JPS59158288A - Thermal recording material - Google Patents

Abstract

PURPOSE:To provide a highly reliable thermal recording material with an image stability by arranging a leuco dye, a specified developer and a hot-melting substance. CONSTITUTION:1wt.pt. of a leuco dye (e.g., 3,3'-bis(p-dimethyl aminophenyl)-6-dimethyl aminophtharide), 4-10wt.pts. of one or more kinds of develoeprs selected from among ZuCl2, AlCl3, ZuBr2 and AlBr3 and 5-30wt.pts. of a hot-melting material with the melting point of 60-150 deg.C (e.g. stearic acid amide) as required, a binder (e.g. PVA), a filler (e.g. CaCO3), a lubricant and the like are dispersed or dissolved into water to obtain a liquid coat. Then, said liquid coat is applied on a support up-to 2-10g/m<2> in the thickness and dried to form a thermographic layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an improved heat-sensitive recording material containing a leuco dye as a color former and a specific metal halide as a color developer.

[Prior art]

In recent years, thermal recording methods have been widely adopted to cope with the increase in the amount of information and to meet social demands such as resource saving, labor saving, and pollution-free production. The heat-sensitive recording material used in this heat-sensitive recording method generally has a heat-sensitive coloring layer containing a thermocolorable composition as a main component on a support such as paper, synthetic paper, or plastic film. Colored images can be obtained by heating with a pen, laser light, strobe lamp, etc. . Compared to other recording materials, this type of recording material does not require complicated processing such as development and fixing, and records can be obtained in a short time using relatively simple equipment.1. Due to its advantages such as low noise generation, low environmental pollution, and low cost, it is generally widely used for copying documents such as books and documents, and is also used for special purposes such as electronic computers, facsimiles, ticket vending machines, labels, and radar. It is widely used as a recording material in many fields.

Thermochromic compositions used in such heat-sensitive recording materials generally consist of a color former and a color developer that causes the color former to develop color when heated; Light-colored leuco dyes and organic acids and phenolic substances have conventionally been used as color developers. A recording material that combines a color forming agent and a color developing agent has the advantage that the resulting image has a particularly clear color tone, has a high degree of background whiteness, has excellent brightness, and has excellent light fastness. , is widely used.

However, in recent years, there have been cases in which images with this type of recording material fade during storage, which has become a problem, particularly from the aspect of image reliability. Therefore, there has been a strong demand in the technical field for the development of heat-sensitive recording materials that exhibit reliable image stability.

[Object] In view of the above circumstances, an object of the present invention is to provide an improved heat-sensitive recording material that exhibits reliable image stability.

Another object of the present invention is to provide a novel heat-sensitive recording material containing a specific metal halogenide as a color developer and, if desired, a thermofusible substance as an auxiliary agent.

〔composition〕

As a result of extensive research aimed at solving the above-mentioned problems with conventional heat-sensitive recording materials, the present inventors surprisingly discovered that zinc chloride, aluminum chloride, zinc bromide and It has been found that by using 4 to 10 parts by weight of at least one metal halide selected from the group consisting of aluminum chloride per 1 part by weight of the dye, it is possible to achieve a previously unexpected high image density and improvement in image stability. Ta. Furthermore, it has been found that when a thermofusible substance having a melting point of 60 DEG to 150 DEG C. is used in combination with the metal halide described above, image stability, especially density, is further improved. The present invention was completed based on these findings.

According to the present invention, in a heat-sensitive recording material containing a leuco dye and a color developer, the color developer is a metal chloride selected from the group consisting of zinc chloride, aluminum chloride, zinc bromide, and aluminum bromide. is present in a ratio of 4 to 10 parts by weight per 1 part by weight of the leuco dye, and if desired, a thermofusible substance having a melting point of 60 to 150° C. is present. A thermosensitive recording material is provided.

It is well known that zinc chloride has thermal color development properties for leuco dyes. However, there is a problem in that a satisfactory image density cannot be obtained due to the use of zinc chloride.

The present inventors focused on quantitative issues when using metal chloride such as zinc chloride as a color developer, and as a result of repeated studies, we decided to use bisphenol A, which is conventionally used as a color developer. The concentration of phenolic compounds such as If the seed is used in an amount slightly less than 4 parts by weight per 1 part by weight of the leuco dye, a satisfactory concentration cannot be obtained, and if it is used in an amount greater than 10 parts by weight, the coloring of the skin becomes intense. However, it has been found that when used in an amount of 4 to 10 parts by weight, both density and image stability are significantly improved. In addition, the metal halide has 60 to 15
By using a thermofusible substance with a melting point of 0℃,
It has also been found that even better concentrations can be obtained.

Zinc compounds other than zinc chloride and zinc bromide used as a thermal color developer in the present invention, such as zinc oxide, zinc hydroxide,
Sulfuric acid, zinc oxide, zinc nitrate, zinc carbonate, zinc butoxide, zinc oxalate, etc., almost never give an effective concentration; on the other hand,
It is interesting that even when various aluminum compounds other than aluminum chloride and aluminum bromide are used, for example aluminum compounds corresponding to the zinc compounds mentioned above, satisfactory concentrations are hardly obtained. Furthermore, it has been found that ammonia complexes derived from zinc chloride and complexes with organic bases such as HMPA (hexamethylene phosphatamine) provide extremely low concentrations compared to zinc chloride and cannot be used in practice. It is therefore a completely unexpected and valuable discovery in the present invention that the use of 4 to 10 parts by weight of said metal halide per part by weight of leuco dye provides a satisfactorily high concentration.

The colorless or light-colored leuco dyes used in the heat-sensitive recording material of the present invention are known per se, and are used alone or in the form of a mixture of two or more of them as color formers. 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 compounds.

3.3'-bis(p-dimethylaminophenyl)-6-
Cynotylaminophthalide (also known as crystal violet), 3.3-bis<p-,>methylaminophenyl)phthalide, 3.3-bis(p-dimethylaminophenyl)phthalide, 3.3-bis(p -dimethylaminophenyl)-6-dimethylaminophenyl, 3.3-bis(p-)methylaminophenyl) = 6-chlorophthalide, a-(N-p-)dyl-N-ethylamino)-6-methyl- 7-anilinofluorane, 3-diethylamino-7
-Chlorofluorane, a--(N-n-hexyl-N
-Methylamine) = 6-methyl-7-anilinofluorane, 3-diethylami/-7-(o-chloroanilino)fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino- 7-(0-chloroanilino)-fluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-(m-trichloromethylanilino)fluoran, indiylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrylosbilane, 6'-7''lomo3'-methoxybenzoindolino-
Byrillospiran and 2-[3,6-bis(diethylamino)-9-[0-chloroanilino)]xantylbenzoic acid lactam.

The color developer used in the heat-sensitive recording material of the present invention for the purpose of thermally developing the leuco dye is at least a metal nologen selected from the group consisting of zinc chloride, aluminum chloride, zinc bromide, and aluminum bromide. Although it is one type, an appropriate amount of a conventional color developer can also be used in combination.

Suitable customary color developers that can be used in combination include, in particular, bisphenol compounds, such as 4,4'-isopropylidenebisphenol 4,4'-
Isopropylidene bis(0-methylphenol), 4.4'-Secondary-butylidene bisphenol, 4
．． 4'-isopropylidene bis(2-ternya1-nobutylphenol), 4.4'-cyclohexylidene diphenol, 4.4'
-Inozolopylidene bis(2-chlorophenol), 2.2'-methylenebis(4-methyl-6-tert-butylphenol), 2.2'-methylenebis(4-ethyl-6-tert-butylphenol), 4 .4'-Butylidene bis(6-tert-butyl-
m-cresol) and 4,4'-thiobis(6-tert-butyl-m-cresol), but also phenolic compounds such as isopropyl p-hydroxybenzoate, inbutyl p-hydroxybenzoate, Examples include benzyl -hydroxy-7benzoate, cyclohexyl p-hydroxybenzoate, neopentyl p-hydroquinebenzoate, catecholditylphenone, propyl furotocatechuate (ester), benzyl protocatechuate, propyl gallate, and stearyl gallate.

In the heat-sensitive recording material of the present invention, the thermofusible substances having a melting point of 60 to 150°C that can be used in combination with the metal logenide color developer are higher fatty acids, higher fatty acid esters, higher fatty acid amides, and higher fatty acids. Selected from metal salts, acid amides of higher aliphatic amines, phthalic acid amide compounds, animal waxes, mineral waxes, vegetable waxes, petroleum waxes, alkylnaphthalene compounds, diphenyl derivatives, triphenyl derivatives, benzoic acid esters, etc. but,
Typical examples include stearic acid amide, palmitic acid amide, zinc stearate, phthalic acid, distearylamide, isophthalic acid distearylamide, phthalic acid laurylamide, 2.6-)isozolopyrnaphthalene, 6, 7-,)
Methylnaphthalene, p-benzyldiphenyl, benzoic acid p-chlorophenyl ester, benzoic acid (p-
Examples include ethoxycarbonylphenyl ester, octadecylcarbamoylbenzene, and octadecyl (p-methoxycarbonylbamoylbenzene). It goes without saying that one is not only exposed to the above-mentioned compounds.

The heat-sensitive recording layer contains conventional binders, fillers, surfactants,
It can contain lubricants and the like. In this case, as a binder, for example, in addition to water-soluble resins such as polyvinyl alcohol hydroxyethyl cellulose, methyl cellulose, isobutylene/maleic anhydride copolymer alkali salt, polyurethane styrene/butadiene copolymer, polyacrylic acid ester, etc. Latex can also be used.

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

To produce the heat-sensitive recording material of the present invention, a leuco dye, a color developer, a binder, and, if necessary, the above-mentioned thermofusible substance are added as main components to a support such as paper, synthetic paper, or plastic film. All you have to do is apply an aqueous solution and dry it. The amounts of the leuco dye, thermofusible substance, and binder used are 5 to 30% by weight, 0 to 60% by weight, and -2 to 20% by weight, respectively. In addition, the adhesion amount of the thermosensitive coloring layer to be formed is 2 to 1oP.
/71', preferably 3 to 7 P/m'.

When using the heat-sensitive recording material of the present invention, organic solvents such as
Even when it comes into contact with ethyl alcohol, acetin, etc., not only does the image not fade, but there is also almost no coloration on the background, and the contrast is almost the same as before contact. Further, even if it comes into contact with oils and fats, such as tempura oil, salad oil, machine oil, olive oil, etc., there is almost no change in the image or the background.

Furthermore, even when overlaid with plasticizer or softener-added plastic wrap or eraser, the image and background hardly change, which is a feature and advantage not found in conventional heat-sensitive recording materials.

The invention will be explained in further detail by the examples below.

In the examples, parts and parts indicate parts by weight, respectively.

Example 1 [Liquid A] 3-(N-methyl-N-cyclohexylamino) = 6-
Methyl-7-anirite fluorane 10 parts 10% aqueous solution of hydroxyethyl cellulose 10/7
water
30〃Dispersed in a ball mill to reduce the average particle size to 5μ or less.

[Liquid B]

Urea formalin resin fine particles 2
0 parts Stearic acid amide 15
Zinc stearate 51/Polyvinyl alcohol 10% aqueous solution 40〃
water
The particles were dispersed in a 150 mm Seel mill to have an average particle size of 5 μm or less.

[Liquid C]

Color developer shown in the (Compound A) column of Table-1 30
10 parts polyvinyl alcohol aqueous solution 3 parts
0 water
90 Water-soluble compounds are used after being dissolved, but
Water-insoluble compounds are dispersed in a ball mill to reduce the average particle size to 5.
I made it less than μ.

The above-mentioned Agl1. (contains leuco dye), B liquid and C
When mixing the liquid (developer), Cg! By adjusting the amount of L, the ratio of leuco dye to color developer was adjusted as shown in Table 1 below. This mixed solution was coated and dried on high-quality paper with a basis weight of 50", and at this time, the dry adhesion amount of leuco dye was 0.5 fi-/m", and a heat-sensitive coloring layer was provided. produced paper. The evaluation results of the thermal recording are shown in Table 1 below. Note that the maximum concentration (Dmax) is
The image density is the image density when printed at 130° C. using a commercially available thermal gradient tester, and the background density (Dmin) at that time is also shown. The concentration is 1~ measured using a Macbeth densitometer.

In addition, oil resistance can be tested by applying 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. Plasticity resistance is 50% when layered on the surface of polyvinyl chloride wrap thermosensitive coloring layer.
A load of 0 ficni was applied and the change was observed after being left for one day.

As is clear from the results shown in Table 1, the image quality and stability of the material vary significantly depending on the type of color developer and its ratio to the leuco dye. It can be seen that satisfactory high density and reliable image stability can be obtained.

Example 2 [Liquid A] 10% aqueous solution of hydroxyethyl cellulose 1 ott
water
The particles were dispersed in a 30" Zeel mill to have an average particle size of 5 microns or less.

[Liquid B]

Urea formalin resin fine particles 2
Fusible substance shown in the (Compound A) column of Part 0 Table-2
15〃Zinc stearate 5
〃Polyvinyl alcohol 10% aqueous solution 4
0//Wed
150〃Dispersed with a ball mill to reduce the average particle size to 5
I made it less than μ.

[Liquid C]

Color developer shown in the (Compound B) column of Table-2 30
Part polyvinyl alcohol 10% aqueous solution
30 water
90 Water-soluble compounds are used after being dissolved, but
Water-insoluble compounds are dispersed in a Zeel mill to reduce the average particle size to 5.
I made it less than μ.

When mixing the A solution containing the leuco dye, the B solution containing the thermofusible substance, and the C solution containing the color developer obtained as follows, adjust the amount of C'gf. The ratio of leuco dye and color developer was prepared as shown in Table 2 below. This mixed solution was applied onto high-quality paper with a basis weight of 50 f/m' and dried.
At this time, a heat-sensitive recording paper with a heat-sensitive coloring layer was manufactured so that the amount of leuco dye deposited was 0.5.77 m''.The evaluation results of the heat-sensitive recording are shown in Table 2 below.
The maximum concentration (Dmax) was determined using a commercially available thermal gradient tester.
The image density when printed at 30° C. is shown, and the background density (Dmjn) 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.
The judgment was made by observing changes after being left in a constant temperature bath for 3 days. Plasticity resistance is determined by layering on the surface of the polyvinyl chloride wrap heat-sensitive coloring layer.
Judgment was made by observing changes after applying a load of 00P/ca and leaving it for one day.

As is clear from the results shown in Margin Table 2 below, in the heat-sensitive recording material of the present invention, "(Compound A) the metal halide color developer shown in Column J" was added to "(Compound B) the heat shown in Column J". It can be seen that by using a fusible substance in combination, the image density and image reliability are improved compared to the case of not using the fusible substance and the case of a heat-sensitive recording material not according to the present invention.

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

Claims (2)

[Claims] (1) In a heat-sensitive recording material containing a leuco dye and a color developer, at least one metal halide selected from the group consisting of zinc chloride, aluminum chloride, zinc bromide, and aluminum bromide is used as the color developer. A heat-sensitive recording material characterized in that the leuco dye is present in an amount of 4 to 10 parts by weight per 1 part by weight. (2) In a heat-sensitive recording material containing a leuco dye and a color developer, at least one metal halide selected from the group consisting of zinc chloride, aluminum chloride, zinc bromide, and aluminum bromide is used as the color developer. Present in a proportion of 4 to 10 parts by weight per 1 part by weight of the leuco dye,
A heat-sensitive recording material further comprising a thermofusible substance having a melting point of 60 to 150°C.