JPH0444889A - heat sensitive recording material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a heat-sensitive recording medium that has high whiteness and is particularly excellent in storage stability of recorded images and imprintability.

``Prior art'' A thermosensitive recording material utilizes a coloring reaction between a colorless or light-colored basic dye and an organic or inorganic coloring agent to obtain a recorded image by bringing the two light-colored substances into contact with each other using heat. well known.

Such heat-sensitive recording media are relatively inexpensive, and because the recording device is compact and easy to maintain, they are used not only as recording media for facsimile machines and various computers, but also in a wide range of fields.

For example, one of the fields of use is word processing, POS
(Point of 5ales) With the expansion of systems, etc., the number of cases where they are used for office purposes and as POS labels is increasing.

However, when a POS system is introduced in a supermarket, etc., the thermal label paper used is water, plastic wrap, etc.
They often come in contact with oil, etc., and the recorded image (printed characters) on heat-sensitive labels has been observed to fade due to this influence.

Therefore, these label papers are required to have qualities such as water resistance, plasticizer resistance, and oil resistance.

Further, as word processing paper is often used in offices, it is required to have appropriate stampability, writing characteristics, etc.

By the way, in order to improve the storage stability of recorded images,
Attempts have been made to provide a protective layer on the heat-sensitive recording layer. However, at present, such protective layers usually contain inorganic pigments such as kaolin and calcium carbonate, or general organic pigments such as styrene.

However, since kaolin usually has plate-like crystals, the vermilion ink does not dry well, leaving problems with its suitability for printing.

Further, when calcilum carbonate is used, there is a disadvantage that the storage stability is significantly deteriorated, and furthermore, the above-mentioned organic pigments still have problems in both printability and storage stability.

``Problems to be Solved by the Invention'' An object of the present invention is to provide a heat-sensitive recording material that has high whiteness, excellent imprinting properties, and furthermore has excellent storage stability of recorded images, particularly excellent plasticizer resistance.

``Means for Solving the Problems'' The present inventors have developed a thermosensitive material using a coloring reaction between a colorless or light-colored basic dye and a coloring agent capable of forming a color upon contact with the dye on a support. It has been found that in a heat-sensitive recording material having a recording layer and a protective layer provided on the heat-sensitive recording layer, such problems can be extremely effectively achieved by incorporating an organic pigment having through-holes into the protective layer. The present invention has now been completed.

"Function" The organic pigment having through-holes used in the present invention has a special structure in that it is spherical in shape and each particle has a hole like a tunnel.

When such an organic pigment is contained in the protective layer of a heat-sensitive recording material, plasticizers, oils, etc. are very efficiently taken into the through-holes, resulting in extremely excellent storage stability and excellent imprintability. A heat-sensitive recording material with a high temperature and a high temperature can be obtained.

Incidentally, the above-mentioned ability was not observed in conventional completely spherical, aggregate, or oblate types of organic pigments, and it was found that the organic pigment of the present invention had very different characteristics.

The main component of the organic pigment used in the present invention is not particularly limited, but styrene-based polymers are preferred because they are industrially inexpensive and have a relatively high glass transition point.
For example, polymers such as styrene alone, styrene/acrylic, and styrene/methacrylic are preferred.

Furthermore, in order to impart heat resistance, intermolecular crosslinking is also possible.

The particle size of the organic pigment having through-holes of the present invention is 0.05 μm considering its use as a protective layer of a heat-sensitive recording material.
The range is preferably from m to 10 μm, and more preferably from 0.1 μm to 3 μm.
More preferably, it is about μm.

Examples of the binder contained in the protective layer include Eva, polyvinyl alcohol, hydroxyethylcellulose, methylcellulose, carpodium methylcellulose, starch and its derivatives, casein, sodium alginate, polyvinylpyrrolidone, sodium polyacrylate, polyacrylamide, and styrene/malein. Acid copolymer salt, styrene-butadiene emulsion, polyurethane resin, urea resin,
Examples include melamine resin.

Among such binders, partially saponified polyvinyl alcohol with a degree of saponification of 90% or less, when used in combination with the special organic pigment of the present invention, particularly improves the storage stability of recorded images and improves ink set during offset printing. Therefore, it has improved printability when used for POS labels, making it a particularly preferred binder.

The content of the organic pigment having through holes in the protective layer is not particularly limited, but it is preferably adjusted within the range of 5 to 500 parts by weight based on 100 parts by weight of the binder.

In addition, various pigments can be used in combination as long as the desired effects of the present invention are not impaired. Inorganic pigments such as silica, aluminum oxide, titanium oxide, urea formalin resin filler, polyethylene filler,
Examples include organic pigments having structures such as aggregates such as polystyrene fillers, flat bodies, and spherical bodies.

Furthermore, in the coating liquid that forms the protective layer, lubricants such as zinc stearate, calcium stearate polyethylene wax, carnauba wax, paraffin wax, and ester wax, and surfactants (dispersants, lubricants, etc.) such as sodium dioctyl sulfosuccinate, etc. Various auxiliary agents such as antifoaming agents) and antifoaming agents can also be added as appropriate. Further, in order to further improve water resistance, curing agents such as glyoxal, boric acid, dialdehyde starch, and epoxy compounds may be added.

The coating liquid thus prepared is applied onto the heat-sensitive recording layer using a suitable coating device, but the coating amount is 20 g/m2 in terms of dry weight.
If it exceeds 0.5 to 20 g/rrf, preferably 0.5 to 1.0 g/rrf, the recording sensitivity of the heat-sensitive recording medium may decrease significantly. It is desirable to adjust within a range of approximately Og/rd.

In the present invention, the basic dye contained in the heat-sensitive recording layer includes various known colorless or light-colored basic dyes,
Examples include the following compounds.

3.3-bis(p-dimethylaminophenyl)6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2- Dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3
-(2-methylindol-3-yl)phthalide, 3.
3-bis(1,2-dimethylindol-3-yl)5
-dimethylaminophthalide, 3.3-bis(1゜2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3.3-bis(9-ethylcarbazol-3-
yl)-6-dimethylaminophthalide, 3,3-bis(
2-phenylindol-3-yl)-6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-
Triallylmethane dyes such as (1-methylpyrrol-3-yl)-6-dimethylaminophthalide, 4,4'bis-dimethylaminobenzhydrylbenzyl ether, N
~Halophenyl-leucoauramine, N-2,4,5-
Diphenylmethane dyes such as trichlorophenyl leuco auramine, thiazine dyes such as benzoyl leucomethylene blue and p-nitrobenzoyl leucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spiro-dinaphthopyran , 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho(6'-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran, etc., rhodamine B-anilinolactam, rhodamine (p-nitroanilino) Lactam, rhodamine (0
-lactam dyes such as chloroanilino)lactam, 3-
Dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7
-Chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7
-Simethylfluorane, 3-(N-ethyl-p-toluidino)-7methylfluorane, 3-diethylamino-7
-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-diethylamino-7-dibenzyl 7minofluorane, 3-
Diethylamino-7-N-methyl-N-benzylaminofluorane, 3-diethylamino-7-N-chloroethyl-N-methylaminofluorane, 3-diethylamino-7-N-diethylaminofluorane, 3-(N-ethyl p-Toluidino)-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-p-toluidino)-6
-Methyl-7-(p-)luidino)fluorane, 3-diethylamine-6-methyl-7phenylaminofluorane, 3-dibutylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7- (2-carbomethoxy-phenylamino)fluorane, 3-(N-
cyclohexyl-N-methylamino)-6-methyltophenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-piperidino-
6-methyl-7-phenylaminofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane,
3-diethylami/-7-(o-chlorophenylamino)fluoran, 3-dibutylamino-7-(0-chlorophenylamino)fluoran, 3-pyrrolidino-6-methyl-7-P-butylphenylaminofluoran, 3-
(N-methyl-Nn-amyl)amino-6-methyl-
7-phenylaminofluorane, 3-(N-ethyl-N
-n-amyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-isoamyl)amino-6-methyl-7-phenylaminofluorane, 3
-(N-methyl-N-n-hexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-n-hexyl)amino-6-methyl-7-phenylaminofluorane , 3-(N-ethyl-N-β-ethylhexyl)amino-6-methyl-7-phenylaminofluorane, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl-7-phenylamino Fluoran dyes such as fluoran, 3-(N-ethyl-N-cyclopentyl)amino-6-methyl-7-phenylaminofluoran, etc. Of course, the dyes are not limited to these dyes, and two or more types of dyes can be used in combination.

Furthermore, various compounds are known as coloring agents used in combination with the above-mentioned basic dyes, for example, the following are exemplified.

4-tert-butylphenol, α-naphthol, β
-naphthol, 4-acetylphenol, 4-tert
-octylphenol, 4.4'-5ec-butylidenediphenol, 4-phenylphenol, 4.4'-dihydroxy-diphenylmethane, 4°4'-isopropylidenediphenol, hydroquinone, 4.4'-cyclohexylidenediphenol, 4.4'-(1,3-
dimethylbutylidene) bisphenol, 2,2-bis(
4-hydroxyphenyl)-4-methyl-pentane, 4
．． 4' dihydroxydiphenyl sulfide, 4.4'
-thiobis(6-tert-butyl-3-methylphenol), 4,4'-dihydroxydiphenylsulfone,
4-Hydroxy-41-methyldiphenylsulfone, 4
-Hydroxy-4'-methoxydiphenylsulfone, 4
-Hydroxy-41-isopropoxydiphenylsulfone, 4-hydroxy-3'4'-)limethylenediphenylsulfone, 4-hydroxy-3',4'-tetramethylenediphenylsulfone, 3,4-dihydroxy-4'-methyl Diphenylsulfone, bis(3-allyl-4-hydroxyphenyl)sulfone, 1,3 di(2
-(4-Hydroxyphenyl)-2-propyl]benzene, hydroquinone monobenzyl ether, bis(4-hydroxyphenyl) vinegar M7'' thyl ester, 4-hydroxybenzophenone, 2゜4-dihydroxybenzophenone, 2,4.4'- trihydroxybenzophenone,
2.2', 4゜4'-tetrahydroxybenzophenone, dimethyl 4-hydroxyphthalate, methyl 4-hydroxybenzoate, ethyl 4-hydroxybenzoate, propyl 4-hydroxybenzoate, 4-hydroxybenzoic acid-
5ec-butyl, pentyl 4-hydroxybenzoate, 4
-Hydroxybenzoic M-phenyl, benzyl 4-hydroxybenzoate, tolyl 4-hydroxybenzoate, chlorophenyl 4-hydroxybenzoate, phenylpropyl 4-hydroxybenzoate, phenethyl 4-hydroxybenzoate, P- 4-hydroxybenzoate Chlorobenzyl, 4
-Hydroxybenzoic acid - Phenolic compounds such as p-methoxybenzyl, novolac type phenolic resin, phenol polymer, benzoic acid, p-tertbutylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-sec-butyl-4-hydroxy Benzoic acid, 3-cyclohexyl-
4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, salicylic acid, 3-isopropylsalicylic acid, 3-tert-butylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-benzylsalicylic acid, 3 -(α-methylbenzyl)salicylic acid, 3-chloro-5-(α-methylbenzyl)su4Jthilic acid, 3-
Aromatic carboxylic acids such as phenyl-5-(α,α-dimethylbenzyl)salicylic acid, 3,5-diα-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids such as zinc, magnesium, aluminum, calcium. , organic acidic substances such as salts with polyvalent metals such as titanium, manganese, tin, and nickel. Of course, two or more of these coloring agents can be used in combination as necessary.

The ratio of the basic dye and coloring agent to be used is appropriately selected depending on the type of basic dye and coloring agent used, and is not particularly limited, but is generally based on 100 parts by weight of the basic dye. 100-700 parts by weight, preferably 150-4
About 0.00 parts by weight of coloring agent is used.

Preparation of coating liquids containing these generally uses water as a dispersion medium,
It is prepared by dispersing the dye and coloring agent together or separately using a stirring/pulverizing machine such as a ball mill, attritor, or sand mill.

Such coating liquids usually contain starches and binders as binders.
Hydroxyethylcellulose, methylcellulose, carboxymethylcellulose, gelatin, casein, gum arabic, polyvinyl alcohol, styrene/maleic anhydride copolymer salt, styrene/acrylic acid copolymer salt, styrene/butadiene copolymer emulsion, etc. have a total solid content. 2 to 40% by weight, preferably 5 to 25% by weight.

Furthermore, various auxiliary agents can be added to the coating liquid.
Examples include dispersants such as sodium dioctyl sulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl alcohol sulfate, fatty acid metal salts, other antifoaming agents, fluorescent dyes, and coloring dyes.

Additionally, inorganic pigments such as kaolin, clay, talc, calcium carbonate, calcined clay, titanium oxide, diatomaceous earth, fine particulate anhydrous silica, and activated clay may be added to the recording layer to improve the adhesion of debris to the recording head. You can also do it. In addition, to prevent sticking between the recording head and the recording head, a dispersion or emulsion of stearic acid, polyethylene, carnauba wax, paraffin wax, zinc stearate, calcium stearate, ester wax, etc. should be added to the recording layer. You can also do it.

Furthermore, in order to improve the recording sensitivity, for example, caproic acid amide, capric acid amide, valmitic acid amide,
Stearamide, oleic acid amide, erucic acid amide, linoleic acid amide, linoleic acid amide, N-methyl stearic acid amide, stearic acid anilide, N-methyl oleic acid amide, benzanilide, linoleic acid anilide, N-ethyl capric acid amide , N-butyllauric acid amide, N-octadecyl acetamide, N-oleicacetamide, N-oleylbenzamide, N-
Stearylcyclohexylamide, polyethylene glycol, 1-benzyloxynaphthalene, 2-benzyloxynaphthalene, 1-hydroxynaphthoic acid phenyl ester, 1,2-diphenoxyethane, 1,4-diphenoxybutane, 1,2-bis( 3-methylphenoxy)ethane, 1,2-bis(4-methoxyphenoxy)ethane, 1-phenoxy-2-(4-chlorophenoxy)ethane, 1-phenoxy-2-(4-methoxyphenoxy)
Ethane, 1-(2-methylphenoxy)-2-(4-methoxyphenoxy)ethane, dibenzyl terephthalate, dibenzyl oxalate, di(4-oxalate)
-methylbenzyl) ester, oxalic acid di(4-chlorobenzyl) ester, p-benzyloxybenzoic acid benzyl ester, p-benzylbiphenyl, 1°5-bis(P-methoxyphenoxy)-3-oxa-pentane,
1.4-bis(2-vinyloxyethoxy)benzene,
p-biphenyl-P-tolyl ether, benzyl-P-
Methylthiophenyl ether, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-
Various known thermofusible substances such as hydroxy-4-benzyloxybenzophenone can also be used as a sensitizer.

Among these sensitizers, 1,2-diphenoxyethane,
1.2-bis(3-methylphenoxy)ethane, 1-(
2-Methylphenoxy)-2-(4-methoxyphenoxy)ethane, oxalic acid dibenzyl ester, and oxalic acid di(4-methylbenzyl) ester not only have high whiteness and excellent image stability, but also have excellent recording density. However, since an excellent heat-sensitive recording material can be obtained, it is more preferably used.

The method of forming the recording layer is not particularly limited, and can be formed according to conventionally well-known and commonly used techniques. For example, to apply a coating liquid for a heat-sensitive recording layer onto a base paper, an appropriate coating device such as an air knife coater, a brush coater, a bar coater, a gravure coater, a curtain coater, a die coater, etc. is used. .

Further, the amount of the coating liquid to be applied is not particularly limited, and is generally adjusted within the range of 2 to 12 g7'rrf, preferably 3 to 10 g/rd in terms of dry weight.

Note that paper, plastic film, synthetic paper, etc. are used as the support.

In addition, various known techniques in the field of thermal recording material manufacturing are used, such as providing an undercoat layer on the support, providing a protective layer on the back side of the base paper, or applying an adhesive treatment to the back surface of the recording material and processing it into an adhesive label. can be added as necessary.

The heat-sensitive recording material thus obtained had high whiteness, excellent storage stability, and excellent imprintability because the protective layer contained a specific organic pigment.

"Example J" The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these examples.
"parts" and "%j" respectively indicate "parts by weight" and "% by weight" unless otherwise specified.

Example 1 ■ Preparation of liquid A 3-(N-ethyl-N-isoamyl)amino 6-methyl-7-phenylaminofluorane 10 parts Methyl cellulose 5% aqueous solution 5 parts water
40 parts of this composition was ground in a sand mill until the average particle size was 0.9 μm.

■ Preparation of Solution B 4-Hydroxy-4'-isopropoxydiphenylsulfone 30 parts Methylcellulose 5% aqueous solution 5 parts water
80 parts of this composition was ground in a sand mill until the average particle size was 3 μm.

■ CWl, preparation 1.2-di(3-methylphenoxy)ethane 20 parts methylcellulose 5% aqueous solution 5 parts water
55 parts of this composition was ground in a sand mill until the average particle size was 1 μm.

■ Formation of recording layer 55 parts of liquid A, 115 parts of liquid B, 80 parts of liquid C, 100 parts of polyvinyl alcohol (10 parts concentration), and 3 parts of calcium carbonate.
The coating liquid obtained by mixing and stirring 5 parts was coated on a base paper of 50 g/rrf so that the coating amount after drying was 6 g/rrT, and dried to form a recording layer. Next, the following protective layer coating solution was coated on the obtained recording layer so that the coated amount after drying was 5 g/rrr, and then dried and supercalendered to obtain a heat-sensitive recording paper having a protective layer.

■ Preparation of protective layer coating liquid Organic pigment with through holes (styrene/acrylic filler, particle size 0.5 μm, concentration 35%) 100 parts polyvinyl alcohol (PVA-117, manufactured by Kuraray Co., Ltd.)
Saponification degree 98.5%, concentration 10%) 300 parts zinc stearate aqueous emulsion (concentration 30%)
20 parts water
290 parts Example 2 In the composition of the protective layer coating solution of Example 1, the pigment composition was changed to 45 parts of organic pigment (concentration 35%) having through holes and 2 parts of kaolin.
A thermosensitive recording paper was obtained in the same manner as in Example I except that the amount was changed to 0 parts.

Example 3 The same procedure as in Example 1 was carried out, except that the composition of the protective layer coating solution in Example 1 was changed to 45 parts of an organic pigment having through holes (concentration 35%) and 20 parts of aluminum hydroxide. A thermosensitive recording paper was obtained.

Example 4 In the composition of the protective layer coating liquid of Example 1, polyvinyl alcohol was replaced with PVA-217 (manufactured by Kuraray Co., Ltd., concentration 10%), which is partially saponified polyvinyl alcohol with a degree of saponification of 88%.
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that .

Example 5 In the composition of the protective layer coating liquid of Example 2, polyvinyl alcohol was replaced with PVA-217, which is a partially saponified polyvinyl alcohol with a degree of saponification of 88% (manufactured by Kuraray Co., Ltd., 1° 1O% concentration).
A thermosensitive recording paper was obtained in the same manner as in Example 2 except that .

Comparative Example 1 In the composition of the protective layer coating solution of Example 1, 3 parts of kaolin was used instead of 100 parts of the organic pigment (concentration 35%) having through holes.
A thermosensitive recording paper was obtained in the same manner as in Example 1 except that 5 parts were used.

Comparative Example 2 Heat-sensitive coating was carried out in the same manner as in Example 1, except that in the composition of the protective layer coating liquid in Example 1, 35 parts of rhusium carbonate was used instead of 100 parts of the organic pigment (concentration 35%) having through-holes. I got the recording paper.

Comparative Example 3 In the composition of the protective layer coating solution of Example 1, 100 parts of the organic pigment with through holes (concentration: 35%) was replaced by a completely spherical organic pigment (styrene/acrylic filler 2 concentration: 35%).
) A thermosensitive recording paper was obtained in the same manner as in Example 1, except that Thermosensitive recording paper was used.

The following evaluation tests were conducted on the eight types of heat-sensitive recording bodies thus obtained, and the results are listed in Table 1.

[Whiteness]

The whiteness of the recording layer was measured using a Hunter whiteness meter.

[Color density] Thermal printer (manufactured by Texas Instruments, PC
The color density of the recorded image obtained by printing with a Macbeth densitometer (manufactured by Macbeth Co., Ltd.) was measured using a Macbeth densitometer (Macbeth Co., Ltd.).

RD-100R model).

[Plasticizer resistance]

A vinyl chloride wrap film (manufactured by Mitsui Toatsu Chemicals ■) is wrapped three times around a polypropylene pipe (40+wφ pipe), and a heat-sensitive recording material with colored print is sandwiched on top of it so that the colored side of the print is facing outward. A vinyl chloride wrap film was wrapped three times on top, and the plasticizer resistance was evaluated from the print density after being left at 40°C for 8 hours. The evaluation criteria for plasticizer resistance were as follows.

◎: Very good recording density with almost no decrease.

○: The recording density is slightly decreased, but there is no practical problem.

×: Significant decrease in recording density, impractical.

[Imprintability]

A stamp made of shachihata vermilion was stamped on the blank part of the recording paper, and after 1 minute, the stamped part was wiped with gauze to perform a fixation test. The evaluation criteria for sealability were as follows.

O: Very good fixing.

×: Poor fixation, practically impossible.

Table 1 - "Results" The heat-sensitive recording material obtained in the present invention had high whiteness and was particularly excellent in plasticizer resistance and imprintability.

Claims (2)

[Claims] (1) A heat-sensitive recording layer on a support that utilizes a color reaction between a colorless or light-colored basic dye and a coloring agent that can develop color when it comes into contact with the dye, and a protective layer on the heat-sensitive recording layer. 1. A heat-sensitive recording material comprising a protective layer containing an organic pigment having through-holes. (2) The heat-sensitive recording material according to claim (1), wherein the protective layer contains partially saponified polyvinyl alcohol having a degree of saponification of 90% or less.