, and the ability to make this recording device relatively simple and compact. It is widely used as a recording method. [0003] Particularly in recent years, improvements have been made in facsimile printers that use such heat-sensitive recording methods, and high-speed recording, which was previously considered difficult, has become possible. As the speed of such devices increases, the heat-sensitive recording materials used therein are required to further improve the recording sensitivity, and many proposals have been made in this regard. [0004] In order to improve the recording sensitivity of a heat-sensitive recording material, the heat insulating properties of the base material of the heat-sensitive recording material are considered important. Therefore, hydrophobic organic polymer compound particles having lower thermal conductivity than inorganic pigments are included in the undercoat layer (Japanese Patent Laid-Open No. 59-171
685, JP-A No. 60-2397), and in order to further add air insulation, fine particles of a hollow organic polymer compound are included in the undercoat layer (JP-A-59-1716).
No. 85, Japanese Unexamined Patent Publication No. 59-225987), etc. have been proposed. However, when fine particles of these organic polymer compounds (plastic pigments) are contained in the undercoat layer, they have poor affinity with the heat-sensitive coloring layer, and the insulating properties of the undercoat layer do not require the use of conventionally used inorganic pigments. Since the temperature is higher than that of the undercoat layer, the temperature rise at the interface between the heat-sensitive coloring layer and the undercoat layer due to heating during printing also increases. [0006] Due to these causes, the adhesion between the heat-sensitive coloring layer and the undercoat layer tends to decrease, so there is a drawback that the heat-sensitive coloring layer is likely to peel off during printing, which is a problem in printing. SUMMARY OF THE INVENTION As described above, conventional heat-sensitive recording paper provided with an undercoat layer containing plastic pigments has the drawback that although the recording sensitivity is improved, printing problems are likely to occur. The present invention solves this problem and provides a thermal recording paper which has high recording sensitivity and is free from printing problems. [0009] The above objects of the present invention are achieved by using a binder containing a specific film forming aid in the undercoat layer. The present invention relates to a heat-sensitive recording material in which a heat-sensitive coloring layer is provided on at least one side of a support via an undercoat layer containing a plastic pigment, and the undercoat layer utilizes a heat-sensitive coloring reaction between a dye precursor and a color developer. It is characterized in that it contains a polymer emulsion containing benzyl alcohol and/or 2,2,4-trimethyl-1,3-pentanediol monoisobrate as a film-forming agent. The plastic pigments used in the present invention include polystyrene, polystyrene derivatives, crosslinked products such as diisobutylene-maleic anhydride copolymers, phenol-formaldehyde resins, polyurethane resins, polyester resins, polycarbonate resins, polymethyl methacrylate, Fine particles of polyvinyl chloride, polyvinylidene chloride, urea-formaldehyde resin, benzoguanamine resin, etc. and having a particle size of 0.05 to 5 μm are preferably used. In addition, for the purpose of improving the heat insulation properties and lees absorption properties of the undercoat layer, plastic pigments having a hollow, porous, or doughnut-like shape can be used as appropriate.One or more types selected from these plastic pigments can be used as appropriate. Use as a pigment for the undercoat layer. [0011] In the present invention, various polymer emulsions are used as the binder for the undercoat layer, examples of which include styrene/butadiene copolymers, styrene/acrylic acid copolymers, and styrene/acrylic ester copolymers. copolymer,
Examples include various emulsions such as acrylonitrile-butadiene copolymers, vinylidene chloride copolymers, and vinyl acetate copolymers. It is desirable that the binder for the undercoat layer has a high glass transition temperature. If the glass transition temperature is low, the undercoat layer itself will melt due to heating during printing, resulting in printing problems. However, polymer emulsions with a high glass transition temperature have a high minimum film-forming temperature and deteriorate film-forming properties, making it impossible to form a uniform film.As a result, the affinity between the heat-sensitive coloring layer and the undercoat layer is poor. There is a drawback that printing errors are more likely to occur as a result. Therefore, in the present invention, by adding a film-forming aid to the above-mentioned resin, it is possible to lower the film-forming temperature and form a uniform film, thereby making it possible to produce a heat-sensitive recording material free from printing defects. became. As a film-forming agent, benzyl alcohol and/or 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (3-hydroxy-2,2,4
-trimethylpentyl isobutyrate). Glycol ethers such as monoalkyl ether of ethylene glycol and monoalkyl ether of diethylene glycol, which are commonly used as film-forming aids, have a great effect on improving film-forming properties, but they have the disadvantage that they cause the heat-sensitive coloring layer to develop color and cause background fogging. There is. Furthermore, dicarboxylic acid esters such as dibutyl phthalate and dioctyl phthalate remain in the undercoat layer even after the undercoat layer is applied and dried, so they have problems such as inhibiting color development of the heat-sensitive coloring layer and fading the color image. there were. [0017] Benzyl alcohol and 2,2,4-trimethel-1,3-pentanediol monoisobutyrate have been found to be effective as substances that do not cause such problems and are highly effective as film-forming aids. I found a headline. In the present invention, the coating aid is contained in an amount of 2 to 40% by weight, more preferably 5 to 20% by weight, based on the solid content of the polymer emulsion. If the content is too low, the film forming properties will be insufficient, and if the content is too high, the colored image will easily fade. The undercoat layer may contain inorganic pigments other than plastic pigments, such as zinc oxide, titanium dioxide, calcium carbonate, magnesium carbonate, barium sulfate, clay, talc, calcined clay, silica, magnesium silicate, etc. can be mentioned. [0020] The particle size is preferably 2 μm or less, and the blending amount is 30 μm or less for the plastic pigment.
% or less. If the amount exceeds this range, the heat insulation properties of the undercoat layer will decrease, resulting in a decrease in sensitivity. [0021] In addition to the above-mentioned polymer emulsion, the undercoat layer may be combined with a water-soluble polymer substance known as an adhesive. Specifically, for example, the following may be mentioned. Polyvinyl alcohol, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, starch, starch derivatives, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyamide, etc. can be mentioned. The blending ratio of the pigment and adhesive in the undercoat layer of the present invention is arbitrarily determined depending on the selected components, and is generally preferably between 20:1 and 1:1. [0024] When forming this undercoat layer, the coating amount is generally 1 to 15 g/m2 (dry weight), and the coating is easy by applying it onto the support using an ordinary coating machine. However, it is preferable to use a coating method such as a blade or a slit die that can form a coating layer with good surface properties. [0025] On the undercoat layer thus formed,
A heat-sensitive recording layer is formed, and the recording layer is formed by a conventional method. Dye precursors used in the present invention include:
There is no particular restriction as long as it is used for general pressure-sensitive recording paper, heat-sensitive recording paper, etc. Specific examples include: (1) As a triarylmethane compound, for example, 3,
3-bis(P-dimethylaminophenyl)-6-dimethylaminophthalide and the like. (2) As a diphenylmethane compound, for example, 4,4
'-bis-dimethylaminobenzhydrin benzyl ether, N-2,4,5-trichlorophenylleukoolamine, etc. (3) As a xanthene compound, for example, rhodamine B
-anilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-butylaminofluorane, 3-diethylamino-7-(2-
chloroanilino)fluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl-7-anilinofluorane, 3-cyclohexyl-methylamino-6-methyl-7-anilinofluorane Linofluorane, 3-diethylamino-6-chloro-7-(
β-ethoxyethyl)aminofluorane, 3-diethylamino-6-chloro-7-(γ-chloropropyl)aminofluorane, 3-dibutylamino-6-methyl-7-
Anilinofluorane, 3-(N-isoamyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3
-ethyl-isoamylamino-6-methyl-7-anilinofluoran, 3-dibutylamino-7-chloroanilinofluoran, and the like. These dye precursors can be used alone or in combination of two or more, and are appropriately selected and used depending on the purpose and desired properties of the heat-sensitive recording material. As the color developer used in the present invention, phenol derivatives and aromatic carboxylic acid derivatives are preferred, and bisphenols are particularly preferred. To specifically illustrate this, examples of phenols include p-octylphenol, p-tert-butylphenol, p-phenylphenol, 2,2-bis(p-hydroxyphenyl)propane, and 2,2-bis(
p-hydroxyphenyl)pentane, 1,1-bis(p
-hydroxyphenyl)hexane, 2,2-bis(p-
hydroxyphenyl)hexane, 1,1-bis(p-hydroxyphenyl)-2-ethylhexane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl Sulfone, 4-hydroxy-4'
-isopropyloxydiphenyl sulfone, bis(3-
Examples include allyl-4-hydroxyphenyl) sulfone. Further, as the aromatic carboxylic acid derivative, p
-Hydroxybenzoic acid, butyl p-hydroxybenzoate, 3,5-di-tert-butylsalicylic acid, 3,5-
Examples include di-α-methylbenzyl salicylic acid and polyvalent metal salts of the above carboxylic acids. The blending ratio of the dye precursor and color developer is not necessarily limited and is adjusted depending on the materials used, but is generally 1 to 1 part by weight of the dye precursor.
10 parts by weight of color developer are used, preferably 1.5 to 5 parts by weight. These dye precursors and color developers are generally processed into polyacrylamide, polyvinylpyrrolidone, and polyvinyl by using various wet mills such as ball mills, coball mills, attritors, vertical and horizontal sand mills, etc., using water as a dispersion medium. After being dispersed with alcohol, methyl cellulose, a water-soluble synthetic polymer compound such as styrene-maleic anhydride copolymer salt, and other surfactants to form a dispersion liquid, it is used in the preparation of heat-sensitive coloring paints. In the present invention, other materials constituting the heat-sensitive recording layer include adhesives, sensitizers, inorganic or organic pigments,
Examples include waxes, metal soaps, and if necessary, ultraviolet absorbers, storage stabilizers, fluorescent dyes, and coloring dyes. Water-soluble adhesives are generally used, such as polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, ethylene-maleic anhydride copolymer salt, styrene-maleic anhydride copolymer salt, Examples include diisobutylene-maleic anhydride copolymer salt, styrene-acrylic acid copolymer salt, polyacrylic acid, starch, starch derivatives, casein, and gelatin. [0035] In addition, for the purpose of imparting water resistance to these binders, a water resistance imparting agent may be added, or a hydrophobic emulsion,
Specifically, styrene-butadiene rubber lux, acrylic resin emulsion, etc. can also be added. Sensitizers include fatty acid amides such as stearamide, ethylene bisstearamide, methylolbehenic acid amide, and palmitic acid amide, p-benzylbiphenyl, dibenzyl terephthalate, and 1-hydroxy-2-naphthoic acid. Phenyl, dibenzyl oxalate, di-p-chlorobenzyl oxalate, di-p-oxalate
Methylbenzyl, di-o-chlorobenzyl adipate,
1,2-di(3-methylphenoxy)ethane, 1,2-
In addition to bis(3,4-dimethylphenyl)ethane, various known thermofusible substances can be added. Inorganic pigments include calcium carbonate, kaolin, calcined kaolin, talc, waxite, diatomaceous earth, aluminum oxide, aluminum hydroxide, magnesium hydroxide, magnesia, silicon dioxide, titanium dioxide, barium carbonate, barium sulfate, and zinc oxide. Examples of organic pigments include urea, phenol, epoxy, styrene, nylon, polyethylene, melamine, and benzoguanamine resin. [0038] As the wax, paraffin wax,
Examples include carnauba wax, microcrystalline wax, polyethylene wax, and higher fatty acid ester wax. Examples of the metal soap include polyvalent metal salts of higher fatty acids, such as zinc stearate, aluminum stearate, calcium stearate, and zinc oleate. In the present invention, the heat-sensitive recording layer is formed by undercoating by known coating methods such as the air knife method, blade method, gravure method, roll coater method, spray method, dip method, bar method, and extrusion method. The coating layer is formed by coating and drying, and it is preferable to use a coating method that can form a coating layer with good surface properties, such as roll blade coating. [0041] The amount of the coating liquid to be applied is usually adjusted within the range of 2 to 12 g/m2, preferably 3 to 8 g/m2 in terms of dry weight. [0042] Also, the support is not particularly limited,
Papers such as high-quality paper, medium-quality paper, glossy paper, coated paper, art paper, cast-coated paper, synthetic paper, synthetic fiber paper, synthetic resin film, and laminates thereof are appropriately selected and used. . [0043] After forming the undercoat layer and the heat-sensitive recording layer, it is possible to perform surface smoothing treatment such as super calendering if necessary, and a coating layer may be provided on the back surface of the support for purposes such as curl control. etc. are also possible. [Examples] The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited thereto. Further, parts and % in the examples indicate parts by weight and % by weight, respectively. [Examples 1 and 2 and Comparative Examples 1 and 2] Formation of undercoat layer Polymer emulsions having the following compounding ratios were produced by emulsion polymerization to a concentration of 45%. Acrylonilolyl 65 parts Butyl acrylate 30 parts Methacrylic acid
3 parts hydroxyethyl methacrylate 2 parts Polymer emulsion A contains 10% by weight of benzyl alcohol based on the solid content of this polymer emulsion, and 2,2,4-trimethyl-1,3-pentanediol monoisobutyl Polymer emulsion B contains 10% by weight of dibutyl phthalate, and polymeric emulsion C contains 10% by weight of dibutyl phthalate.
Created as. For comparison, a polymer emulsion D without any film-forming aid added was used. The above four types of polymer emulsions A, B, C, and D were each prepared as an undercoat layer coating solution in the following formulations. (1) Preparation of undercoat layer coating liquid Urea-formalin resin fine particle dispersion liquid
200
(Yupal C125: manufactured by Mitsui Toatsu Chemical Co., Ltd.) Oxidized starch 20% aqueous solution

10 parts polymer emulsion (solid content 45%)

10 parts The above components were mixed to prepare a coating liquid for an undercoat layer. This undercoat layer coating liquid is
It was coated and dried on the felt side of high-quality paper of g/m2 using a blade coater so that the coating amount after drying was 6 g/m2. Formation of heat-sensitive recording layer (1) Preparation of dye precursor dispersion 3-(N-ethyl-N-isoamylamino-6
-Methyl 20 parts
-7-anilinofluorane 10% polyvinyl alcohol solution
10 copies
water

40 parts This composition was ground using a vertical sand mill (manufactured by Imex Corporation, Sand Grinder) until the average particle diameter was 0.5 μm. (2) Preparation of color developer dispersion 2,2-bis(p-hydroxyphenyl)propane 10 parts p-
benzyl biphenyl
10 parts 10% polyvinyl alcohol solution

Part 10 Water

40 parts This composition was ground to an average particle size of 1.5 μm by the same method as the method for preparing the dye precursor dispersion. (3) Preparation of coating liquid for heat-sensitive recording layer To 40 parts of the above dye precursor dispersion and 160 parts of the color developer dispersion,
60 parts of calcium carbonate, 100 parts of 20% oxidized starch aqueous solution
A heat-sensitive recording layer coating solution was prepared by stirring and mixing 10 parts of a 30% zinc stearate dispersion, 10 parts of a 30% paraffin dispersion, and 50 parts of water. This coating solution was applied onto the undercoat layer using a rod blade coater so that the coating amount after drying was 5.0 g/m2, and dried to form a heat-sensitive recording layer, and smoothed using a super calender. A heat-sensitive recording material was produced. The recording sensitivity and recording suitability of the four types of heat-sensitive recording materials thus obtained were evaluated.
Recording sensitivity and recording aptitude were determined using the high-speed facsimile machine UF-60 manufactured by Matsushita Electric Transmission Co., Ltd. according to the Standard Chart N of the Institute of Image Electronics Engineers.
02 was printed and recorded, and the color density at that time was measured using a Macbeth densitometer RD-914 to obtain a value representative of the recording sensitivity of the thermosensitive recording paper, and at the same time, the recording suitability of the image was evaluated based on the presence or absence of printing problems. In addition, the storage stability is 4 for those printed with UF-60.
Evaluation was made based on the change in print density after being left for 24 hours in an atmosphere at 0°C and 90%. The results are shown in Table 1. [Table 1] [Effects of the Invention] By the method of the present invention, it has become possible to produce a high-quality heat-sensitive recording material that has excellent recording sensitivity and storage stability and is free from printing defects.

Claims (1)

[Claims] 1. A heat-sensitive recording material, comprising a heat-sensitive coloring layer that utilizes a heat-sensitive coloring reaction between a dye precursor and a color developer, provided on at least one surface of a support via an undercoat layer containing a plastic pigment. A heat-sensitive recording material characterized in that the undercoat layer contains a polymer emulsion containing benzyl alcohol and/or 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate as a film-forming agent.