JPH02192986A - Thermosensitive recording material - Google Patents

Abstract

PURPOSE:To ensure that the subject material is highly sensitive, reliable and exceedingly weather-proof by using a basic calcium compound or a basic magnesium compound as a filler, and specifying the pH value of the surface of a thermosensitive coloring layer. CONSTITUTION:A coloring layer containing leuco dye and a color developer is provided on a support, and a basic calcium compound or a basic magnesium compound is used as a filler. At the same time, the pH value of the surface of a thermosensitive coloring layer is set at 6 to 8. The basic calcium compound is, for instance, calcium silicate or calcium carbonate, and the basic magnesium compound is magnesium silicate, magnesium carbonate, magnesium hydroxide or magnesium oxide. If the pH value of the surface of the thermosensitive coloring layer is maintained at 6 to 8, the weather proofness of a thermosensitive recording material is significantly increased. If the pH value is 6 or less, a background fog generates and the background becomes darkened. On the contrary, if the pH value is 8 or more, a reaction upon a phenol compound occurs and the material becomes easily yellowish.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a heat-sensitive recording material, and more specifically to a heat-sensitive recording material that utilizes a color-forming reaction between a leuco dye that is colorless or slightly pale at room temperature and a color developer for the leuco dye. Concerning recording materials.

[Conventional technology]

Recently, various recording materials have been researched and developed and put into practical use in the information recording field, in response to social demands such as diversification and increase in information, resource conservation, and pollution-free technology.Among them, thermal recording materials are (1) A colored image is recorded simply by heating, eliminating the need for a complicated development process. (2) It can be produced using a relatively simple and compact device, and the resulting recording material is easy to handle. (3) paper is often used as the support;
In this case, not only the cost of the support is low, but also the feel of the resulting recorded material is similar to that of plain paper. It is widely used in the field of low and high speed facsimiles, automatic ticket vending machines, thermal copying, etc.

The above-mentioned heat-sensitive recording material is produced by applying and drying a heat-sensitive coloring layer liquid containing a coloring component capable of causing a coloring reaction when heated on a support such as ordinary paper, synthetic paper, or a synthetic resin film. A colored image is recorded on the heat-sensitive recording material thus obtained by heating it with a thermal pen or a thermal head.

Conventional examples of such heat-sensitive recording materials include, for example, the heat-sensitive recording materials disclosed in Japanese Patent Publication No. 43-4160 or Japanese Patent Publication No. 45-14039; Poor responsiveness.

Sufficient color density could not be obtained during high-speed recording.

As a method to improve this drawback, as a leuco dye,
One using 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane (Japanese Patent Application Laid-open No.
9-109120), one using 3-dibutylamino-6-methyl-7-anilinofluorane (Japanese Unexamined Patent Application Publication No. 1987-1999-
The development of highly sensitive dyes such as 1,7-bis(4-hydroxyphenylthio)-3,5-dioxahebutane (
1,5-bis(4-hydroxyphenylthio)-3-oxapentane (JP-A-59-106456)
9-116262), a heat-sensitive recording material that achieves higher speed and higher sensitivity has been disclosed. Also, attempts have been made to increase speed and sensitivity by combining the above-mentioned substances in JP-A-61-123584, JP-A-61-215087, and JP-A-61-242889.

At the same time, the image reliability required for thermal recording paper has also increased, and it has become more common for thermal recording paper to be displayed on walls for one or two months. At this time, there have been cases where the background has turned yellow or has a black fog, causing problems. As a solution to this kind of fogging, there is a
, JP 60-58714, JP 57-208297
, Japanese Patent Laid-Open No. 61-125879, etc., attempts have been made to neutralize the base paper and use a magnesium compound in the thermal layer, but at present it is not possible to obtain a product that satisfies both sensitivity and reliability. be.

[Problem to be solved by the invention]

An object of the present invention is to provide a heat-sensitive recording material that improves the above-mentioned conventional drawbacks, that is, to provide a heat-sensitive recording material that is highly sensitive, has excellent reliability, and has excellent weather resistance.

[Means to solve the problem]

According to the present invention, in a heat-sensitive recording material in which a coloring layer containing a leuco dye and a color developer as main components is provided on a support, a basic calcium-based compound or a basic magnesium-based compound is used as a filler, and pH of the surface of the thermosensitive coloring layer
Provided is a heat-sensitive recording material characterized in that the number is 6 to 8.

The heat-sensitive recording material of the present invention uses a basic calcium-based compound or a basic magnesium-based compound as a filler in the color-forming layer and maintains the pH of the surface of the heat-sensitive color-forming layer at 6 to 8, so it has excellent weather resistance. Moreover, it can also be applied as a high-sensitivity recording material.

The filler used in the present invention is a basic calcium compound or a basic magnesium compound.

Examples of basic calcium compounds include calcium silicate and calcium carbonate, and examples of basic magnesium compounds include magnesium silicate, magnesium carbonate,
Examples include magnesium hydroxide and magnesium oxide.

Further, in the present invention, basic complexes such as a complex of magnesium carbonate and aluminum hydroxide, a complex of magnesium silicate and calcium silicate, a complex of magnesium hydroxide and calcium carbonate, and a complex of magnesium oxide and aluminum oxide are also used. Furthermore, it is also possible to use a form in which the above-mentioned compound or composite is coated on the surface of an inorganic material such as silica, zinc oxide, titanium oxide, etc. The use of these basic compounds or complexes can be determined as necessary to adjust the PL+ of the surface of the heat-sensitive coloring layer, but it is usually 50 to 60% by weight of the leuco dye for magnesium compounds, and 100 to 80% for calcium compounds.
0: tlt%, preferably 100 to 400 tlt% for magnesium compounds and 150 tlt% for calcium compounds.
~500wt-h1%. Another feature of the present invention is that the pH of the surface of the thermosensitive coloring layer is maintained at 6 to 8.

When the p++ of the surface of the heat-sensitive coloring layer is maintained at 6 to 8, the weather resistance of the heat-sensitive recording material is significantly improved.

The reason for this is not clear at present, but it is thought that the basic filler can suppress the coloring reaction between the dye and the acidic component in the base paper and the heat-sensitive coloring layer due to moisture in the air.

If it is outside the above range, weather resistance will be poor, and if the pH is less than 6, for example, skin fogging will occur, the skin will become black, and ρ
When 1 ( exceeds 8), a reaction with a phenolic compound occurs, which tends to cause yellowing.

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-chlorphthalide, 3.3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorfur Orane, 3-dimethylamino-5,7-dimethylfluorane.

3-diethylamine-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-
6-Methyl-7-chlorofluorane, 3-(N-p-tolyl-N-ethylamino)-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-trichloromethylanilino)fluoran, 3-diethylamino-7-(o- chloroanilino)fluoran, 3-dibutylamino-7-(0-chloroanilino)fluoran, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-he-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-pyrylosvirane, 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-47-chloro-5'
-methylphenyl)phthalide, 3-(N-ethyl-N-i-amyl)amino-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-tetrahydrofurfuryl)amino-6-methyl -7-anilinofluorane, 3-(N-
Ethyl-N=ethoxypropyl)amino-6-methyl-
7-anilinofluorane, 3-(N-methyl-N-isopropyl)amino-6-methyl-7-anilinofluorane, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(c-p-chlorphenyl) Methylaminofluorane, 3-diethylamino-5-chloro-7-(α-)edylethylamino)fluoran, 3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluoran, 3- Diethylamino-7-(0-methoxycarbonylphenylamino)fluoran.

3-diethylamino-5-methyl-7-(α-phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-
Chloro-3-(N-methyltoluidino)-7-(p-n
-butylanilino)fluorane, 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. sexual substance.

Examples include organic or inorganic acidic substances, esters and salts thereof, and the like.

gallic acid, salicylic acid, 3-isopropylsalicylic acid,
3-cyclohexylsalicylic acid, 3,5-di-tart
-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-tar
t-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-t
ert-octylcatechol, 2,2'-methylenebis(4-chlorophenol), 2,2'-methylenebis(
4-methyl-6-tart-butylphenol).

2.2'-dihydroxydiphenyl, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, p-
Butyl hydroxybenzoate, benzyl p-hydroxybenzoate, p-chlorobenzyl p-hydroxybenzoate, 0-chlorobenzyl p-hydroxybenzoate, p-
P-methylbenzyl hydroxybenzoate, n-octyl P-hydroxybenzoate, benzoic acid, zinc salicylate, ■-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-6-naphthoic acid Zinc, 4-hydroxydiphenylsulfone, 4-hydroxy-4'-chlorodiphenylsulfone, bis(4-hydroxyphenyl)sulfide, 2-hydroxy-P-toluic acid, zinc 3,5-di-tert-butylsalicylate, 3, Tin 5-di-tert-butylsalicylate, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, thiourea derivatives, 4-hydroxythiophenol derivatives, bis(
4-hydroxyphenyl)acetic acid, methyl bis(4-hydroxyphenyl)acetate, ethyl bis(4-hydroxyphenyl)acetate, bis(4-hydroxyphenyl)acetic acid n
-Propyl, bis(4-hydroxyphenyl)acetic acid n-
Butyl, bis(4-hydroxyphenyl)phenyl acetate, bis(4-hydroxyphenyl)benzyl acetate, bis(4-hydroxyphenyl)phenethyl acetate, bis(3-hydroxyphenyl)acetate,
-methyl-4-hydroxyphenyl)acetic acid, bis(3-
Methyl-4-hydroxyphenyl) methyl acetate, bis(
3-Methyl-4-hydroxyphenyl)ethyl acetate, bis(3-methyl-4-hydroxyphenyl)n-propyl acetate, 1,7-bis(4-hydroxyphenylthio)
3,5-dioxaheptane, 1,5-di(4-hydroxyphenylthio)-3-oxapentane, dimethyl 4-hydroxyphthalate, 4-hydroxy-41-methoxydiphenylsulfone, 4-hydroxy-4'- Ethoxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'-n
-Propoxydiphenylsulfone, 4-hydroxy-4
'-〇-Butoxydiphenylsulfone, 4-hydroxy-4'-isobutoxydiphenylsulfone, 4-hydroxy-4'-5ee-butoxydiphenylsulfone, 4
-hydroxy-4'-tar butoxydiphenylsulfone, 4-hydroxy-47-benzyloxydiphenylsulfone, 4-hydroxy-4'-phenoxydiphenylsulfone, 4-hydroxy-4'-(ffl-methylbenzyloxy)diphenylsulfone, 4-hydroxy-4
'-(p-methylbenzyloxy)diphenylsulfone,
4-hydroxy-4'-(o-methylbenzyloxy)diphenylsulfone, 4-hydroxy-4'-(ρ-chlorobenzyloxy)diphenylsulfone, and the like.

In the present invention, various conventional binders can be used as appropriate to bind and support the leuco dye and color developer on the support, such as polyvinyl alcohol, II! Powder and its derivatives, methoxycellulose, hydroxyethylcellulose.

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 In addition to water-soluble polymers such as alkali salts, inbutylene/maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic esters, Emulsions such as vinyl chloride/vinyl acetate copolymers, polybutyl methacrylate, ethylene/vinyl acetate copolymers, and latexes such as styrene/butadiene copolymers and styrene/butadiene/acrylic copolymers 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 surfactants, thermofusible substances (or lubricants), may be added. ) etc. can be used together. in this case,
Examples of thermofusible substances include higher fatty acids or their esters, amides, or metal salts, various waxes, condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, , 4-epoxy-hexahydrophthalate dialkyl, higher ketones, and other heat-fusible organic compounds having a melting point of about 50 to 200°C.

The heat-sensitive recording material of the present invention can be obtained, for example, by applying a coating liquid for forming a heat-sensitive layer containing the above-mentioned components onto a support such as paper, synthetic paper, or plastic film, drying it, and subjecting it to calender treatment. . In this case, it is also possible to provide an undercoat layer below the thermosensitive coloring layer and an overcoat layer above it. The amount of each used is 5 to 4 leuco dyes.
0% by weight, color developer 20-60% by weight, filler
) I requires adjustment, but 20 to 60% by weight and other auxiliary additives 30 to 60% by weight are appropriate.

〔Effect of the invention〕

The heat-sensitive recording material of the present invention has excellent weather resistance, hardly causing discoloration or fogging even if it is displayed on a wall for a long period of time, and is extremely practical.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples. Note that all parts and percentages shown below are based on weight.

Example 1 A mixture having the following composition was ground for 2 to 5 hours using a sand mill to prepare liquids (A) and (B), respectively.

[Liquid A]

3-Butylamino-6-methyl-7-20 parts Anilinofluorane 10% polyvinyl alcohol aqueous solution 20 parts Water
60 parts [Liquid B] Calcium carbonate 5 parts 1O%
Polyvinyl alcohol aqueous solution 25 parts water
50 copies Next, prepare a heat-sensitive coating liquid at a ratio of [Liquid A]: [Liquid B) = 1:8, and apply it to high-quality paper with a tsubo of 147 g/rrr so that the dry coating amount is 3.0 g/-. After drying, it was calendered to obtain a heat-sensitive recording paper of the present invention.

Example 2 The thermosensitive recording paper of the present invention was produced in the same manner as in Example 1 except that a composite of magnesium carbonate and aluminum hydroxide (Kyowa Kagaku Kiyo! Word 500) was used instead of silicon oxide coated with calcium carbonate. I got it.

Example 3 The thermal recording paper of the present invention was produced in the same manner as in Example 1 except that a compound containing calcium silicate as a main component (Fine Seal 5p-io manufactured by Tokuyama Soda) was used instead of silicon oxide coated with calcium carbonate. I got it.

Comparative Example 1 A comparative thermosensitive recording paper was obtained in the same manner as in Example 1, except that aluminum hydroxide (Hisilide 1 (-438) manufactured by Showa Light Metal) was used instead of the silicon oxide coated with calcium carbonate of Example 1.

Comparative Example 2 Silicon oxide (Mizusawa Chemical Industry [P-527)] was used instead of the silicon oxide coated with calcium carbonate of Example 1.
A comparative thermal recording paper was obtained in the same manner except that .

The following quality evaluations were carried out using the heat-sensitive recording paper of the present invention obtained as described above and the heat-sensitive recording paper for comparison.

(1) Dynamic coloring property: Head power 0.45W/
Dot, 17 A, / At 1a fJI20ms/Q,
Pulse width 0.2, 0.4.0.6.0.8.1, 0 m5ec under the condition of scanning line density 8 x 3.85 dots/mu
Macbeth Densitometer RD-914
It was measured with

(2) Paper surface pH: Measured using a paper surface inspection pH meter manufactured by Kyoritsu Rikagaku.

(3) Weather resistance: Posted on a wall indoors for 2 months, and the texture was visually judged.

0: There is almost no change or a slight discoloration of the solder. Δ: Discoloration is clearly observed, but it is at a level for practical use. As mentioned above, the heat-sensitive recording material of the present invention uses a specific filler and the surface pH of the heat-sensitive coloring layer is set to 6-8, so it has excellent color development compared to the comparative heat-sensitive recording paper. It can be seen that it also has excellent weather resistance.

Patent applicant Rico Co., Ltd.

Claims (1)

[Claims] (1) In a heat-sensitive recording material in which a color-forming layer containing a leuco dye and a color developer as main components is provided on a support, a basic calcium-based compound or a basic magnesium-based compound is used as a filler, and the heat-sensitive color-forming layer A heat-sensitive recording material characterized in that the pH of the surface thereof is set to 6 to 8.