JPH0410976A - Thermal recording material - Google Patents

Abstract

PURPOSE:To enhance the erasure preventing effect of a recording image with the elapse of time by adding 2-anilino-3-methyl-6-dibutylaminofluorane, a compound having an ether bond in its structural formula, and a specific wax composition to the thermal color forming layer provided on a support. CONSTITUTION:A thermal color forming layer containing an electron donating leuco dye and an electron acceptive compound is provided on a support and 2-anilino-3-methyl-6-dibutylaminofluorane, a compound having at least two ether bonds in its structural formula and a paraffin wax composition wherein the melting start temp. of an endothermic peak obtained by differential heat analysis is 60 deg.C or higher are added to the thermal color forming layer. As the compound having the ether bond, 1-(4-methoxyphenyl)-2-phenoxypropane, di(4,4'- methoxyphenoxyethyl)ether and 1,2-di(phenoxyethoxy)benzene are pref. As the paraffin wax composition, 'Cut Wax' wherein a low m.p. component is removed is used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a heat-sensitive recording material, and in particular to a heat-sensitive recording paper that prevents recorded images from fading over time and improves the adhesion of residue to a thermal head, etc. be.

(Prior Art) Recording materials using electron-donating colorless dyes and electron-accepting compounds are already well known as pressure-sensitive paper, thermal paper, light-sensitive pressure-sensitive paper, electrically conductive thermal recording paper, thermal transfer paper, and the like. For example, British Patent No. 2140449, U.S. Patent No. 4480052, U.S. Pat.
For details, see No. 60-123557. In particular, heat-sensitive recording materials include Tokoku No. 43-4160 and No. 45-1403.
I am familiar with No. 9 etc.

In general, when heat-sensitive recording materials are used as recording sheets, they have the advantage that recording devices can be made lighter and smaller, and their use has rapidly come into use in recent years.

However, heat-sensitive recording materials using an electron-donating colorless dye and an electron-accepting compound have the disadvantage that the recorded image loses color when stored for a long period of time. This decolorization is particularly accelerated by the effects of heat and humidity, and under such conditions the commercial value is significantly reduced.

Various proposals have already been made to improve these drawbacks. For example, in Special Publication No. 51-43386, 2.2
Adding a phenol derivative such as °-methylenebis(4-methyl-5-te, rt-butylphenol); JP-A-53-17347 describes adding a water-insoluble phenol resin such as rosin-modified resin; Showa 56-7
No. 2996 describes the addition of a terephthalate ester such as diethyl terephthalate.

However, all of these methods have the disadvantage that not only the effect of preventing color fading is insufficient, but also unnecessary color development (fogging) occurs during the production or storage of the recording material.

In addition, thermal recording materials utilize the process of heating and melting an electron-donating colorless dye and an electron-accepting compound to develop color.While recording was performed using a T1 thermal head, etc.
The scum of the melt may adhere to the surface of the thermal head, etc., and this scum may be transferred to the heat-sensitive recording material, staining the recording surface, or the scum may prevent the heat-sensitive recording material from coming into close contact with the thermal head, etc., resulting in inaccurate recording. It also had drawbacks such as the inability to do so.

(Object of the invention) The first aspect of the invention. An object of the present invention is to provide thermal paper that prevents recorded images from fading over time.

The second object is to provide thermal paper that exhibits less fog during manufacturing and storage. The third object is to provide a heat-sensitive recording material with improved adhesion of residue to a thermal head and the like. Finally, for all purposes 1 to 3, the high-speed printing characteristics (high sensitivity) that have been traditionally required of thermal paper
The aim is to realize this without compromising the

(Structure of the Invention) As a result of intensive studies, the present inventor has found that a heat-sensitive recording material comprising a heat-sensitive coloring layer containing an electron-donating colorless dye and an electron-accepting compound as main components is provided on a support. Contains 2-anilino-3-methyl-6-dibutylaminofluorane in the layer and a compound having at least two ether bonds in the structural formula, and further melts the endothermic peak obtained by differential thermal analysis. Starting temperature is 60℃
It has been found that by containing the wax composition described above, the effect of preventing discoloration of recorded images over time is significantly improved. This effect is independently expressed without deteriorating other performances such as "fogging".

Examples of compounds having at least two ether bonds in the structural formula include 1,2-diphenoxyethane, 1-phenoxy-2-(2-methylphenoxy)ethane, 1-
Phenoxy-2-(4-ethylphenoxy)ethane, 1
-phenoxy-2-(4-tertbutylphenoxy)
Ethane, 1-phenoxy-2-α-naphthoxyethane,
1-phenoxy-2-β-naphthoxyethane, 1.2-
Di(2,2°-ratylphenoxy)ethane, 1-(2-
methylphenoxy)-2-(2'-methoxyphenoxy>ethane, 1,2-di(2,2'methylphenoxy>ethane, l-<4-ethylphenoxy)-2-(2°-chlorophenoxy)ethane, 1 -(3-methylphenoxy)-2-(4'-methoxyphenoxy)ethane, 1.4
-diphenoxy-n-butane, 1-(4-methoxyphenoxy)-2-(4°-methoxyphenoxy)propane1. l-F, enoxy-2-(α-naphthoxy)propane, 1-phenoxy-2-(β-naphthoxy)propane, 1,3-di(4,4°-methoxyphenoxy)propane, di(4,4”) -methoxyphenoxyethyl) ether, di(4,4'-ethoxyphenoxyethyl)ether, 12-di(phenoxyethoxy)benzene, di(4
゜4°-methoxyphenoxyethoxy)methane, 1(4
-methoxyphenoxy)-2-phenoxypropane, 1
-phenoxy-2-(4-methquinphenoxy)propane and the like. Among these, 1-(4-methoxyphenoxy)-2-phenoxypropane (melting point 87
C), di(4°4°-methoxyphenoxyethyl)ether (melting point 100°C), and 1,2-di(phenoxyethoxy)benzene (melting point 120°C) are preferred.

It is difficult to obtain a paraffin wax composition whose endothermic peak melting start temperature obtained by differential thermal analysis is 60 ° C. or higher by normal methods, and it is generally prepared by fractional distillation etc. So-called "cut wax" is a product that removes low melting point components from among multiple components.
need to be used. In order to fully exhibit the performance of the present invention, it is necessary to remove components having a melting start temperature of less than 60°C.

The differential thermal analysis referred to in the present invention was performed using a PerkinElmer Model DSC-7. For analysis, 5 mg of wax solid was heated from 40°C to 130°C at a heating rate of 40°C/min under a nitrogen stream, and the obtained DS
This was determined by reading the melting start temperature from the endothermic peak of the C curve.

As a result of further investigation, the present inventors found that, although the reason is not clear, the heat-sensitive recording material using the paraffin wax in the heat-sensitive coloring layer had a lower amount of residue adhering to the inothermal head than before when printing. They found that the amount of heat-sensitive recording materials was significantly lower than that of other heat-sensitive recording materials, and arrived at the final invention.

The paraffin wax used in the present invention is used in an amount of 5 to 200, preferably 20 to 150% by weight of the electron-donating colorless dye contained in the heat-sensitive coloring layer. If it is less than 5% by weight, the performance of the present invention cannot be fully expressed, which is not preferable. Moreover, even if it exceeds 200% by weight, no further effect can be obtained, which is not preferable.

In the electron-donating colorless dye according to the present invention, it is necessary that 2-anilitu-3-methyl-6-dibutylaminofluorane accounts for 50% by weight or more of the entire electron-donating colorless dye. Under the above-mentioned conditions, it is also possible to use it in combination with other electron-donating colorless dyes. Examples of electron-donating colorless dyes that can be used in combination include triphenylmethane tuclide compounds, fluoran compounds, phenothiazine compounds,
There are various compounds such as indolylphthalide compounds, leucoolamine compounds, rhodamine lactam compounds, triphenylmethane compounds, triazene compounds, spiropyran compounds, and fluorene compounds. Specific examples of phthalide microscopy are provided in U.S. Patent Reissue No. 23024,
U.S. Patent No. 3491111, U.S. Patent No. 349111
'2 No. 3491116 and No. 350917
No. 4, specific examples of fluorans are given in U.S. Patent No. 362
No. 4107, No. 3627787, No. 364101
No. 1, No. 3462828, No. 3681390,
3920510, 3959571, specific examples of spiropyrans are U.S. Pat. No. 3971808, pyridine and pyrazine compounds are U.S. Pat.
No. 246318, specific examples of fluorene compounds are described in Japanese Patent Application No. 61-240989, etc.

Among these, 2-awaramino-3-H, halo, alkyl, or alkoxy-6-substituted aminofluorane, which develops a black color, is particularly effective.

The electron-accepting compound according to the present invention is a phenol derivative,
Metal salts of aromatic carboxylic acids, acid clay, bentonite,
Novolac resin, gold 1*lW novolac resin, metal complex, etc. are used. Examples of these are
No. 9, Special Publication No. 45-14039, Japanese Patent Publication No. 140-1973
No. 483, JP-A-48-51510, JP-A-57-2
No. 10886, Japanese Unexamined Patent Publication No. 1983. No.-87089, JP-A-5
9-11286, JP-A-60-176795, JP-A-61-95988, etc.

Examples of these 7 parts include 2,2'-bis(4-hydroxyphenyl)propane, 4-phenylphenol, 11-bis(3-chloro-4-hydroxyphenyl)cyclohexane, 1 .1
-bis(4-hydroxyphenyl)cyclohexane, 1
．． 1-bis(3-chloro-4-hydroxyphenyl)-
2-ethylbutane, 4.4"5ec-octylidene diphenol, 4.4° -5ec-butylidene diphenol, 4-p-methylphenylphenol, 4.4°
-Methylcyclohexylidenephenol, 4.4-isopentylidenephenol, bis(3-aryl-4-hydroxyphenyl)sulfone, 4-hydroxyphenyl-3° 4゛dimethylphenylsulfone, 4- (4-
Examples include isopropoxyphenylsulfonyl)phenol, bis[2-(4-hydroxyphenylthio)ethoxycomethane, and benzyl p-hydroxybenzoate.

Examples of salicylic acid derivatives include 4-pentadecylsalicylic acid, 3.5-di(α-methylbenzyl)salicylic acid, 3.
．． 5-di(ter-octyl)salicylic acid, 5-α-(
p-α-methylbenzylphenyl) ethylsalicyl [
2,3-α-methylbenzyl-5-ter-octylsalicylic acid, 5-tetradecylsalicylic acid, 4-hexyloxysalicylic acid, 4-cyclohexyloxysalicylic acid, 4-decyloxysalicylic acid, 4-dodecyloxysalicylic acid, 4-penta Decyloxysalicylic acid, 4-
Octadecyloxysalicylic acid, etc., and zinc,
There is aluminum, calcium, copper, and salt. Among these, bisphenol These electron-accepting compounds are electron-donating colorless dyes.
It is preferable to use 800% by weight, particularly preferably 100 to 500% by weight.

If it is less than 50% by weight, the color development will not be sufficient, and if it is added more than 800% by weight, no further effect can be expected, which is not preferable.

Next, a typical method for producing a heat-sensitive color forming layer of the present invention will be described.

The electron-donating colorless dye, the electron-accepting compound, and the compound having at least two ether bonds in its structural formula are dispersed to a size of several microns or less using a ball mill, sand mill, etc., together with an aqueous solution of a water-soluble polymer such as polyvinyl alcohol. The ether compound related to the present invention may be added to either or both of a color former and a color developer and dispersed simultaneously, or in some cases, a eutectic may be prepared in advance and dispersed.

These dispersions are mixed after dispersion, and pigments and
Surfactant, binder, gold. @ Soap, paraffin wax specified by the present invention, antioxidant, ultraviolet absorber, etc. are added to make a heat-sensitive coating liquid.

The obtained heat-sensitive coating liquid is coated and dried on high-quality paper, high-quality paper with an undercoat layer, synthetic paper, plastic film, etc., and then smoothed by calendering to become the desired heat-sensitive 8-coating material. .

The binder used in the present invention is preferably a compound that dissolves at least 5% by weight in water at 25°C. (containing polyvinyl alcohol), methi-sha cellulose, carboxymethyl cellulose, starches (including modified starch), gelatin, gum arabic, casein, styrene-maleic anhydride copolymer hydrolyzate, polyacrylamide, vinyl acetate-polyacrylic Examples include saponified acid copolymers. These binders are used not only for dispersion but also for the purpose of improving coating film strength. For this purpose, styrene-butadiene copolymers, vinyl acetate copolymers, acrylonitrile-butadiene copolymers, A synthetic polymer latex binder such as methyl acrylate/butadiene copolymer or polyvinylidene chloride may also be used. Further, an appropriate crosslinking agent may be added depending on the type of these binders as necessary.

As the pigment, calcium carbonate, barium sulfate, lithopone, waxite, kaolin, silica, amorphous silica, etc. are used.

As the metal soap, higher fatty acid metal salts are used, such as zinc stearate, calcium stearate, aluminum stearate, and the like.

Furthermore, surfactants, antistatic agents, ultraviolet absorbers, antioxidants, antifoaming agents, conductive agents, fluorescent dyes, coloring dyes, and the like may be added as necessary.

The coated heat-sensitive recording material is dried-smoked and subjected to a treatment such as a calender before being used.

Further, a protective layer may be provided on the heat-sensitive recording layer, if necessary. As the protective layer, any material known as a protective layer for sensitive ridges and self-recording materials can be used.

Furthermore, if necessary, a back coat layer may be provided on the opposite side of the support of the heat-sensitive recording material from the heat-sensitive recording layer. As the backcoat layer, any material known as a backcoat layer for heat-sensitive recording materials can be used.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited only to the Examples below.

(Example-1) 2-anilino-3-methyl-6-di-N-butylaminofluorane as an electron-donating colorless dye, bisphenol A as an electron-accepting compound, 1 as an ether compound
-(4-Methoxyphenoxy)-2-phenoxy-propane, 20 g of each was dispersed with 100 g of 5% polyvinyl alcohol (Kuraray PVA-105) aqueous solution in a ball mill overnight to make the average particle size 1.5 μm or less, and each dispersion was I got the liquid.

In addition, 80 g of calcium carbonate was dispersed with 160 g of 0.5% sodium hexametaphosphate solution using a homogenizer,
A pigment dispersion was obtained.

Each of the dispersions prepared as described above was mixed with 5 g of the electron-donating colorless dye dispersion, 10 g of the electron-accepting compound dispersion, and 1-(
10 g of 4-methquinphenoxy)-2-phenoxy-propane dispersion and 15 g of calcium carbonate dispersion were mixed, and further 3 g of 21% zinc stearate emulsion was added.
A heat-sensitive coating liquid was obtained by adding 2 g of a paraffin wax dispersion (Hidrin E-139 manufactured by Middle East Oil Co., Ltd.) whose endothermic peak melting start temperature was 63.5° C. according to differential thermal analysis of the solid material. This heat-sensitive coloring layer coating solution was coated on high-quality paper using a coating bar until the dry weight of the coating layer was 5 g/
m' and dried at 50° C. for 1 minute to obtain a heat-sensitive recording material.

(Example-2) The paraffin wax dispersion of Example-1 (Middle East Oil Company H
A heat-sensitive coating liquid was prepared using a paraffin wax dispersion (Hidrin F-516) manufactured by Middle East Oil Co., Ltd. instead of Hidrin E-139), and a heat-sensitive recording material was obtained. F-516
The melting start temperature of the endothermic peak obtained by differential thermal analysis of the solid material was 62.0°C.

(Example-3) A heat-sensitive coating liquid was prepared using di(44-methoxyphenoxyethyl) ether instead of 1-(4-methoxyphenoxy)-2-phenoxy-propane in Example-1, and a heat-sensitive recording material was prepared. Obtained.

(Example-4) A heat-sensitive coating liquid was prepared using 1,2-di(phenoxyethoxy)benzene instead of 1-(4-methoxyphenoxy)=2-phenoxy-propane in Example-1, and a heat-sensitive recording material was prepared. I got it.

(Comparative example-1) Paraffin wax dispersion of Example-1 (H
A heat-sensitive coating liquid was prepared using a paraffin wax dispersion (Hidrin P-7) manufactured by Middle East Oil Co., Ltd. instead of Hidrin E-139) to obtain a heat-sensitive recording material. The endothermic peak melting start temperature obtained by differential thermal analysis of the solid P-7 was 43.4°C.

(Comparative Example-2) Paraffin wax dispersion of Example-1 (H
idrin E-139>, a paraffin wax dispersion (HidriTI D-337) manufactured by Middle East Oil Co., Ltd.
) to prepare a heat-sensitive coating liquid and obtain a heat-sensitive recording material. D-
The melting start temperature of the endothermic peak obtained by differential thermal analysis of the solid substance of No. 337 was 46.4°C.

(Comparative Example-3) A heat-sensitive coating liquid was prepared using 2-anilino-3-methyl-6-dinithylaminofluoran instead of 2-anilino-3-methyl-6-dibutylaminofluoran in Example-1. A thermosensitive recording material was obtained.

<Comparative Example-4) β-naphthylbenzyl ether (
A heat-sensitive coating liquid was prepared using a heat-sensitive coating solution (melting point: 101°C) to obtain a heat-sensitive recording material.

(Comparative Example-5) A heat-sensitive recording material was obtained by sub-plating the heat-sensitive coating liquid without using the 1-(methoxyphenoxy)-2-phenoxypropane of Example-1.

The heat-sensitive recording material obtained as described above was surface-treated with a calender, and the thermal head manufactured by Kyocera ■ (KLT-
2'l 6-8MPD1) and 100k just before the head
g/c++! The head voltage was 24V, the pulse cycle was 1Qmsec, and
While using the pressure roll under the following conditions, the pulse width is 1. 0
Printing was performed using m5ec, and the print density was measured using a Macbeth reflection densitometer RD-918.

Furthermore, the heat-sensitive recording material printed under the above printing conditions was left in a constant temperature bath at a temperature of 60°C and a humidity of 30%, - a dry oven at a temperature of 70°C, and after 24 hours, the printed image and the density of the non-printed area were again examined. was measured. The residual rate (%) of the image was determined by dividing the print density after 24 hours by the print density immediately after printing.

Further, 30 copies of CCITT No. 8 charts were made from the obtained heat-sensitive recording material using a facsimile UF-32 manufactured by Matsushita Electric Transmission Co., Ltd., and the state of the thermal head and the state of copying were observed. (◯ - The hemlock is not stained. △ - The hemlock is stained black, but there are no scratches on the printed area - 1° x - Scratches occur on the printed area.) The results are shown in Table 1.

As shown in Table 1, it can be seen that the heat-sensitive recording material according to the present invention exhibits significantly less discoloration of recorded images over time, less fogging on the background, and improved head residue adhesion. .

Table-1

Claims (2)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive coloring layer containing an electron-donating colorless dye and an electron-accepting compound is provided on a support, the heat-sensitive coloring layer contains 2-anilino-3-methyl-6
- A paraffin wax composition containing dibutylaminofluorane and a compound having at least two ether bonds in its structural formula, and further having a melting start temperature of an endothermic peak obtained by differential thermal analysis of 60°C or higher. A heat-sensitive recording material characterized by containing a substance. (2) The paraffin wax composition has a melting start temperature of 60% among the multiple components constituting the paraffin wax.
The heat-sensitive recording material according to claim (1), which is a paraffin wax composition obtained by removing components with a low melting point below °C.