JPS5834310B2 - thermal recording paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-sensitive recording paper, and more particularly to a heat-sensitive recording paper having excellent heat resistance, water resistance, etc., and improved heat-sensitive characteristics.

The minimum performance required for a recording layer of thermal recording paper is excellent self-coloring resistance, pressure coloring resistance, heat sensitivity, light resistance, heat decoloring resistance, moisture decoloring resistance, and water resistance. However, we have not yet obtained anything that completely satisfies these requirements.

First, as a method of improving self-coloring resistance,
8-101943 (Japanese Patent Publication No. 51-29830) describes the addition of a water-soluble alkanolamine compound, and JP-A-49-11141 (Japanese Patent Publication No. 51-2823) describes the addition of a basic organic compound. ing.

Methods for improving water resistance include JP-A-493643, JP-A-49-32646, and JP-A-50-30539.
No., JP-A-52-145228 and JP-A-53-1
No. 3929 and the like describes the use of a water-soluble binder and a water-resistant agent in combination.

As a method for improving colorfastness, Japanese Patent Application Laid-Open No. 48-52
In JP-A No. 49-45747 (Japanese Patent Publication No. 51-43386), 4,41-thiobis(6
JP-A No. 53-17347 describes the addition of water-insoluble modified phenol resins such as rosin-modified or terpene-modified resins. ing.

In addition, as a method for improving heat-sensitive characteristics,
7748 and Japanese Patent Publication No. 51-39567, the use of an organic acid and a phenolic compound as acidic substances in combination;
Alternatively, it is described that a polyvalent metal salt of a compound having an alcoholic hydroxyl group is used.

JP-A No. 49-11140 (Japanese Patent Publication No. 51-29945) describes the use of a copolymer of hydroxyethyl cellulose and maleic anhydride.

Furthermore, JP-A-49-34842, JP-A-49-11
No. 5554, JP-A-50149353, JP-A-52-
No. 106746, JP-A-53-5636, JP-A-53
-11036 and JP-A No. 53-48751, etc. contain compounds such as thioacetanilide, phthalonitrile, acetamide, di-β-naphthyl-p-phenylenediamine, fatty acid amide, acetoacetanilide, diphenylamine, penzamide, carbazole, etc. Nitrogen organic compounds or thermofusible substances such as 2,3-di-m-tolylbutane, 4,4'-dimethylbiphenyl, etc., or carboxylic acid esters such as dimethyl isotucrate, diphenyl phthalate, etc. are used as sensitizers. It is described that it can be added as

The present inventors manufactured thermal recording paper using a known fluoran compound as a coloring agent and according to the methods described in the above-mentioned patent publications and the methods described in the above-mentioned patent publications. When tested on the surface,
The heat-sensitive properties were poor, such as a high initial color development temperature (Ts) upon heating, a small rising temperature coefficient (r) of a color density curve, and a low maximum color density (Dmax).

For this reason, it is not practical as a thermal recording paper for facsimile 1, especially high-speed facsimile.

In addition, thermally colored recording paper was heated at 50 to 60°C, relative humidity 2
When the sample was left in a 0% atmosphere for 3 to 5 days, the concentration of the color former was lower than that immediately after the color development.

That is, heat decolorization resistance is low. Furthermore, if left in an atmosphere of 50 to 60°C and relative humidity of 80 to 90% for 12 to 24 hours, the concentration of the color former will decrease compared to the color concentration immediately after color development, and in some cases it will disappear completely. Even traces of the coloring agent that caused the color to develop are no longer visible.

In other words, the moisture decoloring resistance is low.

When thermal recording paper that uses a water-soluble binder as a binder or thermal recording paper that has been colored by heating is immersed in water for a long time, both the uncolored thermal recording layer and the colored thermal recording layer will flow. , or faded.

In other words, water resistance is poor. The present inventors completed the present invention as a result of intensive research in order to improve the above-mentioned drawbacks of heat-sensitive recording paper using known fluoran compounds.

That is, the present invention provides a heat-sensitive recording paper comprising, on a support, a recording layer basically comprising a colorless or slightly pale fluoran compound, an acidic substance that causes the fluoran compound to develop color when heated, and a binder. , 40'C in the recording layer
A general formula having a melting point of , n is an integer of 1 to 4, and R1 and R2 are not hydrogen atoms at the same time.

) is a thermosensitive recording paper characterized by containing one or more kinds of terephucuric acid ester compounds.

The normally colorless or light-colored fluoran compound used in the thermal recording paper of the present invention can be selected from a large number of conventionally known fluoran compounds. Formula (in the formula, R3 is a lower alkyl group, R4 is a lower alkyl group, a cyclohexyl group, or an optionally substituted phenyl group, and R3 and R4 may form a heterocycle together with the nitrogen atom to which they are bonded) , X is a hydrogen atom or a lower alkyl group, Y is a hydrogen atom, a lower alkyl group,
It is a halogen atom or a trifluoromethyl group.

) is a conventionally known compound represented by

The representative compounds are listed as follows: 2-(chloroanilino)-6-ethylaminofluorane, 2-anilino-3-methyl-6-dinithylaminofluorane, 2-anilino-3-methyl-6-pyrroli. Dinylfluorane, 2-72lJ no 3-methyl-6-piperidinofluorane, 2(3-trifluoromethylanilino)-6-dinithylaminofluorane, 2-anilino-6
-Dinithylaminofluorane, 2-anilino-3-methyl-6-(N-ethyl-N-p-1-lyl)aminofluorane, 2-(p-ethoxyanilino)-3-methyl-
6-diethylaminofluorane, 2-xylidino-3-
Examples include methyl-6-diethylaminofluoran, 2-anilino-3-methyl-6-(N-methyl-N-cyclohexylamino)fluoran, but the fluoran compound is not limited to these fluoran compounds.

The acidic substance used in the present invention is a substance that is solid at room temperature and can react with a color forming agent when heated. Typical examples include phenolic compounds or stearic acid described in Japanese Patent Publication No. 14039/1983. , benzoic acid, gallic acid, salicylic acid, etc., which have the property of liquefying or vaporizing at 50° C. or higher, or their metal salts such as aluminum and zinc.

Acidic substances that can be suitably used are the above-mentioned phenolic compounds, a typical example of which is 4,4'-isopropylidenediphenol (bisphesol A) compound.

Next, typical examples of the terephthalic acid ester compound represented by general gI according to the present invention will be listed, but these representative examples are not intended to limit the present invention.

Terephthalic acid dimethyl ester, terephthalic acid diethyl ester, terephthalic acid monoethyl ester, terephthalic acid diisopropyl ester, terephthalic acid monopropyl ester, terephthalic acid monopropyl ester, terephthalic acid diptyl ester, terephthalic acid monobutyl ester, terephthalic acid dit -butyl ester, terephthalic acid monooctyl ester, terephthalic acid-bis(3,5,5-trimethylhexyl) ester, 2-methoxy-terephthalic acid dimethyl ester, 2-methyl-terephthalic acid dimethyl ester, 2-chloro-terephthalic acid dimethyl ester Examples include ester, 2,5-dichloro-terephthalic acid dimethyl ester, 2-chloro-5-bromo-terephthalic acid diethyl ester, tetrachloroterephthalic acid dimethyl ester, terephthalic acid diphenyl ester.

A water-soluble or water-insoluble binder is used as a binder for binding a mixture of a color former, an acidic substance, and a terephthalic acid ester compound (hereinafter referred to as an additive compound) onto a support sheet.

Typical examples include polyvinyl alcohol, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, gum arabic, starch, gelatin, casein, polyvinylpyrrolidone, styrene-maleic anhydride copolymer, polyacrylic acid amide, polyacrylate, Although there are terpene resins and petroleum resins, binders that can be particularly preferably used in the present invention are water-soluble binders,
A typical example is polyvinyl alcohol.

To produce the thermal recording paper of the present invention, each component consisting of a fluoran compound as a coloring agent, an acidic substance, and one or more terephthalic acid ester compounds represented by the general formula [I] is formed into fine particles. A method in which the particles are present in a uniform state in one heat-sensitive layer is preferable from the viewpoint of the performance of the heat-sensitive recording paper.

Alternatively, each component consisting of a coloring agent and an additive compound exists in a uniform state as fine particles in one layer, and a layer in which fine particles of an acidic substance exist in a uniform state by adhering to this layer. A method in which each component consisting of an acidic substance and an additive compound is present as fine particles in a uniform state in one layer, and the fine particles of the coloring agent are brought into close contact with this layer in a uniform state. The method of providing the existing layer, furthermore, the color former, additive compound and acidic substance as fine particles,
There is a method in which layers existing in a uniform state among separate layers are brought into close contact with each other.

When producing the heat-sensitive recording paper of the present invention, the weight ratio of each of the above-mentioned components and binder in the recording layer to the coloring agent is 0.0.
1 to 3 times, preferably 0.3 to 1 times, acidic substances 2 to 10 times, preferably 4 to 6 times, and binders 0.3 to 1 times.
It is 3 to 3 times, preferably 0.5 to 1 times.

The color former, acidic substance and additive compound are preferably each separately dispersed in a dispersing machine such as a ball mill, sand mill or paint conditioner in water or an organic medium containing a binder, preferably in which the binder is dissolved. Disperse using water as a medium and crush to 1 to 6μ, preferably 3
Make a suspension with a particle size of ~5μ.

If necessary, an antifoaming agent, dispersant, or brightener may be added for dispersion and pulverization.

Next, a suspension of each of the separately dispersed and pulverized components described above is mixed so that the weight ratio of each component in the recording layer is as described above to prepare a paint for forming a heat-sensitive recording layer.

Apply this paint to the surface of the paper using wire par +6 to #10.
A heat-sensitive recording paper is produced by applying the coating so that the weight of the solid after drying is 3 to 7D, and drying it in a blow dryer at room temperature to 70°C.

If necessary, inorganic or organic fillers may be added to the paint to improve the fusing resistance, writability, etc. of the thermal head.

The heat-sensitive recording paper of the present invention obtained in this way has excellent heat-sensitive properties, heat decolorization resistance, moisture decolorization resistance, and water resistance, and can effectively overcome the drawbacks of conventionally known thermal recording papers. there were.

The performance of the recording layer of the thermosensitive recording paper was tested using the following test method.

In other words, the color density of the self-developed color, the color density after heat color development at each temperature, and the decolorization density of the color former in hot air or humidity after heat color development is measured using a Macbeth RD-514 reflection densitometer. Measured using

The heating temperature was 80 to 170℃ using a Rhodiaceta type thermotest tester (manufactured by the French National Textile Research Institute).
The heating time was 3 seconds and the load was 101/-.

Further, decoloring of the coloring agent after coloring by heating was carried out using a constant temperature and humidity tester.

The present invention will be specifically explained below using examples, but the present invention is not limited to these examples.

Example 1 (1) 40 g of 2-(2-chloroanilino)-6-dinithylaminofluoran aqueous solution of 4, 9, 10% by weight polyvinyl algol was dispersed in a ball mill for 48 hours and pulverized to obtain suspension particles with a particle size of 2 to 3μ. A cloudy liquid (A) was obtained.

Next, 40 g of a 10% by weight polyvinyl alcohol aqueous solution of bisphenol A 7,91 and 10 g of water were dispersed in a ball mill for 48 hours and pulverized to form a suspension with a particle size of 2 to 3 μm (liquid B).
I got it.

Furthermore, 7 g of dimethyl terephthalate, 40.9 g of a 10% by weight aqueous polyvinyl alcohol solution, and 10 g of water were dispersed in a ball mill for 48 hours and ground to form a suspension with a particle size of 2 to 3 μm (
Solution C) was obtained.

A heat-sensitive paint was obtained by mixing liquids A, B, and C at a weight ratio of 3:10:3.

This paint was applied to the surface of high-quality paper using a #10 wire bar so that the solid content weight after drying would be 5 Vm, and the paint was placed in a blow dryer and dried at room temperature to form the thermal recording paper (A) of the present invention. I got it.

(2) Diethyl terephthalate 75', 40 g of a 10% by weight aqueous polyvinyl alcohol solution, and 10 g of water were dispersed for 48 hours in a ball mill and pulverized to form a suspension with a particle size of 2 to 3 μm (D
) liquid was obtained.

Liquids A, B, and D from (1) above were mixed at a weight ratio of 3:10:3 to obtain a thermal paint.

Apply this paint to the surface of high-quality paper using a +10 wire bar so that the solid content after drying is 5.
The thermal recording paper of the present invention (
b) was obtained.

(3) 7 g of isopropyl terephthalate, 40.9 g of a 10% by weight aqueous polyvinyl alcohol solution and 10 g of water were dispersed in a ball mill for 48 hours and pulverized to obtain a suspension (E) with a particle size of 2 to 3 μm.

Liquids A, B, and E in (1) above are mixed at a weight ratio of 3:10:3 to obtain a heat-sensitive paint, which is coated on high-quality paper in the same manner as in (1) above. c) was obtained.

(4) Mix liquid A and liquid B from (1) above at a weight ratio of 3:10 to obtain thermal paint 2, and obtain control thermal recording paper (d) in the same manner as in (1) above. Ta.

(5) 7 g of dimethyl isophthalate, 40.9 g of a 10 wt.
liquid) was obtained.

The A, B, and F solutions in (1) above were mixed at a weight ratio of 3:10:3 to obtain a thermal paint, and a control thermal recording paper (E) was obtained in the same manner as in (1) above. Ta.

(6) Diphenyl phthalate 79, 40 g of a 10% by weight polyvinyl alcohol aqueous solution and 10 g of water were dispersed in a ball mill for 48 hours and ground to form a suspension with a particle size of 2 to 3 μm (Liquid G).
I got it.

The above (1) liquids A, B, and G were mixed at a weight ratio of 3:10:3 to obtain a thermal paint, and a control thermal recording paper was obtained in the same manner as in (1) above. Ta.

The performance of the recording layer of the produced thermal papers (a) to (f) was tested by the method described above, and the results are shown in the attached table.

Example 2 (1) 4 g of 2-anilino-3-methyl-6-dinithylaminofluorane and 40 g of a 10% by weight polyvinyl alcohol aqueous solution were dispersed in a ball mill for 48 hours and pulverized to obtain a particle size of 2.
A suspension (H) of ~3μ was obtained.

Solution H and solution B and solution C of Example 1-(1) above were mixed in a ratio of 3:10:
A thermosensitive recording paper (G) was obtained in the same manner as in Example 1.

(2) Mix the H liquid from (1) above and the B liquid from Example 1-(1) at a weight ratio of 3:10, and obtain a control thermal recording paper (H) in the same manner as in Example 1. Ta.

The performance of the recording layer of the heat-sensitive recording papers (G) and (H) produced above was tested by the method described above, and the results are shown in the attached table.

Example 3 (1) 40 g of 2-anilino-3-methyl-6-pyrrolidinyl fluorane 4,9,10% by weight polyvinyl alcohol aqueous solution was dispersed in a ball mill for 48 hours and pulverized to obtain a particle size of 2.
A suspension (J) of ~3μ was obtained.

Solution J and solution B and solution C of Example 1-(1) above were mixed at 3=10:
A thermosensitive recording paper was obtained in the same manner as in Example 1.

(2) Mix liquid J from (1) above and liquid B from Example 1-(1) at a weight ratio of 3:10, and obtain a control thermal recording paper (nu) in the same manner as in Example 1. Ta.

The performance of the recording layer of the heat-sensitive recording papers (S) and (N) produced above was tested by the method described above, and the results are shown in the attached table.

Claims (1)

[Scope of Claims] 1. A thermal recording comprising a recording layer provided on a support, which basically includes a colorless or slightly pale fluoran compound, an acidic substance that causes the fluoran compound to develop color when heated, and a binder. In paper, the recording layer has a general formula (wherein R1 and R2 are a hydrogen atom, an alkyl group having 1 to 9 carbon atoms, or an optionally substituted phenyl group, and R3 is hydrogen atom, lower alkyl group, alkoxy group, or halogen atom, n is an integer of 1 to 4, and R1 and R2 are not hydrogen atoms at the same time.) Contains one or more terephthalic acid ester compounds represented by A thermal recording paper characterized by: