JPH04286685A - Thermal recording material - Google Patents

Abstract

PURPOSE:To obtain a thermal recording material which is high in whiteness and excellent in shelf life of a color image by a method wherein a thermal coloring layer containing a dye precursor, a developer which reacts on the dye precursor to color, and a binding agent is provided, and the thermal coloring layer is made to contain an epoxy compound to be expressed by a specific chemical formula. CONSTITUTION:A sheet like base material and a thermal coloring layer which is formed on, at least, one surface of the sheet like base material and contains a coloring or light-colored dye precursor, a developer coloring the dye precursor by reacting thereon by heating, and a binding agent are provided. The thermal coloring layer is a thermal recording material containing an epoxy compound to be expressed by the chemical formula I. The thermal recording material is high in whiteness and excellent in shelf life of a color image and especially excellent in shelf life against oil and plasticizer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to heat-sensitive recording materials. More specifically, the present invention relates to a heat-sensitive recording material in which colored images have good storage stability against oils, plasticizers, and the like.

0002

[Prior Art] Many types of heat-sensitive recording materials have been developed that utilize a heated color-forming reaction between at least one colorless or light-colored dye precursor and a color developer made of phenols, organic acids, etc. A product has been published (Japanese Patent Publication No. 45-14039, etc.) and has been widely put into practical use. These heat-sensitive recording materials are used in a wide range of fields, including measurement recorders, computers and information communication terminals, facsimile machines, and automatic ticket vending machines.

These recording devices are equipped with a heating element such as a thermal head or a thermal pen, and by heating this element, it is possible to record a colored image. Recently, applications have become more diversified and equipment has become more sophisticated, and along with this, the quality required for thermal recording paper has also become more sophisticated. It has become possible to record in less than one minute, and there is a demand for heat-sensitive recording materials that can handle such high-speed recording.

[0004] Under these circumstances, as a method to improve the sensitivity of thermal recording paper, adding and using a sensitizer has been proposed. A thermosensitive recording material that satisfies the performance requirements in a well-balanced manner has not yet been obtained.

In heat-sensitive recording paper, a dye precursor and a phenol compound are each dispersed in the form of fine particles in the heat-sensitive recording layer, and when heated, one or both of them dissolves and come into close contact with each other, producing color. It is believed that.

As a phenol compound suitable for the above-mentioned heat-sensitive recording material, 2,2-bis(4'-hydroxyphenyl)propane (
Bisphenol A (melting point: 156° C.) is widely used (eg, US Pat. No. 3,539,375, Japanese Patent Publication No. 14039/1983). However, this bisphenol A has poor thermal responsiveness and has not necessarily been able to satisfy market demands for higher sensitivity of thermal recording paper as thermal recording apparatuses become faster or more compact.

[0007] Many sensitizers have been proposed to compensate for this drawback, such as waxes (Japanese Patent Laid-Open No. 48-198
No. 231), phthalate esters (
JP-A-57-116690, JP-A-58-982
85), benzyl phenyl ether derivatives (JP-A-59-155096), benzyl biphenyl (
JP-A No. 60-82382), naphthol derivatives (
JP-A No. 58-87094), carbonic acid diesters (
JP-A-58-136489) and the like have been proposed. However, when these are combined with the above-mentioned bisphenol A, a heat-sensitive recording material having sufficient quality in terms of whiteness, color development sensitivity, fog, etc. has not yet been obtained.

[0008] Japanese Unexamined Patent Publication No. 144193/1983 includes p.
- Benzyl hydroxybenzoate or methylbenzyl p-hydroxybenzoate has been proposed as a color developer to increase the sensitivity of heat-sensitive recording sheets; Because of this, there is a problem with its shelf life.

Furthermore, colored images formed on conventional heat-sensitive recording materials are unstable to plasticizers, oils, etc.
If a plastic film containing a large amount of plasticizer (for example, a soft polyvinyl chloride film) is attached to this colored image, or if it is stored with oil or fat attached,
There is a problem that the contact area becomes discolored.

[0010] Japanese Patent Application Laid-open No. 164579/1983 describes the following formula:

By adding a substance represented by [Chemical 5] (4,4'-diglycidyloxydiphenyl sulfone) to the heat-sensitive coloring layer,
It is described that a heat-sensitive recording material that forms a colored image with good storage stability is provided. However, although this material can control fading after color development, it tends to cause a change in color tone. As mentioned above, conventional heat-sensitive recording materials are
At present, they do not fully meet the high quality demands of the market, including color development characteristics and storage stability of colored images.

[0011]

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art, and provides a heat-sensitive recording material that has high whiteness and excellent preservability of colored images, especially against oils and plasticizers. The aim is to provide materials.

0012

[Means for Solving the Problems] As a result of intensive research conducted by the present inventors in order to solve the above-mentioned problems, the above-mentioned problems have been achieved by adding an aromatic epoxy compound having a specific chemical structure to the heat-sensitive coloring layer. This is a successful solution to the problem.

That is, 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 colorless or light-colored dye precursor formed on the sheet-like support. It has a thermosensitive coloring layer containing a color developer that reacts with the color developer to develop color, and a binder, and the thermosensitive coloring layer further has the following chemical formula (I):

It is characterized by containing an epoxy compound represented by the following formula.

In the heat-sensitive recording material of the present invention, the color developer has the following general formula (II):

embedded image [However, in formula (II), R1 to R9 are each
Each independently of the other, one member selected from a hydrogen atom, an alkyl group containing 1 to 5 carbon atoms, a -CH2 -CH=CH2 group (allyl group), and a benzyl group (-CH2 -C6H5) represented, X is -SO2 - group, or -
It is preferable that the compound contains at least one kind of compound represented by [representing an S-group].

In the heat-sensitive recording material of the present invention, the heat-sensitive coloring layer has the following general formula (III):

[Formula (III), R10 represents a benzene ring substituted with one member selected from a methyl group and a chlorine atom, and R11 represents a benzene ring substituted with one member selected from a methyl group and a carbonyl group. Expressed, R12 is

embedded image and n is 0 or an integer of 1 to 4].

[0016]

[Operation] The epoxy compound of formula (I) used in the present invention has excellent heat resistance and is sparingly soluble in water. The compound of this chemical formula (I) has the general formula (
It is preferably contained in the heat-sensitive coloring layer in an amount of 0.01 to 1% based on the weight of the compound II), thereby improving the storage stability of the colored image while maintaining the whiteness of the heat-sensitive coloring layer at a high level. can be significantly improved.

In the present invention, the compound of general formula (II) suitable as a color developer can be selected from, for example, the following compounds. Bis(4-hydroxyphenyl)sulfone, 4-hydroxyphenyl-4'-isopropoxyphenylsulfone, Bis(3-allyl-4-hydroxyphenyl)sulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone bis(3 -Methyl-4-hydroxyphenyl)sulfone 4,4'-thiobis(6-tert-butyl-3-methylphenol) 4,4'-thiobisphenol, 4,4'-thiobis(3-methylphenol), and 4,4'-thiobis(6-tert-butyl-3-methylphenol) -Hydroxyphenyl-4'-benzyloxyphenylthioether

The compound of the general formula (II) is effective as a color developer for dye precursors, and furthermore, while maintaining the white layer of the heat-sensitive coloring layer at a high level, the compound of the general formula (II) can be used together with the epoxy compound of the chemical formula (I). This is effective for improving the storage stability of colored images.

The color developer used in the present invention has the general formula (I
I), but not more than 1% of the total weight of the developer, such as 2,2-bis(4-hydroxyphenyl)propane (bisphenol A). , 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 1,4-bis[1
-Methyl-1-(4'-hydroxyphenyl)ethyl]
Benzene, 1,3-bis[1-methyl-1-(4'hydroxyphenyl)ethyl]benzene, dihydroxydiphenyl ether, benzyl p-hydroxybenzoate, bisphenol S, 4-hydroxy-4'-isopropyloxydiphenyl sulfone, 1 , 1-di(4-hydroxyphenyl)cyclohexane, 1,7-di(4-hydroxyphenylthio)-3,5-dioxaheptane, 3,
It may be used in combination with 3'-diallyl-4,4'-dihydroxyphenylsulfone.

In the present invention, the color developer is preferably used in an amount of 10 to 50% based on the total weight of the heat-sensitive coloring layer.

In the present invention, the thermosensitive coloring layer contains the general formula (
III) It is preferable to contain at least one dicarboxylic acid ester compound. The compound of general formula (III) is effective for improving the storage stability of colored images without reducing the whiteness of the heat-sensitive coloring layer. Examples of the dicarboxylic acid ester compound of general formula (III) include dibenzyl oxalate, di(p-chlorobenzyl) oxalate, di(p-methylbenzyl) oxalate,
and di(o-chlorobenzyl) adipate, etc. can be used. Generally, the dicarboxylic acid ester compound of general formula (III) has a content of 5 to 150% based on the total weight of the color developer.
% in the heat-sensitive coloring layer.

In the heat-sensitive recording material of the present invention, the dye precursor contained in the heat-sensitive coloring layer is one of conventional dye precursors for heat-sensitive recording materials, such as triphenylmethane-based, fluoran-based, and diphenylmethane-based compounds. One or more types selected from the leuco dyes used can be used. Examples of such dye precursors include 3-(4-diethyl-amino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindole-3-
yl)-4-azaphthalide, crystal violet lactone, 3-(N-ethyl-N-isopentylamino)
-6-Methyl-7-anilinofluorane, 3-diethylamino-6methyl-7-anilinofluorane, 3-diethylamino-6methyl-7-(o,p-dimethylanilino)fluorane, 3-(N -ethyl-p-toluidino)
-6-Methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diptylamino-6-methyl-7-anilinofluorane, 3-
(N-cyclohexine-N-methylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-7
-(o-chloroanilino)fluorane, 3-diethylamino-7-(m-trifluoromethylanilino)fluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6-methylfluorane, 3 -(N-ethyl-N-hexylamino)-6-methyl-7-(p-chloroanilino)fluoran, and 3
-cyclohexylamino-6-chlorofluorane, etc. can be used.

The thermosensitive color forming layer of the present invention contains a binder. This binder binds the components in the heat-sensitive coloring layer,
It is attached to a sheet-like support. As the binder, one selected from starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene, maleic anhydride copolymer salt, styrene, butadiene copolymer emulsion, etc. The amount of the above-mentioned coloring layer is 2 to 40% by weight, preferably 5 to 25% by weight, based on the total solid weight of the heat-sensitive coloring layer.

[0024] In addition to the above-mentioned components, various auxiliary materials may be added to the heat-sensitive coloring layer as required. For example, dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, other antifoaming agents, fluorescent dyes, color dyes, etc. can be added. The amount of these auxiliary agents added is preferably 5% or less, more preferably 0.5% or less based on the weight of the heat-sensitive coloring layer.
It is 1 to 3%.

In order to further whiten the heat-sensitive recording layer, inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, and fine particulate anhydrous silica may be added. Furthermore, stearic acid,
Waxes such as dispersions or emulsions of polyethylene, carnauba wax, paraffin wax, calcium stearate, zinc stearate, ester wax, etc. can also be added as necessary. The amount of these additives added is preferably 50% or less, more preferably 2 to 40%, based on the weight of the heat-sensitive coloring layer.

In the heat-sensitive recording material of the present invention, there are no particular limitations on the type, size, shape, etc. of the sheet-like support, and examples thereof include paper, synthetic fiber sheets, synthetic resin films, and composite sheets of two or more of these. Although paper can be selected from among others, paper is generally used.

To prepare the heat-sensitive recording material of the present invention, first, a coating solution for forming a heat-sensitive coloring layer is prepared. This coating liquid is prepared by dispersing predetermined components, particularly a dye precursor and a color developer using a grinder such as a sand mill, attritor, or sand grinder, and then blending these ingredients. Next, the coating liquid is applied to a sheet-like support to a predetermined weight or thickness using a coating means such as an air knife coater or a blade coater, and is solidified by drying or other means. Generally, the dry weight of the heat-sensitive coloring layer is 2 to 12 g/m2.
It is preferable that it is, and it is more preferable that it is 3-8 g/m2.

Further, the heat-sensitive recording material of the present invention may have an undercoat layer and/or an overcoat layer in order to improve its printability, water resistance, oil resistance, and other properties.

[0029]

EXAMPLES The present invention will be further explained with reference to the following examples. However, these are not intended to limit the scope of the invention. "Parts" and "%" in Examples and Comparative Examples represent "parts by weight" and "% by weight" unless otherwise specified.

A dispersion of components for a heat-sensitive coloring layer was prepared in the following manner. Preparation of Coating Solution for Thermosensitive Coloring Layer Solutions A to E were prepared by grinding each of the compositions having the following compositions using a sand grinder to an average particle size of 1.0 μm.

Liquid A (dye precursor dispersion)
minutes
Amount 3-(N-ethyl-N-isopentylamino) 20 parts
-6-methyl-7-anilinofluorane
10% polyvinyl alcohol solution
20 parts water

60 copies

Liquid B (dispersion containing developer and epoxy compound)
Growth
minutes
Amount 2,2-bis(4'-hydroxyphenyl)propane 10 parts Epoxy compound of formula (I)
5 copies (Trademark:
NTZ-95, manufactured by Nippon Soda Co., Ltd.) Calcium carbonate

15 parts (trademark: Gilliant-15, manufactured by Shiraishi Kogyo Co., Ltd.) 10% polyvinyl alcohol aqueous solution
20 parts water

50 copies

Liquid C (dispersion containing color developer and epoxy compound)
Ingredients
Amount 4-hydroxyphenyl-4'-isopropoxy 10 parts
Phenylsulfone (trademark: D-8, manufactured by Nippon Soda Co., Ltd.) Formula (I)
Epoxy compound (trademark: NTZ-95)
5 parts Calcium carbonate (Brilliant-15)
15 parts 10% polyvinyl alcohol aqueous solution
20 parts water

50 copies

Liquid D (dispersion containing developer, epoxy compound, and dicarboxylic acid ester)
Ingredients
Amount 4-hydroxyphenyl-4'-isopropoxy
10 parts Phenylsulfone (trademark: D
-8) Epoxy compound of formula (I) (trademark: NTZ-
95) 5 parts Dicarboxylic acid ester of formula (III)
10 copies (
Trademark: HS-3520, manufactured by Dainippon Ink Chemical Co., Ltd.)
Calcium carbonate (Brilliant-15)
5 parts 10% polyvinyl alcohol aqueous solution
20 parts water

50 copies

Liquid E (color developer-containing dispersion)
minutes
Amount 2,2-bis(4'-hydroxyphenyl)propane 10 parts Calcium carbonate
20 parts 10% polyvinyl alcohol aqueous solution
20 parts water

50 copies

Example 1 75 parts by weight of liquid A, 200 parts by weight of liquid B, 40 parts by weight of styrene-butadiene copolymer latex (solid content 50%),
25 parts by weight of zinc stearate emulsion (solid content 20%) was mixed to prepare a coating solution for a heat-sensitive coloring layer. This coating solution was coated and dried on a high-quality paper weighing 64 g/m2 to a dry coating weight of 5 g/m2 to form a heat-sensitive coloring layer, and then a protective layer having the following composition was applied on top of this coloring layer. The liquid was applied to give a dry weight of 3 g/m 2 and dried to form a protective layer to obtain thermosensitive recording paper. (Protective layer coating liquid)
minutes
Quantity Polyvinyl alcohol 10% aqueous solution
100 parts (polymerization degree 1100, saponification degree 98
．． 5%) Kaolinite clay (HG clay)
Part 6
Zinc stearate emulsion (20% liquid)
2 parts glyoxal (40% liquid)
Part 1

[0037] The above heat-sensitive recording paper was heated to a smoothness of 45 using a super calender.
Calendar treatment was performed so that the time was 0 seconds (measured according to Oken Beck (JIS-8123)). The following performance tests were conducted on this product. That is, the color development sensitivity was determined using a label printing machine D-805P manufactured by Koki Ishida Manufacturing Co., Ltd., with a head voltage of 22.2 V, a pulse width of 2.6 msec, and a period of 3.0 ms.
ec and an applied energy of 1.64 W/dot in a solid black step pattern in test mode, and the color density was measured using a Macbeth reflection densitometer (RD-514). Furthermore, using the printed matter obtained in the recording density test, the following (1)
) and (2) were conducted, and the residual rate of recorded image density was calculated using the following formula. (1) Oil resistance test: Printed matter was coated with salad oil and left at a predetermined temperature condition for a predetermined period of time. (2) Plasticizer resistance test: Layer polyvinyl chloride wrap film (manufactured by Nippon Carbide, trademark: HiSsoft) on the surface of the printed matter, sandwich it between glass plates from above and below, and apply a load of 60 g.
A weight was placed on the sample so that the temperature was 0.2 cm/cm2, and the sample was left for a predetermined time under the predetermined temperature conditions shown in Table 1. The test results are shown in Table 1.

Example 2 The same operation as in Example 1 was carried out. However, 75 parts by weight of liquid A,
Mix 200 parts by weight of liquid C, 40 parts by weight of styrene-butadiene copolymer latex (solid content 50%), and 25 parts by weight of zinc stearate emulsion (solid content 20%),
It was made into a heat-sensitive coloring coating liquid. Weighed 64g/m2 of this coloring coating liquid.
It was coated and dried on high-quality paper to a dry coating weight of 5 g/m2, and then a protective layer coating solution having the composition shown in Example 1 was applied on this coloring layer to a dry weight of 3 g/m2. The coating was applied and dried to obtain heat-sensitive recording paper. The test results are shown in Table 1.

Example 3 The same operation as in Example 1 was carried out. However, 75 parts by weight of liquid A,
Mix 200 parts by weight of Solution D, 40 parts by weight of styrene-butadiene copolymer latex (solid content 50%), and 25 parts by weight of zinc stearate emulsion (solid content 20%),
It was made into a heat-sensitive coloring coating liquid. Weighed 64g/m2 of this coloring coating liquid.
It was coated and dried on high-quality paper so that the dry coating weight was 5 g/m2, and then a protective layer coating liquid having the composition shown in Example 1 was applied on this coloring layer so that the dry weight was 3 g/m2. The coating was applied and dried to obtain heat-sensitive recording paper. The test results are shown in Table 1.

Comparative Example 1 The same operation as in Example 1 was carried out. However, 75 parts by weight of liquid A,
Mix 200 parts by weight of liquid E, 40 parts by weight of styrene-butadiene copolymer latex (solid content 50%), and 25 parts by weight of zinc stearate emulsion (solid content 20%),
It was made into a heat-sensitive coloring coating liquid. Weighed 64g/m2 of this coloring coating liquid.
It was coated and dried on high-quality paper so that the dry coating weight was 5 g/m2, and then a protective layer coating liquid having the composition shown in Example 1 was applied on this coloring layer so that the dry weight was 3 g/m2. The coating was applied and dried to obtain heat-sensitive recording paper. The test results are shown in Table 1.

[Table 1]

As is clear from Table 1, the heat-sensitive recording material (Example 1) containing the substance of formula (I) in the heat-sensitive coloring layer according to the present invention has a higher oil resistance of colored images than the comparative example. ,
It has excellent plasticizer properties and has excellent storage stability. Further, in the heat-sensitive recording material (Example 2) in which the color developer is composed of the compound of formula (II), the oil resistance and plasticizer resistance of the colored image are further improved. Furthermore, the formula (III) is contained in the heat-sensitive coloring layer.
The heat-sensitive recording material containing the compound (Example 3) has even better storage stability of its colored images.

[0042]

Effects of the Invention According to the present invention, it is possible to provide a heat-sensitive recording material that has good storage stability of colored images, particularly resistance to oils, plasticizers, and the like.

Claims (3)

[Claims] 1. A sheet-like support, a colorless or light-colored dye precursor formed on at least one surface of the sheet-like support, and a developer that reacts with the dye precursor under heating to develop color. It has a thermosensitive coloring layer containing a coloring agent and a binder, and the thermosensitive coloring layer further has the following chemical formula (I):
A heat-sensitive recording material characterized by containing an epoxy compound represented by the following formula: 2. The color developer has the following general formula (II):
[Chemical formula 2] [However, R1 to R9 in formula (II) each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a -CH2 -CH=CH2 group, and Represents one member selected from benzyl group, X is -SO2
The heat-sensitive recording material according to claim 1, comprising at least one compound represented by - group or -S- group. 3. The thermosensitive coloring layer further comprises the following general formula (III): [In formula (III), R10 is substituted with one member selected from a methyl group and a chlorine atom. represents a benzene ring, R11 represents a member selected from a methyl group and a carbonyl group, R12 represents a group, and n represents 0 or an integer from 1 to 4. The heat-sensitive recording material according to claim 1 or 2, containing at least one dicarboxylic acid ester compound.