JPS63299976A - Thermal recording material - Google Patents

Abstract

PURPOSE:To make it possible to record a high-density clear image even with a minute quantity of thermal energy, by using as a base a synthetic paper having a density in a specified range. CONSTITUTION:A synthetic paper having a density of not more than 0.90 g/cm<2> is used as a base on which a thermal color forming layer comprising a leuco dye and a color developer as main constituents is provided. Since such a low- density synthetic paper has an excellent heat-insulating property, thermal energy supplied by a thermal head can be effectively absorbed into the thermal color forming layer. Thus, a thermal recording material enhanced in thermal sensitivity can be obtained. The synthetic paper is preferably produced by a film- forming method by using a thermoplastic resin based on a polyolefin, polystyrene, polyvinyl chloride or the like as a main raw material.

Description

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

[Prior art]

It has been known for a long time that color-forming leuco dyes, which are normally colorless or light-colored, and color developers such as organic acidic substances melt and react when heated, producing color. Examples of applications of this color-forming reaction to recording paper are published in Japanese Patent Publication No. 43-4160, Publication No. 45-
It is disclosed in Japanese Patent No. 14039 and the like and is well known. These thermal recording sheets are used in a wide range of fields, including measurement recorders, computer terminal printers, facsimile machines, automatic ticket vending machines, and barcode labels.
Recently, as these recording devices have become more diversified and more sophisticated, the quality required for heat-sensitive recording sheets has also become more sophisticated. For example, as the speed of thermal heads increases, there is a demand for thermal recording sheets that can record high-density, clear images even with minute thermal energy and that have good head matching properties such as sticking and head dregs.

The coloring of the heat-sensitive recording sheet is caused by a reaction in which the color-forming leuco dye and/or the color developer are dissolved by thermal energy supplied from the thermal head.
One way to improve color development sensitivity is to add a compound (generally called a thermofusible substance) that melts at a lower temperature than the leuco dye and color developer and has a high ability to dissolve both. It is widely known, and various compounds are disclosed in the following publications. For example, JP-A-49-3484
Publication No. 2 contains acetamide, stearamide, m −
Nitrogen-containing compounds such as nitroaniline and dinitrile phthalate are disclosed, acetoacetanilide is disclosed in JP-A-52-106746, and alkylated biphenyl alkanes are disclosed in JP-A-53-39139.

However, in recent years, especially in the thermal facsimile field, speeds have increased, and it has become common to drive the thermal head at high speed. Therefore, it has become a challenge to increase the dynamic color development sensitivity without lowering the color development start temperature. However, although the above compounds improve the static coloring sensitivity, sufficient dynamic coloring sensitivity cannot be obtained unless they are added in large quantities to the thermosensitive coloring layer. ), or
If sticking occurs or if the melting point is too low, the storage stability (background fog) on the heat-sensitive recording sheet 1 will be reduced, making it impossible to obtain fully satisfactory results.

In addition, one method for improving dynamic coloring sensitivity is to improve the smoothness of the surface of the thermosensitive coloring layer, or to add components that do not participate in the coloring reaction in the coloring layer, such as fillers and binders containing r-M. There is also a method of reducing the amount and increasing the density of the coloring component. Improving the surface smoothness can be easily achieved by calendering using a super calender or the like, but this can cause the background color to develop and the surface gloss to be high, which greatly impairs the appearance of the paper as a recording paper. . Note that fillers such as calcium carbonate, clay, urea-formalin resin, etc. are usually added to the heat-sensitive coloring layer to maintain the whiteness of the background, to prevent adhesion of residue to the head, and to prevent sticking. A water-soluble binder is added to fix the additives to the support, but reducing the content of these binders will inevitably lead to deterioration of the quality described above and cause inconveniences, so this method is not fully satisfactory. I can't get good results.

Furthermore, for the purpose of effectively utilizing the energy from the thermal head, it has been proposed to provide a heat insulating layer between the support and the heat-sensitive coloring layer, as described in, for example, JP-A-55-164192.
No. 59-5093 and No. 59-171685. However, with these, the smoothness of the surface of the heat insulating layer is significantly impaired, making it difficult to obtain a uniform image and not achieving satisfactory results. It has been proposed to improve thermal sensitivity by providing a laminated foam layer formed by foaming a filler and an undercoat layer containing a filler and a binder between the support and the thermosensitive coloring layer. However, this recording material has the disadvantage that it is accompanied by an increase in cost due to the complexity of the manufacturing process.

〔the purpose〕

An object of the present invention is to provide a heat-sensitive recording material with high dynamic color density that can record clear images with high density even with minute thermal energy without impairing other properties such as sticking or head matching properties. It is in.

〔composition〕

According to the present invention, there is provided a heat-sensitive recording material comprising a heat-sensitive coloring layer containing a leuco dye and a color developer as main components on a support, the support having a density of 0.90 g/cm or less. A heat-sensitive recording material is provided, which is characterized in that it is a synthetic paper.

The heat-sensitive recording material of the present invention has a density of 0.90 g as a support.
/aj or less, such low-density synthetic paper has excellent heat insulation properties, so the thermal energy from the thermal head can be effectively absorbed by the thermosensitive coloring layer, As a result, a heat-sensitive recording material with improved heat sensitivity can be obtained.

The synthetic paper used as a support in the present invention has a density of 0.90 g/- or less, and a density of 0.40-0.
A range of 90 g/clj is preferred. Density 0, 9
If synthetic paper with a content exceeding 0 g/al is used, its heat insulating properties will be insufficient and a product with high heat sensitivity will not be obtained.

Particularly preferable synthetic papers for use in the present invention are:
The porosity below the surface of the synthetic paper is 50% or more, preferably 50%.
Synthetic paper has a layer containing minute hollows in the range of ~9 brocades and has an overall density of 0.40 to 0.90 g/a+? It is a synthetic paper.

The synthetic paper used in the present invention is mainly made from conventionally known thermoplastic resins such as polyolefin, polystyrene, or polyvinyl chloride, and is produced by fiber method and film method (extrusion method, surface treatment method, etc.). Any material having a density within the above-mentioned range can be used as long as it is manufactured by a method such as a surface coating method or a surface coating method. However, from the point of view of surface smoothness, those manufactured by the film method are preferable.

For example, a synthetic paper produced by using a polyolefin resin as a main raw material, blending an inorganic filler and a small amount of additives, and using a biaxially stretched film forming method is preferably used. Note that the form of the synthetic paper is not limited to one in which both sides are bonded, but also one in which only one side is bonded.

In the present invention, on the support made of the synthetic paper,
A heat-sensitive coloring layer containing a commonly used known leuco dye and a color developer as main components is provided.

The leuco dyes used in the present invention can be applied singly or in combination of two or more types, but such leuco dyes include:
Those applied to this type of heat-sensitive material can be arbitrarily applied. For example, leuco compounds of dyes such as triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, and indolinophthalide-based dyes are preferably used. . Specific examples of such leuco dyes include those shown below.

3.3-bis(p-diethylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis(p-dimethyl (aminophenyl)-6-diethylaminophenyl.

3.3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3.3-bis(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-(N-p-tolyl-N-ditylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- (N-(3'-trifluoromethylphenyl)
amino)-6-dinithylaminofluorane, 2-(3
, 6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(m-h-lichloromethylanilino)fluoran, 3-diethylamino-7-( o-chloroanilino)fluoran, 3-dibutylamino-7-(o-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-(N,N-diethylamino )-5-methyl-7-(
N.

N-dibenzylamino)fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane.

3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3- (2'-Methoxy-5'-nitrophenyl)phthalide, 3-(2'-hydroxy-4'-diethylaminophenyl)-3-(2'-methoxy-5'-methylphenyl)phthalide, 3-(2 '-methoxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-5'
-methylphenyl)phthalide, 3-(N-ethyl-N-i-amyl)amino-6-methyl-7-anilitufluorane, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl- 7-anirite fluorane, 3-(N-
Ethyl-N-ethoxypropyl)amino-6-methyl-
7-anirite fluorane, 3-(N-methyl-N-isopropyl)amino-6-methyl-7-anirite fluorane, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3- Pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methyl Aminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluoran, 3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluoran, 3-diethylamino- 7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p-n
-butylanilino)fluoran, 3-(N-benzyl-N-cyclohexylamino)-5
, 6-penzo 7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino 4
',5'-benzofluorane etc.

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

gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-tar
t-Butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid, 4,4'-isopropylidene diphenol, 4,4'-isopropylidene bis(2-chlorophenol), 4,4'-isopropylidene bis (2,6-
dibromophenol), 4,4'-isopropylidene bis(2,6-dichlorophenol), 4,4'-isopropylidene bis(2-methylphenol), 4,4'-
Isopropylidene bis(2,6-dimethylphenol)
, 4,4'-isopropylidene bis(2-tart-butylphenol), 4,4'-5ee-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, novolak type phenolic resin, 2.2 '-Thiobis(4,6-dichlorophenol), catechol, resorcinol, hydroquinone, pyrogallol, phloroglycin, phloroglycin carboxylic acid, 4-tart-octylcatechol, 2,2'
-methylenebis(4-chlorophenol), 2,2'-
Methylenebis(4-methyl-6tert-butylphenol), 2,2'-dihydroxydiphenyl, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, ρ-hydroxy P-chlorobenzyl benzoate, p-hydroxybenzoate-〇-chlorobenzyl, p-methylbenzyl p-hydroxybenzoate, P
-n-octyl hydroxybenzoate, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-6-naphthoic acid substituent, 4-hydroxydiphenylsulfone, 4-
Hydroxy-4'-chlorodiphenylsulfone, bis(
4-Hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, zinc 3,5-di-tart-butylsalicylate, tin 3,5-di-tart-butylsalicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid Acid, stearic acid, 4-hydroxyphthalic acid, boric acid,
Thiourea derivatives, 4-hydroxythiophenol derivatives, etc., bis(4-hydroxyphenyl)acetic acid, bis(4-hydroxyphenyl)
hydroxyphenyl) methyl acetate.

Bis(4-hydroxyphenyl)ethyl acetate, bis(4-hydroxyphenyl)ethyl acetate
-Hydroxyphenyl) n-propyl acetate, bis(4-
Hydroxyphenyl)n-butyl acetate, bis(4-hydroxyphenyl)phenyl acetate, bis(4-hydroxyphenyl)benzyl acetate, bis(4-hydroxyphenyl)phenethyl acetate, bis(3-methyl-4-hydroxyphenyl)acetic acid , methyl bis(3-methyl-4-hydroxyphenyl)acetate, ethyl bis(3-methyl-4-hydroxyphenyl)acetate, n-propyl bis(3-methyl-4-hydroxyphenyl)acetate, 1,7- Screw(
4-hydroxyphenylthio)3,5-dioxahebutane, 1,5-di(4-hydroxyphenylthio)-3-
Oxapentane, dimethyl 4-hydroxyphthalate, 4
-Hydroxy-4'-methoxydiphenylsulfone, 4
-Hydroxy-4'-ethoxydiphenylsulfone, 4
-Hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-n-propoxydiphenylsulfone, 4-hydroxy-4'-n-butoxydiphenylsulfone, 4-hydroxy-4'-isobutoxydiphenylsulfone, 4 -Hydroxy-4'-5ac-butoxydiphenylsulfone, 4-hydroxy-4'-t
arbutoxydiphenylsulfone, 4-hydroxy-4
'-Benzyloxydiphenylsulfone, 4-hydroxy-4'-phenoxydiphenylsulfone, 4-hydroxy-4'-(m-methylbenzyloxy)diphenylsulfone, 4-hydroxy-4'-(p-methylbenzyloxy)diphenyl Sulfone, 4-hydroxy-4'-(
o-methylbenzyloxy)diphenylsulfone, 4-hydroxy-4'-(p-chlorobenzyloxy)diphenylsulfone, and the like.

In the present invention, various commonly used binders can be used as appropriate to bind and support the leuco dye and color developer on the support, such as polyvinyl alcohol, starch and its derivatives, methoxy cellulose, hydroxyethyl cellulose. , cellulose derivatives such as carboxymethylcellulose, methylcellulose, and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide/acrylic acid ester copolymer, acrylamide/acrylic acid ester/methacrylic acid terpolymer, styrene/maleic anhydride copolymer Combined alkali salt, inbutylene/maleic anhydride copolymer alkali salt,
In addition to water-soluble polymers such as polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic ester, vinyl chloride/vinyl acetate copolymer, and Latex such as butyl methacrylate, ethylene/vinyl acetate copolymer, styrene/butadiene/acrylic copolymer, etc. can be used.

In addition, in the present invention, in addition to the leuco dye and color developer, if necessary, auxiliary additive components commonly used in this type of heat-sensitive recording material, such as fillers, surfactants,
A thermofusible substance (or lubricant), etc. can be used in combination.

In this case, fillers include 1, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium and silica. , urea-formalin resin, styrene/methacrylic acid copolymer, polystyrene resin, and other organic fine powders. Examples of thermofusible substances include higher fatty acids or their esters, amides, or metal salts. In addition, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, 3,4-
Examples include dialkyl epoxy-hexahydrophthalate, higher ketones, and other heat-fusible organic compounds having a melting point of about 50 to 200°C.

In addition, in the present invention, between the support and the thermosensitive coloring layer,
If necessary, a layer containing a filler and a binder may be provided as an undercoat layer. In this case, specific examples of the filler and binder include those exemplified in the heat-sensitive coloring layer.

Furthermore, in the heat-sensitive recording material of the present invention, a protective layer can be provided on the heat-sensitive coloring layer for the purpose of improving the matching properties of thermal heads, etc., and further enhancing the storage stability of recorded images. The above-mentioned fillers, binders, surfactants, and thermofusible substances can also be used as components constituting the protective layer.

〔effect〕

The heat-sensitive recording material of the present invention uses synthetic paper having a density in a specific range as a support, so that thermal energy from the thermal head can be used with increased efficiency for the melting reaction of the heat-sensitive coloring layer. As a result, the thermal sensitivity of the product is improved.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that all parts and percentages shown below are based on weight.

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

(A) Liquid composition 10% polyvinyl alcohol aqueous solution 16 parts water

64 parts CB) Composition Benzyl p-oxybenzoate 20 parts Calcium carbonate 10 parts IO% polyvinyl alcohol aqueous solution 30 parts Water
40 parts Next, (A) liquid: (Bl liquid = 1:4 weight ratio) Both were mixed and stirred to obtain a thermosensitive coloring layer forming liquid.

This heat-sensitive coloring layer forming liquid was applied to synthetic paper with a density of 0.77 g/- [Product name: Yupo FPG #60; Oji Yuka Synthetic Paper It$
The dry adhesion amount is 3.0 to 4.0 g/r on the surface of
rr, and after drying, it is calendered using a super calender so that the gloss level (measured according to JIS-P-8142) is 10-13%. A thermosensitive recording sheet (C-1) was obtained.

Example 2 The method of the present invention was carried out in the same manner as in Example 1, except that synthetic paper with a density of 0.83/cIf [trade name: Yubo SGG #60; manufactured by Oji Yuka Synthetic Paper ■] was used as the support. A thermosensitive recording sheet (C-2) was obtained.

Comparative Examples 1 and 2 Synthetic paper with a density of 0.92 g/cII was used as the support.
Example except that product name: Yubo TPG 160: manufactured by Tamago Oil Chemical Synthetic Paper @] and density 0.96 g/cd (7) synthetic paper [product name: Peach Coat WG-140; manufactured by Nisshinbo ■] were used. In the same manner as in 1, a comparative heat-sensitive recording sheet (D-
1 and D-2) were obtained.

Comparative Example 3 Commercially available high-quality paper (density 0.85 g/cat) as support
A comparative heat-sensitive recording sheet (D-3) was obtained in the same manner as in Example 1 except that .

Regarding each heat-sensitive recording sheet obtained as above,
The dynamic color development sensitivity was tested using a G-m facsimile test machine. The results are shown in Table-1.

The test machine was an 8dot/- manufactured by Kensei Electronic Parts Co., Ltd.
The heating resistor has a thermal head of approximately 200Ω/
The main scanning recording speed is Ionsec/1.
The test was conducted under three conditions: 0, 5 m5 ec, 0.35 m5 ec, and 0.25 m5 ec under the following conditions: ine, sub-scanning line density of 7.71 ine/nm, head input of 0.6 w/dot. In addition, the sticking property was improved to 1.8 m.
Tested with 5ec all solids. The concentration is measured using the Macbeth densitometer (
It was measured using RD-514 and filter ratten-106).

Table 1 As can be seen from Table 1 above, it can be seen that the heat-sensitive recording material of the present invention provides a high degree of color development with extremely small thermal energy. Further, there was no sticking in the image, and it was confirmed that the image had extremely good head matching properties.

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a heat-sensitive coloring layer containing a leuco dye and a color developer as main components is provided on a support, the support is synthetic paper with a density of 0.90 g/cm^3 or less. A heat-sensitive recording material characterized by: