JPH09202046A - Thermal recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the adhesion of refuse to a head and the abrasion of the head, in a thermal recording material wherein a thermal color forming layer containing a leuco dye and a coupler is provided on a support, by adding calcium carbonate and aluminum hydroxide to the thermal color forming layer respectively in an amt. equal to or more than that of the leuco dye. SOLUTION: In a thermal recording material wherein a thermal color forming layer containing a leuco dye and a coupler is provided on a support, calcium carbonate and aluminum hydroxide are respectively added to the thermal color forming layer in an amt. equal to or more than that of the leuco dye. That is, calcium carbonate and aluminum hydroxide are respectively added in a wt. ratio of 2-5 per the leuco dye 1. In this thermal recording material, a protective layer containing a water-soluble resin and pigment is provided on the thermal color forming layer and one containing the pigment of the protective layer and at least aluminum hydroxide is used. By this constitution, the thermal recording material reduced in the adhesion of refuse to a thermal head and abrasion and not generating background fog is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material using a leuco dye and a color developer, and more particularly to a heat-sensitive recording material for improving the adhesion of debris to a thermal head and the wear of the head, as well as the occurrence of background fog. .

[0002]

2. Description of the Related Art In recent years, a thermosensitive recording material having a thermosensitive coloring layer capable of coloring a recorded image on a support such as a paper, a synthetic paper, a plastic film or the like by causing a chemical or physical change by heat energy is simply Recording can be obtained only by heating and does not require complicated processing such as development and fixing.
It is widely used for various information devices such as printers, facsimiles, recorders, and measuring instruments, because it has the advantages of not generating noise during recording and being relatively easy and inexpensive to manufacture. .

Many of these heat-sensitive recording materials have been put to practical use, but among them, triphenylmethane-based, fluoran-based, and spiropyran-based colorless or pale leuco dyes and the leuco dyes A thermosensitive recording material containing an acidic substance that reacts to form a leuco body with color, for example, an organic acid or a phenolic acidic substance in the thermosensitive color forming layer as a color forming component, has a high coloring density of the obtained recorded image and is clear. , Is used as a particularly useful recording material.

However, such a heat-sensitive recording material has a problem that when printed by a thermal head such as a thermal line printer or a thermal serial printer, the print is faint due to the adhesion of residue on the thermal head and the image density is lowered. This is a phenomenon that occurs because the heat-melted material of the color former adheres to the thermal head as a residue, and the amount of heat conduction from the thermal head to the heat-sensitive recording material decreases as compared with the case where there is no residue.

To address this problem, it has been proposed to incorporate activated clay, calcined kaolins, silicates, aluminum oxides and the like into the thermosensitive coloring layer (Japanese Patent Publication No. 57-
No. 17438), the inclusion of these can surely reduce the adhesion of dross to the head, but as a side effect, the background fogging is likely to occur.

In order to achieve both the adhesion of the head residue and the reduction of the background fog, there is a proposal to include aragonite-based calcium carbonate in the heat-sensitive color developing layer (JP-A-59).
However, the problem of head wear is likely to occur this time. That is, although aragonite-based calcium carbonate is effective against adhesion of head scum and fog on the background, it causes wear of the head when printing is performed for a long time, and eventually causes a problem of missing print dots.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to obtain a heat-sensitive recording material in which adhesion of head debris and wear of the head are small, and in addition, the occurrence of background fog is small.

[0008]

According to the present invention, firstly, in a heat-sensitive recording material in which a heat-sensitive color developing layer containing a leuco dye and a color developer is provided on a support, carbon dioxide is contained in the heat-sensitive color developing layer. The present invention provides a heat-sensitive recording material containing calcium and aluminum hydroxide in the respective amounts of leuco dye or more.

Secondly, in the heat-sensitive recording material described in the first, there is provided a heat-sensitive recording material in which the leuco dye 1 contains the calcium carbonate and the aluminum hydroxide in a weight ratio of 2 to 5, respectively. is there.

Thirdly, the present invention provides a heat-sensitive recording material as described in the above first or second, wherein a protective layer containing a water-soluble resin and a pigment is provided on the heat-sensitive color forming layer.

Fourthly, the heat-sensitive recording material described in the above third is provided with at least aluminum hydroxide as a pigment of the protective layer.

The present invention will be described in detail below. As described above, the present invention contains calcium carbonate and aluminum hydroxide in the thermosensitive coloring layer, and the calcium carbonate and aluminum hydroxide in the thermosensitive coloring layer have a shape as particles and have oil absorbency. Since it is equipped, it is easy to absorb the component that becomes a residue of scum, that is, the hot melt of the color former,
It is thought that it is difficult to attach dust to the thermal head.

On the other hand, calcium carbonate has a function of making it difficult to cause background fog by being contained in the thermosensitive coloring layer, but has a property of easily abrading the thermal head itself. Further, it is known that aluminum hydroxide does not easily cause head wear, although it does not have a function of making the background fogging difficult.

According to the research conducted by the present inventors, the heat-sensitive color-forming layer contains calcium carbonate and aluminum hydroxide in an amount not less than the amount of the leuco dye. It was found that the head scum adhesion and head wear were reduced.
Furthermore, when a protective layer containing a water-soluble resin and a pigment as a main component is provided on such a thermosensitive coloring layer, head wear is further reduced, and when at least aluminum hydroxide is used as the pigment, head wear and It has been found that there is less head scumming.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The thermosensitive coloring layer in the present invention contains a leuco dye and a color developer as main components, and the leuco dye may be applied singly or in a mixture of two or more kinds. As the leuco dye, those applied to this type of heat-sensitive recording material are arbitrarily applied, and for example, leuco compounds that form dyes such as triallylmethane-based, fluorane-based, phenothiazine-based, auramine-based, and spiropyran-based are preferably used. To be Specific examples of such a mouth-coating base 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-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3 Screw (p
-Dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 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- (Np-tolyl-N-ethylamino) -6-methyl-7. -Anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2
-{N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6-
Bis (diethylamino) -9- (o-chloroanilino)
Xanthyl benzoate lactam}, 3-diethylamino-
6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 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) fluorane, benzoyl Leucomethylene blue,
6'-chloro-8'-methoxy-benzoindolino-pyrrirospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrrirospirane, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2-Methoxy-5'-chlorophenyl) phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3-
(2'-methoxy-5'-methylphenyl) phthalide,
3- (2'-methoxy-4'-diethylaminophenyl) -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) fluorane, 3- (N-ethyl-o-toluidino) -7- (α-
Phenylethylamino) fluorane 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-
Methyl-7- (α-phenylethylamino) fluoran, 3-diethylamino-7-piperidinofluoran,
2-chloro-3- (N-methyltoluidino) -7- (p
-N-butylanilino) fluorane, 3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7
-Α-naphthylamino-4'-bromofluorane, 3-
Diethylamino-6-methyl-7-mesitidino-4 ',
5'-benzofluorane etc.

As the color developer used in the present invention, various electron-accepting substances which react with the above leuco dye upon heating to develop a color are applied. Specific examples thereof are shown below. Examples thereof include phenolic substances, organic or inorganic acidic substances, and salts thereof.

Gallic acid, salicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid,
3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4′-isopropylidenediphenol, 1,1′-isopropylidenebis (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)
-Dimethylphenol), 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-
sec-butylidene diphenol, 4,4′-cyclohexylidene bisphenol, 4,4′-cyclohexylidene bis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α -Naphthol, β-naphthol, 3,5-xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolac type phenol resin, 2,2'-thiobis (4,6-dichlorophenol), catechol, resorcin , Hydroquinone, pyrogallol, phloroglysin,
Phloroglysin carboxylic acid, 4-tert-octylcatechol, 2,2'-methylenebis (4-chlorophenol), 2,2'-methylenebis (4-methyl-6-t)
ert-butylphenol), 2,2′-dihydroxydiphenyl, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, p-hydroxybenzoic acid-p-chloro. Benzyl, p-vidroxybenzoic acid-o-chlorobenzyl, p-hydroxybenzoic acid-p
-Methylbenzyl, p-hydroxybenzoic acid-n-octyl, benzoic acid, zinc salicylate, 1-hydroxy-2
-Naphthoic acid, 2-hydroxy-6 naphthoic acid, 2-
Zinc hydroxy-6-naphthoate, 4-hydroxy-
4'-chlorodiphenyl sulfone, bis (4-hydroxydiphenyl) sulfide, 2-hydroxy-p-toluic acid, 3,5-di-t-butylsalicylic acid, tartaric acid, acetic acid, maleic acid, citric acid, succinic acid, stearin acid,
4-hydroxyphthalic acid, boric acid, etc. are mentioned.

In the present invention, in addition to the leuco dye and the color developer, calcium carbonate and aluminum hydroxide are further contained in the thermosensitive coloring layer.

The content of calcium carbonate and the content of aluminum hydroxide are each more than the amount of the leuco dye used. Either calcium carbonate or aluminum hydroxide should not be less than the amount of leuco dye. It is important that each be added in excess of the amount of leuco dye. Optimally, the weight ratio of calcium carbonate and aluminum hydroxide to leuco dye 1 is 2 to 5, respectively.

As the calcium carbonate, both calcite type and aragonite type can be used. Further, aluminum hydroxide having an average particle diameter of 0.8 μm or 1.0 μm can be preferably used.

In the present invention, in order to bond and support the above-mentioned leuco dye, color developer and the like on a support, various conventional binders can be appropriately used. Further, in the present invention, auxiliary additives commonly used in this type of heat-sensitive recording material, such as a thermoplastic substance and a surfactant, may be used together with the leuco dye and the color developer, if necessary. . In this case, examples of the heat-fusible substance include higher fatty acids or esters, amides or metal salts thereof, various waxes, condensates of aromatic carboxylic acids and amines, phenyl benzoate esters, higher linear glycols. , 3,4-epoxy-dialkyl hexahydrophthalate, higher ketones, and other heat-fusible organic compounds having a melting point of about 50 to 200 ° C.

In order to produce the heat-sensitive recording material of the present invention,
When binding and supporting a leuco dye, a color developer, calcium carbonate, and aluminum hydroxide on a support, various conventional binders can be appropriately used. Specific examples thereof include the following. .

Polyvinyl coal, starch and derivatives thereof, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide /
Acrylic ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, etc. Others, polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride /
Examples thereof include emulsions such as vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, and latex such as styrene / butadiene copolymer and styrene / butadiene / acrylic acid copolymer.

The constitution of the protective layer in the present invention is mainly composed of a water-soluble resin and a pigment, and the water-soluble resin may be the same as the water-soluble polymer mentioned in the thermosensitive coloring layer. . Further, as the pigment, silica,
Calcium carbonate, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc,
Inorganic pigments such as kaolin, urea-formalin resins, styrene / methacrylic acid copolymers, organic pigments such as polystyrene resins and the like can be mentioned. According to the present inventors, by containing at least aluminum hydroxide, more head It has been found that dross adhesion and head wear can be improved.

The protective layer may further contain aluminum stearate, zinc stearate, calcium stearate, a lubricant such as various waxes, a surfactant, a water-proofing agent such as a polyamide resin, a melamine resin, and glyoxal, if necessary. Can be included. Further, it is also possible to provide an intermediate layer between the support and the thermosensitive coloring layer, and as the component of the intermediate layer, an organic or inorganic pigment, a binder resin,
It is selected from surfactants and the like as necessary.

[0026]

EXAMPLES The present invention will be specifically described with reference to examples. All parts and% shown below are based on weight.

Example 1 Fine hollow particle dispersion (copolymer resin mainly composed of styrene and acrylic resin, solid content concentration 27.5%, average particle diameter 1 μm, hollow ratio 50%) 48 parts styrene / butadiene co-polymer Polymerized latex (solid content concentration) 13 parts Water 39 parts A mixture consisting of the above-mentioned composition is stirred and dispersed to prepare an intermediate layer forming liquid, which is applied to a high-quality paper having a basis weight of 58 g / m ² and a dry weight of 5 g / An intermediate layer coated paper was obtained by coating and drying so as to obtain m ² .

<Heat-sensitive coloring layer coating liquid> (A liquid) 3- (N-cyclohexyl-N-methyl) amino-6-methyl-7-anilinofluorane 20 parts Hydroxyethyl cellulose 10% aqueous solution 20 parts Water 60 parts

(Liquid B) Bisphenol A 10 parts Calcium carbonate (calcite type) 10 parts Aluminum hydroxide (average particle size 0.8 μm) 10 parts Stearic acid amide 5 parts Completely saponified polyvinyl alcohol 10% aqueous solution 20 parts Water 60 parts The liquids A and B are dispersed in a sand mill so that the average particle diameter is 2 μm or less.

(C liquid) A liquid 10 parts B liquid 60 parts The above liquid C is mixed and stirred, and is coated and dried on the intermediate layer coated paper so as to have a weight of 4 g / m ² to form a thermosensitive coloring layer, Further, the layer surface was subjected to calendering so that the surface smoothness was 800 to 1000 seconds to obtain a heat-sensitive recording material.

[Example 2] In Example 1, 10 parts of calcium carbonate (calcite type) of the solution B was changed to 15 parts,
Furthermore, aluminum hydroxide having an average particle size of 0.8 μm 10
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 5 parts of aluminum hydroxide having an average particle size of 1.0 μm was used.

Example 3 In Example 1, the calcium carbonate (calcite type) of the liquid B was changed to 5 parts, and further,
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the amount of aluminum hydroxide (average particle size 0.8 μm) was changed to 15 parts.

Example 4 The following liquid D was mixed and stirred on the thermosensitive color developing layer of Example 1, dried and then coated and dried to a weight of 1.0 g / m ² , to form a protective layer. The surface of the layer was calendered to obtain a heat-sensitive recording material so that the surface smoothness was 800 to 1000 seconds.

(Solution D) 10% aqueous solution of completely saponified polyvinyl alcohol 50 parts Silica (average particle size 1.5 μm) 3 parts Zinc stearate 20% aqueous dispersion 25 parts Water 30 parts

[Example 5] A heat-sensitive material was prepared in the same manner as in Example 4 except that 3 parts of silica (average particle size: 1.5 µm) in the D liquid was replaced with 3 parts of calcium carbonate (calcite type). A recording material was obtained.

Example 6 As Example 4 except that 3 parts of silica (average particle size 1.5 μm) in the liquid D was changed to 3 parts of aluminum hydroxide (average particle size 0.8 μm). A heat sensitive recording material was obtained in the same manner.

Example 7 In Example 4, 3 parts of silica (average particle size 1.5 μm) in the D liquid was changed to 2 parts, and 2 parts of aluminum hydroxide (average particle size 1.0 μm) was newly added. A thermosensitive recording material was obtained in the same manner as in Example 4 except for the above.

[Comparative Example 1] In Example 1, 10 parts of calcium carbonate (calcite type) of the solution B was changed to 20 parts,
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that aluminum hydroxide was not added.

[Comparative Example 2] In Example 1, except that 10 parts of calcium carbonate (calcite type) in the solution B was changed to no addition,
2 parts of 10 parts aluminum hydroxide (average particle size 0.8 μm)
A heat-sensitive recording material was obtained in the same manner as in Example 1 except that the content was changed to 0 part.

[Comparative Example 3] In Example 1, 10 parts of calcium carbonate (calcite type) and 10 parts of aluminum hydroxide of solution B were changed to no addition, and silica (average particle size 1.5 μm) was used instead. A heat-sensitive recording material was obtained in the same manner as in Example 1 except that 10 parts were added.

<Evaluation> With respect to the thermal recording material obtained as described above, a head voltage of 0.4 W / dot, 1 line recording time of 10 msec / line, scanning line density of 8 using a thermal printing experimental apparatus having a thin film head. × 7.7 dots /
The pulse width was set to 0.8 msec under the condition of mm, and the printing test was conducted for each sample of 20 km.

The image density is measured by Macbeth densitometer RD-9.
I went to 14.

The amount of head wear was measured by using a stylus type three-dimensional surface roughness meter to measure how much the head was worn after the printing test and before the 20 Km printing test.
The maximum wear height (μm) is shown.

The adhesion of the head residue was expressed by the following criteria based on the result of observing the head surface with an optical microscope after a 20 Km printing test. ◯: Almost no adhesion of dross Δ: A small amount of adhesion of dross ×: Very large amount of adhesion of dross

As the evaluation of the background fog, 60 ° C.,
The background density when stored in an environment for 24 hours was measured with a Macbeth densitometer RD-914.

The results of each measurement are shown in Table 1.

[0047]

[Table 1]

It can be seen from Table 1 that when the heat-sensitive coloring layer contains calcium carbonate and aluminum hydroxide in an amount equal to or more than the amount of the leuco dye, the background fog is reduced, and the head scum adhesion and the head abrasion are reduced.

Further, by providing a protective layer containing a water-soluble resin and a pigment on such a thermosensitive coloring layer, head wear is further reduced, and further, when aluminum hydroxide is used as the pigment of the protective layer, It can be seen that the head wear and head scum adhesion are reduced.

[0050]

As described above, according to the constitutions of the present invention described in the above first and second aspects, by incorporating calcium carbonate and aluminum hydroxide in the thermosensitive coloring layer in an amount of at least the amount of each leuco dye, the background It is possible to obtain a heat-sensitive recording material with less fogging and less head debris adhesion and head wear.

Further, according to the configuration described in the third above,
By providing a protective layer containing a water-soluble resin and a pigment on the thermosensitive coloring layer having the configuration described in the first or second,
A heat-sensitive recording material with less head wear can be obtained.

Further, according to the fourth construction, the use of aluminum hydroxide as the pigment of the protective layer makes it possible to obtain a heat-sensitive recording material with less head abrasion and head scumming.

[Table 1]

Claims (4)

[Claims] 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer containing a leuco dye and a color developer, wherein each of the thermosensitive coloring layer contains calcium carbonate and aluminum hydroxide in an amount equal to or more than the amount of the leuco dye. A heat-sensitive recording material characterized in that 2. A heat-sensitive recording material comprising the leuco dye 1 containing the calcium carbonate and aluminum hydroxide in a weight ratio of 2 to 5, respectively. 3. The thermosensitive recording material according to claim 1, wherein a protective layer containing a water-soluble resin and a pigment is provided on the thermosensitive coloring layer. 4. The protective layer contains at least aluminum hydroxide as a pigment.
The heat-sensitive recording material as described.