JPH02131986A - Heat sensitive recording material - Google Patents

Abstract

PURPOSE:To obtain high skin whiteness, excellent coloring density and coloring sensitivity by employing high purity bissulfide as developer, adding sulfosuccinates into a heat sensitive coloring layer, and employing carboxyl group modified polyvinylalcohol as binder. CONSTITUTION:In a heat sensitive recording material having a heat sensitive coloring layer which contains high purity bis(4-hydroxy-3-methylphenyl)sulfide represented by a formula (I) as colorless or pale electron donating coloring substance and electron acceptive developer, sulfosuccinates and carboxyl group modified polyvinylalcohol are contained in the coloring layer. The sulfosuccinates are of dioctylsulfosuccinates represented by a formula (II). The adding amount is 0.005-0.2 pts.wt. to 1 pt.wt. of coloring substance, and the polyvinylalcohol is 0.2-3 pts.wt. to 1 pt.wt. of the coloring substance.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a heat-sensitive recording material, and furthermore,
V L < indicates an f5 thermal recording material which has little background coloring and is rich in coloring characteristics. <<Prior art>> (Problems to be solved by the invention) Recording materials that utilize the coloring phenomenon caused by contact between an electron-donating color-forming substance and an electron-accepting color developer include, for example, pressure-sensitive recording paper, Thermal recording paper, thermal copying paper, etc., came into wide use with the progress of streamlining office work. Conventionally known dye-colored thermal recording paper, which uses triphenylmethane dyes or leuco bases of fluoran dyes as color-forming substances, is suitable for applications such as high-speed facsimiles and POS labels, for which demand has rapidly expanded in recent years. For,
Further improvement in thermal response is required. In order to improve thermal responsiveness to a single level, methods such as the use of low-melting point toning agents, addition of sensitizers, atomization of color-forming substances or coloring agents, and improvement of the smoothness of the recording paper surface have been used. ing. However, as the recording sensitivity increases, the whiteness of the background decreases, which is the so-called ra'+ problem of background strength blurring, and in order to prevent this, methods such as improving the whiteness of the background using additives have been adopted. There is. However, this method is not necessarily suitable for achieving the original purpose, as the color development sensitivity and maximum color development density decrease due to the influence of additives. In view of these circumstances, the present applicant has previously developed a high-purity bis(4- Completed a technology using hydroxy-3-methylphenyl sulfide as a color developer and applied for a patent. (
Patent Application 1983-147 When the above color developer is combined with a specific dye, it exhibits excellent performance that could not be obtained with conventional combinations of color-forming substances and color developers. If it is used in combination with a high-quality dye, problems with blurring of the background will still occur, resulting in a heat-sensitive recording material with low whiteness. In addition to the above-mentioned method, there is also a method using WIL acid ester salt type and/or sulfonate type surfactant as a dispersant for leuco dye (Japanese Patent Application Laid-Open No. 166096/1983), and a suitable amount of carboxyl group-modified polyvinyl alcohol as an additive. There are known methods of adding bis(4-hydroxy-3-methylphenyl) sulfide to a coloring agent. In either case, the effect was small and the problem of background blurring could not be solved.2 It was difficult to obtain a heat-sensitive recording material with excellent whiteness. As mentioned above, the inventors used high-purity bis(
When using 4-hydroxy-3-methylphenyl (4-hydroxy-3-methylphenyl) sulfide, there is no decrease in background whiteness, color density, or color sensitivity that occurs when combined with highly versatile leuco dyes, and the product can be used as a recording sheet. We have conducted extensive research into valuable heat-sensitive recording materials. As a result, in a heat-sensitive recording material provided with a fever coloring layer containing the color-forming substance and a tinting agent, when a sulfosuccinate is added to the heat-sensitive coloring layer and carboxyl group-modified polyvinyl alcohol is used as a binder, It was discovered that a heat-sensitive recording material with high background whiteness and sufficient color density and color sensitivity can be obtained, and the present invention was achieved. The sulfosuccinates used in the present invention can produce great effects when added at the time of preparing a dispersion containing a color-forming substance, as shown in Examples below. The reason for this is not clear, but it may be because the additive dissolves in the leuco dye and raises the eutectic point during color development, or it may be because the additive dissolves into the leuco dye, raising the eutectic point during color development, or because the color development reaction and color decolorization reaction between the leuco dye and the color developer occur. It is thought that the compatibility of the additive has the effect of biasing the reaction toward the decolorizing reaction side. The sulfosuccinates used in the present invention are used in the form of sodium, potassium, or ammonium salts,
The amount added is 0.005 to 1 part by weight of the color-forming substance.
0.02 parts by weight, preferably 0.01 to 0.1 parts by weight
Use within the scope of the section. If the amount added is less than 0.00511 parts by weight, no effect will be obtained, and if it exceeds 0.02 parts by weight, adverse effects such as a decrease in background whiteness will occur. In the S thermal recording material of the present invention, the carboxyl group-modified polyvinyl alcohol used as a binder for forming the thermosensitive coloring layer includes fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, and anhydrous polyvinyl alcohol. Binders used in -a include those made by reacting carboxylic acids such as itacon litl, or those made by saponifying polymers of vinyl #acid and unsaturated carboxylic acids such as maleic acid, fumaric acid, and itaconic acid. Polyvinyl alcohol, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, styrene maleic acid copolymerization polyacrylic acid, polyacrylamide, styrene
It can also be used in combination with synthetic polymers such as butadiene rubber latex, natural or modified natural polymers, etc. The amount of carboxyl group-modified polyvinyl alcohol to be used is preferably 0.2 to 3 parts by weight (in terms of solid content) per 1 part by weight of the color-forming substance. If the amount used is less than 0.2 parts, the effect will not be apparent and sufficient whiteness will not be obtained. Also, 3
Even if you use more than that part by weight, you will not get the corresponding effect. There are no particular restrictions on the method of adding the binder, as long as it is included in at least one of the dispersions shown in Examples below. As the color-forming substance used with the recording material of the present invention, various electron-donating dyes that develop color by melting reaction with a coloring agent are used, and specific examples thereof include 3-ethyl iso-amyl-6- Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-methyl cyclohexylamino-
6-Methyl-7-ayurinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl-p-}lylamino-6- Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7(
p-tert-butylanilino》fluorane, 3-diethylamine-6-methyl-7-chlorofluoran,
3-diethylamino-7-dibenzylaminofluorane, 3-cyclohexylamino-7-cyclofluorane, 3-diethylamino-7-methylfluorane, 3
-dibutylamino-7<<0-chloroanilino>>fluoran, 3diethylamine-7(0-chloroanilino)fluoran, 3.3゛-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide [crystal violet lactone], 3.3′-bis(4-dimethylaminophenyl)phthalide [malachite green lactone], 1. 3. 3-trimenalindolino 6゛-chloro-8゜-methoxypenzos birobilane,
3-(4-diethylamino-2-ethoxyphenyl)
Examples include -3- (1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 1-lis-4-dimethylaminophenylmethane, and the like. First, the sulposuccinate of the present invention is dissolved in water together with a color-forming agent, a known sensitizer (such as parabenzyl biphenyl, stearic acid amide, etc.), and a binder. A dispersion is prepared by thoroughly mixing or pulverizing the color developer with the pigment, additives, and binder in water. In either case, It is desirable that the dispersed particles be ground in advance using a grinder such as a ball mill into particles as small as possible, specifically to a particle size of 1 micron or less.The resulting dispersion is placed on a support such as paper. A heat-sensitive recording sheet is produced by coating and drying.It is common to mix the two dispersions and coat the mixture on the support, but it is also possible to coat the two dispersions separately in two separate coats. The amount of sulfosuccinates and binder to be used for color-forming substances differs depending on their combination or the combination of color developer, sensitizer, etc., so it cannot be stated unconditionally, but as mentioned above, it is usually color-forming. 0.0 sulfosuccinate head per 1 part by weight of substance
05 to 0.2 parts by weight, preferably 0.01 to 0.1 parts by weight, and the binder is preferably used in the range of 1 to 3 parts by weight (in terms of solid content). When producing the heat-sensitive recording sheet of the present invention, organic or organic pigments such as talc, kaolin, titanium oxide, calcium carbonate, zinc oxide, urea-formaldehyde resin, talc, kaolin, titanium oxide, calcium carbonate, urea-formaldehyde resin, etc. Water-soluble binders or crosslinking accelerators with crosslinking properties, protein adhesives and water-resistant additives such as glutaraldehyde, animal waxes such as beeswax and shellac wax, vegetable waxes such as carnauba wax, petroleum wax, and paraffin. Synthetic waxes such as microcrystalline wanox with hooks, polyethylene wax, metal soaps such as calcium stearate and zinc stearate (lubricants such as higher fatty acid gold [1], pressure coloring inhibitors, various surfactants, antifoaming agents, etc.) together with
It can also improve coating suitability and properties of recording sheets. (Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples. The method for producing the heat-sensitive recording sheet used in the examples and the measurement method for various color development characteristics, background whiteness, etc. were performed by the methods described below. (1) Method for producing a heat-sensitive recording sheet. (Parts are by weight. (A) Liquid Color-forming substance 53 parts Sulfosuccinates 0.1 part Binder (10 parts)
wt aqueous solution 1 29.2 parts parabenzylbiphenyl 106 parts CB) liquid bis(4-hydroxy-
8.0 parts (3-methylphenyl) sulfide binder (Own aqueous solution) 29.2 parts Calcium carbonate 8.0 parts Zinc stearate 0.8 parts Total 100.0 parts Both [A) and CB] having the above composition were separately prepared. A dispersion was prepared by dispersing it in a paint shaker. 1 part by weight of liquid (A) obtained as above and (B)?
j! Mix 21i parts again in a paint shaker,
This was coated on high-quality paper to a dry coating amount of 5 to 6 gems and dried to prepare a heat-sensitive recording sheet. (2) Method for measuring background whiteness and coloring characteristics of a heat-sensitive recording sheet. a. Background Immediately after preparing the whiteness recording sheet, the background whiteness was measured using a Macbeth reflection densitometer (RD-914, manufactured by Macbeth Co., Ltd.).b. was used to develop color by contacting it with a metal block having a temperature gradient of 60 to 130°C for 5 seconds at a pressure of 06kgLC.After color development, a Macbeth reflection densitometer was used to measure the color density and color temperature. C. Maximum color density The metal block mentioned above was heated to 200℃, and the pressure was 0.
．． Color was developed by contacting with 6 kg/c 2 for 3 minutes.
After color development, the density was measured using the method described above. Examples 1 to 4 A 10% by weight aqueous carboxyl group-modified polyvinyl alcohol solution (trade name: K.L-318 manufactured by Kuraray) was used as a binder for both liquids (A) and CB (solid content equivalent to 1 part by weight of color-forming substance). (1.65 parts by weight used), 0.03 parts by weight of sulfosuccinates were added to 1 part by weight of the color-forming substance, and bis(4-hydroxy-3
-methylphenyl) sulfide (tilt point 123.
9 to 124.5°C) in combination with various color-forming substances shown in Table 1 to prepare a fever recording sheet 1. The fabrication method is as described above. Table 2 shows the evaluation results of the obtained heat-sensitive recording sheet. Examples 5 to 8 (10% by weight instead of 10% by weight carpoxyl group-modified polyvinyl alcohol aqueous solution as binder for Buff)
Volivinyl alcohol water i? Ii was used, the ratio of carboxyl group-modified polyvinyl alcohol in the total binder was set to 33.3%, and the other conditions were as follows. A heat-sensitive recording sheet was produced under the same conditions as 41-4. Comparative Examples 1 and 2 A thermosensitive recording sheet was produced under the same conditions as in Example 1.2, except that sodium dioctyl sulfosuccinate was not added to (A) fl and a 10% by weight polyvinyl alcohol aqueous solution was used as the binder. Comparative Example 3.4 (A). (B) 10 as a binder for both liquids! t1
A thermal recording sheet was prepared under the same conditions as in Examples 1 and 2, except for using a % polyvinyl alcohol aqueous solution. Comparative Example 5.6 A thermosensitive recording sheet was produced under the same conditions as in Examples 1 and 2, except that sodium dioctyl sulfosuccinate was not used. (Effect of the invention) Conventionally, when high-purity bis(4-hydroxy-3-methylphenyl) sulfide is used as a coloring agent, there are only a limited number of color-forming substances that can be used at the same time. It has been difficult to obtain an S thermal recording material with excellent coloring properties and little coloring. However, by adding sulfosuccinates to the heat-sensitive coloring layer and using hydroxyl group-modified polyvinyl alcohol as a binder, the above-mentioned drawbacks that were seen when using highly versatile leuco dyes as coloring substances are eliminated. As a result, we were able to obtain a heat-sensitive recording material with high background whiteness and excellent color development properties. Due to this effect, it is thought that the use of bis(4-hydroxydi-3-methylphenyl) sulfide as a coloring agent will further expand in the future, and will greatly contribute to the industry. Applicant: Yuji Masuda, Representative of Steel Chemical Industry Co., Ltd.

Claims (5)

[Claims] (1) A heat-sensitive coloring layer containing a colorless or light-colored electron-donating color-forming substance and high-purity bis(4-hydroxy-3-methylphenyl) sulfide represented by formula (I) as an electron-accepting color developer. A heat-sensitive recording material having excellent background whiteness and color-forming properties, characterized in that the heat-sensitive color-forming layer contains a sulfosuccinate and a carboxyl group-modified polyvinyl alcohol. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (2) The heat-sensitive recording material according to claim 1, wherein the high purity bis(4-hydroxy-3-methylphenyl) sulfide has a melting point of 123.9 to 124.9°C. (3) The heat-sensitive recording material according to claim (1), wherein the sulfosuccinate is a dioctyl sulfosuccinate represented by formula (II). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (4) The heat-sensitive recording material according to claim (1), wherein 0.005 to 0.2 parts by weight of sulfosuccinates are added to 1 part by weight of the color-forming substance. (5) The heat-sensitive recording material according to claim (1), wherein 0.2 to 3 parts by weight of carboxyl group-modified polyvinyl alcohol is added to 1 part by weight of the color-forming substance.