JPS6046294A - Thermal recording material - Google Patents

Abstract

PURPOSE:To prevent electrostatic charges from being generated and contrive to enhance chemical resistance and head matching property, by a method wherein a protective layer comprising a water-soluble polymer, a filler and a conductive agent is provided on a thermal color forming layer comprising a leuco dye and a color developer as main constituents, and the surface resistance thereof is specified. CONSTITUTION:The protective layer comprising a water-soluble polymer, a filler and a conductive agent as main constituents is provided on the thermal color forming layer comprising a leuco dye, a color developer and auxiliary additives. The amount of the conductive agent used is so set that the protective layer has a surface resistance of not higher than 10<12>OMEGA. Accordingly, various troubles associated with electrostatic charging are prevented from occurring, reduction in sensitivity is suppressed, and image stability is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye and a color developer.

[Prior art]

It has been known for a long time that color-forming leuco dyes, which are usually colorless or light-colored, and organic acidic substances melt and react with each other when heated, producing color.An example of applying this color-forming reaction to recording paper is It is disclosed in Japanese Patent Publication No. 4160, Japanese Patent Publication No. 45-14039, etc., and is well known.

These thermal recording sheets are used in a wide range of fields, including measurement recorders, computer terminal printers, facsimile machines, automatic ticket vending machines, and barcode labels.Recently, these recording devices have become more diversified and more sophisticated. As the demand for heat-sensitive recording sheets increases, the quality required for heat-sensitive recording sheets also becomes higher. For example, as the speed of thermal heads increases, there is a demand for thermal recording sheets that can record high-density, clear images even with minute thermal energy and that have good head matching properties such as sticking and head dregs. Additionally, as speeds in the thermal facsimile field continue to increase, it has become common to drive the thermal head at high speeds, and static electricity is generated due to rough contact with the head and platen roll, causing problems such as paper jams to become more noticeable. In this type of technical field, there is a strong demand for improvements in dynamic coloring sensitivity as well as countermeasures against static electricity.

However, in this case, in addition to causing inconveniences such as images disappearing due to moisture during storage, when a conductive agent is added to the heat-sensitive coating solution, the heat-sensitive coating solution may condense or fog. This may cause problems such as

〔the purpose〕

The present invention prevents the generation of static electricity, overcomes the problem of paper feeding problems caused by static electricity, and improves chemical resistance and head matching without reducing sensitivity. The purpose is to provide an improved heat-sensitive recording material.

〔composition〕

According to the present invention, in a heat-sensitive recording material in which a heat-sensitive color forming layer containing a leuco dye and a color developer as main components is provided on a support, a water-soluble polymer, a filler and a conductive material are provided on the heat-sensitive color forming layer. A protective layer containing the agent is provided and its surface resistance is 101.
A heat-sensitive recording material characterized in that the resistance is 2Ω or less is provided.

The heat-sensitive recording material according to the present invention has a heat-sensitive coloring layer and a protective layer provided on a support, and these will be explained in detail below. The heat-sensitive color forming layer is mainly composed of a leuco dye and a color developer.The leuco dyes used in the present invention can be applied alone or in a mixture of two or more kinds. Heat-sensitive materials such as triphenylmethane, fluoran, phenothiazine, auramine,
Leuco compounds of spiropyran-based dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3.3-bis(p-dimethylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis(P- dimethylaminophenyl)-6-dibutylaminophenyl, 3.3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3.3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6- Chlorfluorane, 3-dimethylamino-5,7-dimethylfluorane, 3
-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6
-Methyl-7-chlorofluorane, 3-(N-p-tolyl-N-ditylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-(N-(3'-hlifluoromethylphenyl)amino)-6-dinithylaminofluorane, 2-(3,
6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, 3-diethylamino-7-(o-chloroanilino) ) fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane.

3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N,N-diethylamino)-5-methyl -7-(
N.

N-dibenzylamino)fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane, 3-(2'- 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy- 5'-nitrophenyl) phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl) phthalide, 3-(2'-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'
-methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-( N-benzyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluoran, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-( α-phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p-n
-butylanilino)fluorane, 3-(N-benzyl-N-cyclohexylamino)-5
, 6-penzo 7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
',5'-benzofluorane etc.

Further, as the color developer used in the present invention, various electron-accepting substances that react with the leuco dye and develop color when heated are used, and specific examples thereof include phenol as shown below. Examples include acidic substances, organic or inorganic acidic substances, and salts thereof.

gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di t,e
rt-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4'-isopropylidene diphenol, 4,4'-isopropylidene bis(2-chlorophenol), 4,4'-isopropylidene bis (2,6
-dibromophenol), 4,4'-isopropylidene bis(2,6-dichlorophenol), 4゜4'-isopropylidene bis(2-methylphenol), 4,4'
-isopropylidene bis(2,6-dimethimephenol), 4,4'-isopropylidene bis(2j; e r
j--butylphenol lidene diphenol, 4,4
'-Cyclohexylidene bisphenol, 4,4'-cyclohexylidene bis(2-methylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 3,
5-xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolac type phenolic resin, 2,2'-thiobis(4,6-
dichlorophenol), catecho-1ol, resorcinol,
Hydroquinone, pyrogallol, phloroglycine, phloroglycin carboxylic acid, 4-tert-octylcatechol, 2,2'-methylenebis(4-chlorophenol), 2,2'-methylenebis(4-methyl-6-7er)
t-butylphenol 2'-dihydroxydiphenyl,
Ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-hydroxybenzoic acid-p
-Chlorbenzyl, p-hydroxybenzoate-〇-chlorobenzyl, p-methylbenzyl P-hydroxybenzoate, n-octyl P-hydroxybenzoate, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2 -Hydroxy-6-naphthoic acid, 2-hydroxy-
Zinc 6-naphthoate, 4-hydroxydiphenylsulfone, 4-hydroxy-4'-chlorodiphenylsulfone, bis(4-hydroxyphenyl)sulfide, 2-hydroxy-p-toluic acid, 3,5-di-tert-butylsalicylic acid Zinc, 3.

tin 5-di-tert-butylsalicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, etc.

These color developers are usually used in an amount of 2 parts by weight per 1 part by weight of the leuco dye.
~6 parts by weight are used.

In the present invention, in order to bind and support the leuco dye and color developer on the support, various commonly used binders can be used as appropriate, such as polyvinyl alcohol, starch and its derivatives, methoxycellulose, hydroxyl, etc. Cellulose derivatives such as ethyl cellulose, carboxymethyl cellulose, methyl cellulose, and ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic amide/acrylic ester copolymer, acryl amide/acrylic ester/methacrylic acid ternary copolymer, styrene/ Maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt,
In addition to water-soluble polymers such as polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, Latex such as polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butadiene/acrylic copolymer, etc. can be used.

In addition, in the present invention, in addition to the leuco dye and color developer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, surfactants, thermofusible substances ( or lubricant), etc. can be used in combination. In this case, fillers include, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium and silica. , urea-formalin resin, styrene/methacrylic acid copolymer, polystyrene resin, and other organic fine powders. Examples of thermofusible substances include higher fatty acids or their esters, amides, or metal salts. In addition, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, dialkyl 3,4-epoxy-hexahydrophthalates, higher ketones, and other thermofusible organics. Examples include compounds having a melting point of about 50 to 200°C.

In the present invention, a protective layer containing a water-soluble polymer, a filler, and a conductive agent as main components is provided on the thermosensitive coloring layer having the above-described structure, thereby improving image stability and head matching properties. The generation of static electricity is reduced as much as possible. That is, the protective layer of the present invention functions as a protective layer that covers the head matching properties of these thermosensitive coloring layers and also increases the reliability of printed images against chemicals and the like.

The amount of protective layer constituents used is 3 for water-soluble polymers.
0-80% by weight, 10-50% for fillers
, and the conductive agent in an amount of 1.0 to 20% by weight, and the dry coating amount of the protective layer is 1.0 to 6.0 g/m''.Preferable results can be obtained when the amount of water-soluble polymer used is 1.0 to 20% by weight. If it is less than 30% by weight, resistance to chemicals etc. will be low,
If it is more than 80% by weight, sticking tends to occur. When the filler content is less than 10% by weight, sticking tends to occur, while when it is more than 50% by weight, the resistance to chemicals etc. becomes low. The amount of conductive agent used is such that the surface resistivity of the protective layer is 1.
It is set to be in the range of 0.012Ω or less, preferably 1010Ω or less. When the surface resistance is within this range,
Electrostatic charging of the heat-sensitive recording material during paper feeding is prevented, and troubles such as paper jams can be effectively eliminated. In order to provide such surface resistance, the conductive agent is usually contained in an amount of 1.0% by weight or more, although it varies depending on the type of the conductive agent. However, if the content of the conductive agent is too large, the moisture resistance and water resistance of the heat-sensitive recording material will deteriorate, so the content is usually 20% by weight or its upper limit.

Examples of water-soluble polymers used in the protective layer include polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, and acrylic acid amide. Acrylic ester copolymer, acrylic amide/acrylic ester/
Examples include methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein. these are,
Polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic ester,
It can also be used in combination with latexes such as vinyl chloride/vinyl acetate copolymers, polybutyl methacrylate, ethylene/vinyl acetate copolymers, and styrene/butadiene/acrylic copolymers.

Examples of fillers for the protective layer include calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium carbonate and silica. Other examples include organic fine powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin.

Examples of the conductive agent used together with the water-soluble polymer and filler described above include common salt, lithium chloride, sodium aluminate, sodium phosphate, calcium chloride, magnesium chloride, zinc chloride, zinc bromide, and zinc acetate.

In addition to electrolytes consisting of inorganic and organic salts such as potassium formate and sodium oxalate, polymeric anion salts such as polyacrylates, polymethacrylates, polystyrene sulfonates, styrene-maleic acid copolymer salts, and polyvinylbenzyl. Trimethylammonium chloride, poly(N-
methylvinylpyridium chloride), poly(N,H)
dimethyl-3,5-methylenepiperidium chloride,
Examples include polymer cation salts such as dimethyldiallylammonium chloride-sulfone copolymer.

By providing the above-mentioned protective layer, static electricity is prevented, and head matching properties and image stability are improved. On the other hand, there is no decrease in sensitivity that would otherwise accompany the provision of a protective layer. That's surprising.

The heat-sensitive recording material of the present invention can be prepared by a generally known method, for example, a leuco dye, a color developer at least separately, polyvinyl alcohol,
Together with an aqueous solution of water-soluble polymers such as hydroxyethyl cellulose, methyl cellulose, alkali salts of styrene-maleic anhydride copolymers, and starch, the dispersed particle size is 1 to 3 using a dispersing machine such as a ball mill, attritor, or sand mill.
After pulverization and dispersion until the particle size is μ, a filler, a thermofusible substance dispersion, an antifoaming agent, and the like are added to a certain formulation as necessary to prepare a heat-sensitive coloring layer coating solution. Furthermore, the protective layer coating solution is prepared by mixing or dispersing water-soluble polymers, fillers, conductive materials, and the like. Next, the heat-sensitive recording material of the present invention is prepared by sequentially coating and laminating these coating liquids on a support such as paper or synthetic paper.

〔effect〕

By providing a protective layer containing a water-soluble polymer, a filler, and a conductive agent, various troubles associated with electrostatic charging are prevented, a decrease in sensitivity is suppressed, and a heat-sensitive recording material with excellent image stability is produced. can get.

〔Example〕

The present invention will be explained in detail below using Examples and Comparative Examples.

Examples 1 and 2 Liquids (A) and (B) were prepared by pulverizing and dispersing mixtures having the following formulations using a ball mill and an attritor until the volume average diameter was approximately 1.5 μm.

[A) Liquid 3-(N-cyclohexyl-N-methyl)amino-6-
Methyl-7-anirite fluorane 20 parts by weight 10% polyvinyl alcohol aqueous solution 16〃Water 64〃 [B] Liquid benzyl p-oxybenzoate 10 parts by weight Calcium carbonate 1011 10% polyvinyl alcohol aqueous solution 16〃Water 54〃 Then (A) Liquid: [8] Liquid = 1: Both were mixed and stirred at a weight ratio of 4 to obtain a heat-sensitive coloring layer coating liquid.

Further, a mixture consisting of the following formulation was dispersed using a sand mill to obtain a protective layer coating solution.

Silica 5.0 weight - 10% polyvinyl alcohol aqueous solution 50.0 n Zinc stearate 5.0 parts by weight Conductive agent (material names are listed in Table 1) l, Q n Water 39
．． 0 # Next, these coating solutions were applied and dried on 50 g/m'' commercially available high-quality paper so that the dry adhesion amount was 3.0 g/m2 for the heat-sensitive coloring layer and 3.0 g/m2 for the protective layer. The heat-sensitive recording material of the present invention was prepared by laminating the above materials.

Comparative Example 1 A sample without the protective layer of the example was prepared in the same manner as the example.

Comparative Example 2 A film was prepared in the same manner as in the Example except that the conductive agent in the protective layer of the Example was removed (±).

Next, the heat-sensitive recording sheets of the above Examples and Comparative Examples were calendered using a super calender so that the glossiness (measured according to JIS-P8142) was 10 to 13%, and then G- Dynamic color development sensitivity and head matching tests were conducted using a 1rl FAX test machine. The test machine had an 8-dot 1 mm thermal head manufactured by Matsushita Electronic Components Co., Ltd., and a heating resistor of approximately 300 Ω/dot 1.
．． 850/mm, platen suppression 1.4kg, head voltage 13V, current conduction time 1.88m5ec and 2.19
Printed under two conditions of m5ec, and the image density was set to Macbeth RD5.
Measured with 1/1 (filter 1+1106). or,
Sticking was tested on solid ground before 2.19m5ec,
The head scum is 2.19m5ec and has a checkered pattern (black and white ratio 5
0%), 10 rivers were printed and the head was observed. Also, G-
The power-on time was 2.19m5e under the above conditions with the mFAX test machine.
In the sample printed in c, ethanol (95vol.
% JIS special grade) was impregnated into absorbent cotton and applied to the printed image area and non-image area, and the sample was observed. In addition, a sample printed under the same conditions as the ethanol test sample was placed on a wrap film (manufactured by Shin-Etsu Polymer Co., Ltd., trade name: Polymer Wrap) with the printed image side applied, and heated at 40°C for 1 hour under a load of 10 kg/cm. The sample was left to stand, and changes in the image area were confirmed.The surface resistance was also measured (measuring device: resistance meter manufactured by YHP Co., Ltd.).The above results are shown in Table 1.

Table-1 × ×-10-No practical problemX-〃 Yes ×-20-No color development in non-image area As can be seen from Table 1, the heat-sensitive recording material of the present invention has high dynamic color development sensitivity, is prevented from electrostatic charging, and has excellent head matching properties and chemical resistance, and is suitable for high-speed facsimile.

Patent applicant Rico Co., Ltd. Representative Patent Attorney: Toshiaki Ike, Ura

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive coloring layer containing a leuco dye and a color developer as main components is provided on a support, a water-soluble polymer, a filler, and a conductive agent are contained on the heat-sensitive coloring layer. 1. A heat-sensitive recording material characterized by being provided with a protective layer having a surface resistance of 10<12 >Ω or less.