JP2856093B2 - Thermal recording sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording sheet having excellent heat resistance, water resistance and oil resistance.

[0002]

2. Description of the Related Art Generally, a heat-sensitive recording sheet is prepared by grinding and dispersing a colorless or pale-colored basic colorless dye and an organic color developer such as a phenolic substance into fine particles, and then mixing and dispersing them together. A coating solution obtained by adding an agent, a sensitivity improver, a lubricant and other auxiliaries to a support such as paper, synthetic paper, film, plastic, etc. The color recording is obtained by an instantaneous chemical reaction caused by heating such as described above.

[0003] These thermosensitive recording sheets are used for measuring recorders, computer terminal printers, facsimile,
It has been applied to a wide range of fields such as automatic ticket vending machines and bar code labels, but recently, as these recording devices have been diversified and improved in performance, the required quality of thermal recording sheets has become higher. . For example, it is required that a high-density and vivid color image can be obtained even with a small amount of heat energy accompanying the high-speed recording, and on the other hand, light fastness,
There is a demand for a heat-sensitive recording sheet having excellent storability such as weather resistance and oil resistance.

As a conventional example of a heat-sensitive recording sheet, for example, Japanese Patent Publication No. 43-4160 or Japanese Patent Publication No. 45-1403
However, such a conventional heat-sensitive recording material has, for example, a low thermal response, and cannot provide a sufficient color density at the time of high-speed recording.

As a method for remedying such a defect, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran is used as a leuco dye (JP-A-49-109120). Dibutylamino-
Highly sensitive dyes such as those using 6-methyl-7-anilinofluoran (JP-A-59-190891) have been developed, and as a color developing agent, a substance having a good coloring property, 1,7-
Bis (4-hydroxyphenylthio) -3,5-dioxaheptane (JP-A-59-106456);
By using 5-bis (4-hydroxyphenylthio) -3-oxaheptane (JP-A-59-116262) and 4-hydroxy-4'-isopropoxydiphenylsulfone (JP-B-63-46067). Techniques for increasing the speed and increasing the sensitivity have been disclosed.

[0006]

However, although these heat-sensitive recording sheets have high sensitivity, they generally have a problem in heat resistance such that when stored at a high temperature, the image density is reduced.

Further, since the storage stability of the recorded image is remarkably poor, water or sebum components adhere to the color image, or come into contact with a plasticizer (DOP, DOA, etc.) contained in a wrap film such as a PVC film. As a result, disadvantages such as a remarkable decrease in image density and decoloration still remain.

An object of the present invention is to provide a heat-sensitive recording sheet having high sensitivity and excellent heat resistance, water resistance and oil resistance.

[0009]

According to the present invention, a dimerized thiourea compound represented by the following general formula (I) is contained in a thermosensitive coloring layer as an organic developer, and a basic colorless dye represented by the following formula (I): The above-mentioned problems have been solved all at once by including 3-n-dipentylamino-7- (m-trifluoromethylanilino) fluoran represented by II).

Embedded image (Wherein, X, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R
₇ and R ₈ are lower alkyl groups having 1 to 6 carbon atoms, 1 carbon atoms
To 6 alkoxy groups, hydrogen atoms, nitro groups, cyano groups,
Represents a halogen atom. m represents an integer of 1 to 3. )

Embedded image

In the present invention, the compound number and the structural formula of the dimerized thiourea compound used as an organic developer are exemplified, but the invention is not limited thereto.

[0011]

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The above dimerized thiourea compounds can be used alone or in combination of two or more as needed. In the present invention, other fluoran leuco dyes can be used in combination as long as the effects of the present invention are not impaired, and specific examples are shown below.

3-Diethylamino-6-methyl-7-anilinofluoran 3- (N-ethyl-p-toluidino) -6-methyl-
7-anilinofluoran 3- (N-ethyl-N-isoamylamino) -6-methyl-7-anilinofluoran 3-diethylamino-6-methyl-7- (o, p-dimethylanilino) fluoran 3 -Pyrrolidino-6-methyl-7-anilinofluoran 3-piperidino-6-methyl-7-anilinofluoran 3- (N-cyclohexyl-N-methylamino) -6
Methyl-7-anilinofluoran 3-diethylamino-7- (m-trifluoromethyl) -6-fluoran 3-N-n-dibutylamino-6-methyl-7-Anirinofuruora down 3 - (N-ethyl -N- Tetrahydrofurfurylamino) -6-methyl-7-anilinofluoran 3-dibutylamino-6-methyl-7- (o, p-dimethylanilino) fluoran 3- (N-methyl-N-propylamino)- 6-methyl-7-anilinofluoran 3-diethylamino-6-chloro-7-anilinofluoran 3-dibutylamino-7- (o-chloroanilino) fluoran 3-diethylamino-7- (o-chloroanilino) fluoran 3 -Diethylamino-6-methyl-chlorofluorane 3-diethylamino-6-methyl-fluoran 3-si Rohexylamino-6-chlorofluoran 3-diethylamino-benzo [a] -fluoran 3-n-dipentylamino-6-methyl-7-anilinofluoran 2- (4-oxo-hexyl) -3-dimethylamino −
6-methyl-7-anilinofluoran 2- (4-oxo-hexyl) -3-diethylamino-
6-methyl-7-anilinofluoran 2- (4-oxo-hexyl) -3-dipropylamino-6-methyl-7-anilinofluoran 3-diethylamino-6-methyl-7- (m-methylanilino ) Fluorane 3-dibutylamino-6-methyl-7- (m-methylanilino) fluoran

Further, as with the dyes, other color developers may be added to the organic color developer so as not to impair the effects of the present invention.

Further, as sensitizers, fatty acid amides such as stearic acid amide and palmitic acid amide, ethylene bisamide, montan wax, polyethylene wax, dibenzyl terephthalate, benzyl p-benzyloxybenzoate, di-p-tolyl carbonate , P-benzylbiphenyl, phenyl α-naphthyl carbonate, 1,4-diethoxynaphthalene, 1-hydroxy-
2-naphthoic acid phenyl ester, 1,2-di- (3-
Methylphenoxy) ethane, di (p-methylbenzyl) oxalate, β-benzyloxynaphthalene, 4-biphenyl p-tolyl ether and the like can also be added.

The binder used in the present invention is a completely saponified polyvinyl alcohol having a degree of polymerization of 200 to 1900, a partially saponified polyvinyl alcohol, a carboxy-modified polyvinyl alcohol, an amide-modified polyvinyl alcohol, a sulfonic acid-modified polyvinyl alcohol, a butyral-modified polyvinyl alcohol. Alcohol, other modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, styrene-maleic anhydride copolymer, styrene-butadiene copolymer and ethyl cellulose, cellulose derivatives such as acetyl cellulose, polyvinyl chloride, polyvinyl acetate,
Examples thereof include polyacrylamide, polyacrylate, polyvinyl butyral polystyrene, and copolymers thereof, polyamide resin, silicone resin, petroleum resin, terpene resin, ketone resin, and cumarone resin. These macromolecules are water, alcohol, ketone,
In addition to dissolving in solvents such as esters and hydrocarbons,
It is used in a state of being emulsified or dispersed in a paste form in water or another medium, and may be used in combination depending on required quality.

In the present invention, a known stabilizer metal salt of p-nitrobenzoic acid (Ca, Zn) or metal salt of monobenzyl phthalate (Ca, Zn) is used as long as the effects of the present invention are not impaired. It is also possible to add.

The filler used in the present invention includes silica,
Examples include inorganic or organic fillers such as calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, tanks, titanium oxide, and aluminum hydroxide.

In addition, a releasing agent such as a fatty acid metal salt, a lubricant such as a wax, a benzophenone-based or triazole-based ultraviolet absorber, a water-proofing agent such as glyoxal, a dispersant, and an antifoaming agent. Can be.

The amounts of the organic developer and the basic colorless dye used in the present invention and the types and amounts of other various components are determined according to the required performance and recording suitability, and are not particularly limited. Usually, for 1 part of the basic colorless dye, 1 to 8 parts of an organic color developer and 1 to 20 parts of a filler are used,
A suitable binder is 10 to 25% of the total solids.

The desired heat-sensitive recording sheet can be obtained by applying the coating solution having the above composition to any support such as paper, synthetic paper, film, plastic and the like.

Furthermore, an overcoat layer of a filler-containing polymer substance or the like can be provided on the thermosensitive coloring layer for the purpose of enhancing the storage stability.

Further, an undercoat layer containing an organic filler or an inorganic filler can be provided below the thermosensitive coloring layer for the purpose of enhancing the storage stability and sensitivity.

The above-mentioned organic color developer, basic colorless dye and optionally added materials are finely divided by a pulverizer such as a ball mill, an attritor, a sand grinder or an appropriate emulsifying device until the particle diameter becomes several microns or less. And a binder and various kinds of additive materials are added according to the purpose to obtain a coating liquid.

[0025]

The reason why the effects of the present invention can be obtained when a specific organic developer and a specific dye are combined in the present invention is considered as follows.

First, the excellent dynamic coloring ability is as follows.
This is because the melting and dispersing speed of the dye and the saturation solubility of the dye with respect to the developer of the present invention are large, and a recorded image can be formed instantaneously by instantaneous contact of a high-heat thermal head.

The reason why the recorded image has extremely high stability in terms of water resistance and oil resistance is explained as follows. In general, a thermosensitive recording paper is constituted by using a basic colorless dye as an electron donor and an organic acidic substance such as a phenol compound, an aromatic carboxylic acid or an organic sulfonic acid as an electron acceptor. The heat-melting reaction between these basic colorless dyes and the developer is a
This is an acid-base reaction based on acceptance, whereby a metastable “charge transfer complex” is formed, and a color image is obtained.

In the case where the specific dimerized thiourea compound of the present invention is used as an organic color developer, the coloration process between the dimerized thiourea compound and a specific fluoran leuco dye which is a basic colorless dye is carried out. Has a chemical bonding force other than that of the present invention (for example, benzyl 4-hydroxybenzoate,
4-hydroxy-4'-isopropoxydiphenylsulfone, 4,4'-isopropylidenediphenol) and fluoran leuco dyes are specifically stronger than the chemical bonding force. Even when exposed for a long time under the environmental conditions, the chemical bond is not broken and the stability of the color image is maintained.

[0029]

The present invention will be described below with reference to examples and comparative examples. In addition, in description, a part shows a weight part. Example 1 (Test Nos. 1 to 20) Solution A (dye dispersion) Dye 3-n-dipentylamino-7- (m-trifluoromethylanilino) fluoran 2.0 parts 10% aqueous solution of polyvinyl alcohol 4 6.6 parts water 2.5 parts liquid B (developer dispersion liquid) dimerized thiourea compound (see Table 1) 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts water 11.2 parts of the above composition Each liquid was ground with a sand grinder to a particle size of 1 micron. Next, the dispersion liquid is mixed at the following ratio to obtain a coating liquid. Liquid A (dye dispersion) 9.1 parts Liquid B (developer dispersion) 36.0 parts Kaolin clay (50% dispersion) 12.0 parts One side of each of the above coating liquids at 50 g / m ² of base paper 5.0 coating amount
g / m ² and dried, and this sheet was treated with a super calender so that the smoothness became 400 to 500 seconds to obtain a thermosensitive recording paper having black coloring.

Comparative Example 1 (Test Nos. 21 to 25)
A thermosensitive recording paper was obtained in the same manner as in Example 1, except that the dye of the solution A was replaced with the dye shown in Table 3.

[Comparative Example 2 (Test Nos. 26 to 30)] Solution C (dye dispersion) Dye (see Table 3) 2.0 parts 10% aqueous polyvinyl alcohol solution 4.6 parts Water 2.5 parts Solution D ( Developer dispersion) Developer (see Table 3) 6.0 parts 10% aqueous polyvinyl alcohol solution 18.8 parts Water 11.2 parts Each liquid of the above composition is ground to a particle size of 1 micron with a sand grinder. did. Next, the dispersion liquid is mixed at the following ratio to obtain a coating liquid. Liquid C (dye dispersion) 9.1 parts Liquid D (developing agent dispersion) 36.0 parts Kaolin clay (50% dispersion) 12.0 parts One side of each of the above coating liquids at 50 g / m ^{2 on} a base paper 5.0 coating amount
g / m ² and dried, and this sheet was treated with a super calender to have a smoothness of 400 to 500 seconds to obtain a thermosensitive recording paper.

The thermal recording papers obtained in the above Examples and Comparative Examples were subjected to the following quality performance tests, and the results are shown in Tables 2 and 4.

However, leuco dye A in Tables 1 and 3
B, C, D, E and F represent the following compounds, respectively.

A: 3-n-dipentylamino-7- (m
-Trifluoromethylanilino) fluoran B; 3-diethylamino-7- (m-trifluoromethylanilino) fluoran C; 3- (N-cyclohexyl-N-methylamino)-
6-methyl-7-anilinofluoran D; 3-n-dibutylamino-6-methyl-7-anilinofluoran E; 3-n-dipentylamino-6-methyl-7-anilinofluoran F; 3- (N-ethyl-N-isoamylamino) -6
Methyl-7-anilinofluoran injection (1) Dynamic color density; manufactured by Tokyo Shibaura Electric Co., Ltd.-Thermal facsimile KB-4800
And an image density recorded with an applied voltage of 18.03 V and a pulse width of 3.2 milliseconds using a Macbeth densitometer (RD-91
4, Use of amber filter. same as below. ) Measured. Note (2) Heat resistance: The image density of a thermal paper sample dynamically recorded by the method of Note (1) was measured with a Macbeth densitometer after being left for 24 hours under a high-temperature drying condition of 60 ° C. The residual rate is calculated from the following equation.

(Equation 1) Note (3) Water resistance: A thermal paper sample dynamically recorded by the method of Note (1) was immersed in cold water at 20 ° C. for 24 hours, dried, and the recorded portion was measured with a Macbeth densitometer. The residual rate is calculated from the following equation.

(Equation 2) Note (4) Oil resistance; manufactured by Tokyo Shibaura Electric-Thermal facsimile K
Using a B-4800, an image density recorded at an applied voltage of 18.03 V and a pulse width of 3.2 milliseconds was measured by a Macbeth densitometer (using an RD-914 amber filter) to obtain an unprocessed density. Then, salad oil is dripped onto the print coloring portion, and after 10 seconds, it is lightly wiped with a filter paper.
After standing for a while, the image density was measured with a Macbeth densitometer. The residual rate is calculated from the following equation.

(Equation 3)

[0035]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[0036]

(1) Because of its excellent thermal response, a clear high-density image can be obtained even at high speed and high density recording. (High sensitivity) (2) The printed portion (colored portion) hardly loses color even when it comes into contact with a plasticizer, salad oil, vinegar or the like. (Oil resistance) (3) The printed portion hardly loses color even when it comes into contact with water. (Water resistance) (4) The image is stable even under high temperature conditions. (Heat-resistant)

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41M 5/28-5/34 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A thermosensitive recording sheet comprising a support having thereon a thermosensitive coloring layer containing a colorless or pale-colored basic colorless dye and an organic developer as main components, wherein said thermosensitive coloring layer comprises an organic developer. A heat-sensitive recording sheet comprising a dimerized thiourea compound represented by the following general formula (I) and a fluoran leuco dye represented by the following formula (II) as a basic colorless dye. Embedded image (Wherein, X, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R
₇ and R ₈ are lower alkyl groups having 1 to 6 carbon atoms, 1 carbon atoms
To 6 alkoxy groups, hydrogen atoms, nitro groups, cyano groups,
Represents a halogen atom. m represents an integer of 1 to 3. )