JPS5938091A - Heat sensitive recording - Google Patents

Abstract

PURPOSE:To improve the solvent resistance and stability of images to be obtained by using aluminum chloride as at least a part of a color developer in a heat-sensitive recording material containing a leuco dye as color forming agent. CONSTITUTION:An aqueous solution containing 5-30wt% of a color forming agent employing a colorless or light-colored leuco dye such as triphenyl methane, fluorane and phenothiazine compounds in the single or mixed form, 40-80wt% of color developer containing aluminum chloride, 2-20wt% of a binder such as polyvinyl alcohol, hydroxy ethylcellulose and a filler, a surfactant and the like as required is applied and dried on a support to form a thermal color forming layer. The color developer usually jointly uses in an adequate amount other types such as commonly used phenol compound in addition to the aluminum chloride.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in heat-sensitive recording materials containing leuco dyes as color formers.

Thermosensitive recording materials generally have a thermosensitive coloring layer containing a thermochromic composition as a main component on a support such as paper, synthetic paper, or plastic film.
A colored image can be obtained by heating with a straw lamp or the like. Compared to other recording materials, this type of recording material
It has the advantages of being able to obtain records in a short time with a relatively simple device without complicated processes such as fixing, generating less noise and polluting the environment, and being inexpensive.
In addition to being used for copying books, documents, etc., it is also widely used as a recording material in a variety of fields such as electronic computers, facsimiles, ticket vending machines, labels, and recorders. The composition generally consists of a color former and a color developer that causes the color former to develop color when heated.
As color formers, for example, colorless or light-colored leuco dyes containing lactone, lactam or spiropyran rings have been used, and as color developers, organic acids and phenolic substances have been conventionally used. This recording material that combines a color former and a color developer has the advantage that the resulting image has a clear color tone, has a high background whiteness, has excellent brightness, and has excellent light fastness. Widely used.

However, on the other hand, the image of this recording material may develop color or fade when it comes into contact with organic solvents, plasticizers, oils and fats, resulting in a loss of contrast, and the reliability of the image becomes unreliable. It is also true that enough is enough.

Phenolic substances such as bisphenol A have the property of decolorizing images when they come into contact with wrap films such as polyvinyl chloride, which has recently become a problem.

In order to solve these problems, the present inventors have conducted extensive research and have found that by using aluminum chloride as a color developer for leuco dyes, they have been able to achieve an improvement in image stability that was previously unachievable. This discovery led to the completion of the present invention.

That is, according to the present invention, in a heat-sensitive recording material in which a leuco dye and a color developer for the leuco dye are supported on a support, aluminum chloride is used as at least a part of the color developer. Recording materials will be provided.

To describe the present invention in more detail, when the heat-sensitive recording material of the present invention is used, not only will the image not be discolored even when it comes into contact with an organic solvent such as ethyl alcohol or acetone, but the background color will not develop and the contrast will be reduced. , no different from before contact. Also, there is almost no change in oil. In addition, even when layered with plasticizer or softener-added plastic wrap or eraser, the image and background hardly change, an unprecedented characteristic.

The colorless or light-colored L1 icodye used in the present invention may be used alone or in combination as a coloring agent.

Examples of the leuco dye include triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based dyes, and specific examples thereof include the following: 3,3'- Hx (p-') methylaminonoenyl)-6-dimethylaminophthalide (also known as crystal ζ
iolet), 3, "3-bis(p-dimethylaminophenyl) phthalide, 3.3-bis(p-dimethylaminophenyl) phthalide, 3.3-?"su(p, dimethylaminophenyl)-6
-dimethylaminophenyl, a,3-bis(p-imethylaminoneenyl-6-chlorophthalide, 3-(N-p-tolyl-N-ethylamino)-6-methyl-7-anilinofluorane,

3-diethylamine-7-chlorofluorane, 3-(N
-cyclohexyl-N-mewareamino)-6-methyl-
7-anilinofluorane, 3--)ethylamino-7-
(o-ri0roanili←fluoran, 3-diethylamino-6-methyl-7-ani□rithufluoran, 3--)butyltemino-? ” (o-ri□口Oanilino)-fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluorane, □be /zoyl a icomethylenesol, 6'-chloro-8'-methoxy-benzoindolino-bilirosbilane, 6'-fomo3'-methoxybency/deU/-pyrylospirane, 2-(3,6 -bis(diethylamino)-9-(o-
chloroanilino)] xa/tylbenzoic acid lactam, etc.

In the present invention, aluminum chloride is used as a color developer, but in this case, an appropriate amount of a conventional color developer can be used in combination. Preferred color developers used in combination include phenolic substances such as 4,4'-isozolobylidene bisphenol, 4,4'-isopropylidene bis(0-methylphenol), and 4,4'-secanda. Liebtylidenepisphenol,
4,4'-isozolobylidene bis(2-1-shari-butylphenol), 4,4'-cyclohexylidene diphenol, 4,4'-isomer-10pylidene bis(2-
10rophe""), 212'-methylenebis(4-methyl-6-tertiarywotylphenol), 2.2'-
methylenebis'<4-ethyl-6-tertiarybutylphenol), 4,4'-zotylidenebis(6-tertiary-butyl-m-cresol), 4,4'-thiobis(6-tertiarybutyl- m-cresol), ξ
Isozorobyl thioxybenzoate, isobutyl p-oxybenzoate, benzyl p-oxybenzoate, cyclohexyl p-oxybenzoate, neopentylcatechol butylphenone p-oxybenzoate, propyl protocatechuate (ester), hensyl protocatechuate, gallic acid Examples include propyl and stearyl gallate.

The heat-sensitive recording layer may contain a binder, a filler, a surfactant, a lubricant, and the like. In this case, as the binder, a latex such as phorinyl alcohol, hydroxyethyl cellulose, styrene/butadiene copolymer, or polyacrylic acid ester can be used.

In addition, fillers include inorganic substances such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, clay, and talc, as well as urea-formalin resin,
An organic filler made of fine particles of polystyrene or the like can be used. As the lubricant, in addition to higher fatty acids, their esters, amides, and metal salts, various wax-like substances can be used.

The heat-sensitive recording material of the present invention can be prepared by applying an aqueous solution containing a leuco dye, a color developer, and a binder as main components to a support such as paper or synthetic paper and drying it. Here, the amounts of leuco dye, color developer and binder used are 5 to 30% by weight and 40 to 80% by weight, respectively.
0 to 80% by weight and 0% by weight are suitable. The adhesion amount of the thermosensitive coloring layer to be formed is suitably about 2 to 1Of/rn''.

Examples are shown below. Note that parts and units are parts by weight and parts by weight, respectively.

Example [Liquid A] LOS aqueous solution of hydroxyethyl cellulose t
o part water
30 parts were dispersed in a dill mill to reduce the average particle size to 5 μm or less.

[Liquid B]

Urea formalin resin fine particles 20 parts stearamide 15 parts zinc stearate 5M polyvinyl alcohol xo% aqueous solution 4o parts water
150 parts were dispersed in a Zeel mill to have an average particle size of 5 μm or less.

[Liquid C]

Group A compound in Table 1 15 parts polyvinyl alcohol 10% aqueous solution 15 parts water
4
The water-soluble compounds were dissolved and used in 5 parts, but the water-insoluble compounds were dispersed in a Dirumil to have an average particle size of 5 μm or less.

[Liquid D]

Group B compounds in Table 1 15 parts polyvinyl alcohol 10% aqueous solution 15 parts water
45 parts The water-soluble compounds were dissolved and used, but the water-insoluble compounds were dispersed in a Zeel mill to have an average particle size of 5 μm or less.

The A liquid, B liquid, C liquid and D liquid obtained as above were mixed in the manner shown in Table 1, and the dry adhesion amount was 67-/m'' on high-quality paper with a basis weight of 5゜P7m''. A heat-sensitive coloring layer was provided by coating and drying to obtain heat-sensitive recording paper. The evaluation results are shown in Table 2 below. Note that the maximum density is the image density when printed at 140° C. using a commercially available thermal gradient tester, and the background density (DM) at that time is also shown. Concentrations were measured using a Macbeth densitometer.

Oil resistance can be tested by applying a thin layer of cottonseed oil to the image area at 40°C.
Judgment was made by observing changes after being left in a constant temperature bath for 3 days. The plasticity resistance is determined by layering on the surface of the polyvinyl chloride wrap thermosensitive coloring layer.
Judgment was made by observing changes after applying a load of 0.00 t/cnl and leaving it for one day.

Table-1 ○... Almost no change △... Image density decreases a little ×...
As can be seen from the above results in which the image density is significantly reduced, when aluminum chloride is used as a color developer, the finger squeezing resistance and plasticizer resistance are significantly improved.

Patent applicant Ricoh Co., Ltd. Agent Patent Attorney Toshiaki Ikeura

Claims (1)

[Claims] (1) A heat-sensitive recording material comprising a leuco dye and a developer for the leuco dye supported on a support, characterized in that aluminum chloride is used as at least a portion of the developer.