JP2003103939A - Developer and heat sensitive recording material including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording material, which has a high color developing sensitivity and an excellent storage stability of ground. SOLUTION: In order to obtain the heat sensitive recording material having a heat sensitive color developing layer including a developer and a color developing dye on a support, a dispersant liquid is coated on the support and then dried after the dispersant liquid is prepared by dispersing the developer mainly made of a 2,4'-dihydroxydiphenylsulfone having 0.1 wt.% or less of a trihydroxytriphenyldisulfone as its impurity and the color developing dye in a dispersion medium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color developer and a heat-sensitive recording material containing the same, and more specifically, to a color developer containing 2,4'-dihydroxydiphenyl sulfone as a main component and the same. The present invention relates to a thermosensitive recording material.

[0002]

2. Description of the Related Art Conventionally, a thermosensitive recording paper (thermosensitive recording material) having a thermosensitive coloring layer containing a color developer and a coloring dye is represented by an information communication device such as a facsimile and an information recording device such as a printer. Widely used as recording paper (output paper) for various devices. The thermosensitive recording paper has high color development sensitivity (color development) and high fastness of a color image and background (a part where no color image is not formed) so that it can be stored for a long period of time (small change with time). ) And other physical properties are required.

By the way, as the developer, a developer containing 2,4'-dihydroxydiphenyl sulfone as a main component is widely used. And, conventionally, 2,4 '
-Various proposals have been made as a method for improving various physical properties of dihydroxydiphenyl sulfone desired as a color developer. For example, Japanese Patent No. 2116148 and Japanese Patent No. 2745172 disclose a method of improving color development sensitivity and storage stability of a thermal recording material containing 2,4′-dihydroxydiphenyl sulfone.

[0004]

However, the heat-sensitive recording paper currently on the market has a large change over time, such as the color image becoming difficult to see due to the discoloration of the background after long-term storage. That is, the heat-sensitive recording paper currently on the market has a problem that it is not possible to sufficiently satisfy the various physical properties required for the heat-sensitive recording paper. Therefore, there is a demand for a heat-sensitive recording material having high color development sensitivity and excellent storage stability of the background.

Further, when 2,4'-dihydroxydiphenyl sulfone improved by the above-mentioned conventional method is used as a color developing agent for a heat sensitive recording paper, although a certain degree of improvement in color developing sensitivity is recognized, the color developing sensitivity is improved for a long period of time. The storage stability over time, especially the heat resistance and moist heat resistance of the background are still poor. That is, none of the above-mentioned conventional methods can improve the storage stability of the thermosensitive recording paper to a sufficiently satisfactory level. Therefore, there is a need for 2,4′-dihydroxydiphenyl sulfone, which is suitable for producing a heat-sensitive recording paper that is particularly excellent in the storage stability of the background.

The present invention has been made in view of the above problems of the prior art, and its main object is to provide a heat-sensitive recording material having high color-developing sensitivity and excellent storage stability of the background.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the amount of trihydroxytriphenyldisulfone, which is an impurity contained in 2,4′-dihydroxydiphenylsulfone, and the amount of 2 Although the mechanism (causal relationship) with various physical properties of the color developer containing 4,4'-dihydroxydiphenyl sulfone as a main component is not clear, it was found that there is a correlation. Based on the findings that have not been known at all, the content of trihydroxytriphenyldisulfone is 0.1
It was confirmed that a heat-sensitive recording material using a color developer containing 2,4′-dihydroxydiphenyl sulfone as a main component in an amount of less than or equal to wt% has high color development sensitivity and excellent background storage stability. The present invention has been completed.

That is, in order to solve the above problems, the color developer of the present invention contains trihydroxytriphenyldisulfone as an impurity in an amount of 0.1% by weight or less.
It is characterized by containing 4'-dihydroxydiphenyl sulfone as a main component.

According to the above constitution, it is possible to provide a color developer suitable for obtaining a heat-sensitive recording material having high color development sensitivity and excellent storage stability of the background.

In order to solve the above-mentioned problems, the dispersion of the present invention is characterized in that the above-mentioned color developer and color-forming dye are dispersed in a dispersion medium. Therefore, it is possible to provide a dispersion liquid containing a color developer suitable for obtaining a heat-sensitive recording material having high color development sensitivity and excellent storage stability of the background.

In order to solve the above problems, the heat-sensitive recording material of the present invention is a heat-sensitive recording material having a heat-sensitive color-forming layer containing a color-developing agent and a color-forming dye on a support. However, the content of 2,4′-dihydroxydiphenylsulfone containing 0.1% by weight or less of trihydroxytriphenyldisulfone as an impurity is a main component.

According to the above constitution, the color developer contains 2,4'-dihydroxydiphenylsulfone as a main component, in which the content of trihydroxytriphenyldisulfone as an impurity is 0.1% by weight or less. . This allows
It is possible to provide a thermosensitive recording material having high color development sensitivity and excellent storage stability of the background.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The following will describe one embodiment of the present invention.

The heat-sensitive recording material according to the present invention has a heat-sensitive color-forming layer containing a color-developing agent and a color-developing dye on a support, and the color-developing agent contains trihydroxytriphenyldisulfone "HO-" which is an impurity. _{C 6 H 4 -SO 2 -C 6} H 3 (OH) -S
O ₂ -C ₆ H ₄ -OH content (so-called tri-form) "is 0.1 wt% or less of 2,4'-dihydroxydiphenyl sulfone" _{HO-C 6 H 4 -SO 2} -C 6 H 4 -O
H (2,4′-bisphenol S) ”is contained as a main component.

In the present invention, the "content of trihydroxytriphenyldisulfone which is an impurity" means the content calculated from the area of trihydroxytriphenyldisulfone on the chart of liquid chromatography. The measuring method (measuring conditions) of liquid chromatography is as follows. That is, the column: YMC ODS-A
300mm × 6φ, mobile phase: 0.05M-KH ₂ PO
₄ / CH ₃ CN = 70/30, flow rate: 1.0 ml / min,
The detection wavelength is 254 nm, and the retention time of trihydroxytriphenyldisulfone under this condition is about 20 minutes.

The 2,4'-dihydroxydiphenyl sulfone according to the present invention can be obtained, for example, by a dehydration reaction of phenol with p-phenolsulfonic acid and / or o-phenolsulfonic acid or a dehydration reaction of phenol with sulfuric acid. It can be manufactured at low cost. The 2,4'-dihydroxydiphenyl sulfone thus obtained is then subjected to various ordinary purification operations such as crystallization, filtration, decolorization and recrystallization as appropriate to obtain impurities in the 2,4'-dihydroxydiphenyl sulfone. The content of trihydroxytriphenyldisulfone contained as can be adjusted to 0.1% by weight or less. Therefore, the 2,4′-dihydroxydiphenyl sulfone according to the present invention may be adjusted so that the content of trihydroxytriphenyldisulfone is adjusted to 0.1% by weight or less, and the production method thereof is not particularly limited. Absent.

When a developer containing 2,4'-dihydroxydiphenylsulfone as a main component in which the content of trihydroxytriphenyldisulfone exceeds 0.1% by weight is used, the background of the heat-sensitive recording material (a colored image is formed). The storage stability of the part (not shown) is significantly reduced.

When producing 2,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfone is produced in addition to trihydroxytriphenyldisulfone and the like. However, 4,4′-dihydroxydiphenyl sulfone may be contained in 2,4′-dihydroxydiphenyl sulfone as long as various physical properties desired for the heat-sensitive recording material are not impaired.

As a result, 2,4 'which is suitable as a color developer
-Dihydroxydiphenyl sulfone is obtained. That is,
It is possible to obtain 2,4′-dihydroxydiphenyl sulfone suitable for obtaining a heat-sensitive recording material having high color development sensitivity and excellent storage stability of the background.

Then, a dispersion prepared by dispersing the above-mentioned color developer containing 2,4'-dihydroxydiphenyl sulfone as a main component and a color forming dye in a dispersion medium is coated on a support and dried. Thereby, the thermosensitive coloring layer can be formed. That is, it is possible to produce a thermosensitive recording material having a thermosensitive coloring layer containing a color developer and a coloring dye on a support.

Specific examples of the color forming dye include 7'-anilino-3 '-(dibutylamino) -6'.
-Methylfluorane "3-di-n-butylamino-6-
Methyl-7-anilinofluoran ", 7'-anilino-
3 '-(dipentylamino) -6'-methylfluorane, 3,3-bis (p-dimethylaminophenyl) -6
-Dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3- (2-phenyl-3-indolyl) phthalide, 3- (p-dimethylaminophenyl) -3-
(1,2-Dimethyl-3-indolyl) phthalide, 3,
3-bis (9-ethyl-3-carbazolyl) -5-dimethylaminophthalide, 3,3-bis (2-phenyl-3)
-Indolyl) -5-dimethylaminophthalide and other triarylmethane dyes (phthalide dye, triphenylmethane dye); 4,4'-bisdimethylaminobenzhydridobenzyl ether and other diphenylmethane dyes; benzoyl leuco methylene blue And other thiazine dyes (phenothiazine dyes); 3-methylspirodinaphthopyran and other spiro dyes (spiropyran dyes); lactam dyes; fluorane dyes; leuco auramine dyes; indoline dyes; indigo dyes And the like, but it is not particularly limited as long as it is a colorless or pale color at normal temperature and can develop a color by reacting with a developer which is an acidic substance when heated. Not a thing. These color forming dyes may be used alone or in combination of two or more.

In the present invention, 2,4 'in the color developer
The proportion of -dihydroxydiphenyl sulfone is particularly preferably 95% by weight or more. 2, in the developer
Specific examples of components (compounds) other than 4′-dihydroxydiphenyl sulfone include p-octylphenol, pt-butylphenol, p-phenylphenol, p-hydroxyacetophenone, α-naphthol, and p-tertiary. Octylcatechol, 2,2'-dihydroxybiphenyl, 1,1-bis (p-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (3-methyl-4-hydroxy) Phenyl) propane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane, 2,2-bis (3,5-dichloro-4-hydroxyphenyl) propane, bis (3-allyl-4-) Hydroxyphenyl) sulfone, bis (3,4-dihydroxyphenyl) sulfone, 1,1-bis (4- Hydroxyphenyl) cyclohexane, bis (4-hydroxyphenylether) bis {2- (4-hydroxyphenylthio) ethoxy} methane, 4- (4-isopropoxybenzenesulfonyl) phenol, dimethyl 4-hydroxyphthalate, bis (4
-Hydroxyphenyl) butyl acetate, benzyl p-hydroxybenzoate, 3,5-di-t-butylsalicylic acid and other phenols; benzoic acid, phthalic acid, salicylic acid and other aromatic carboxylic acids; zinc salicylate and other aromatic carboxylic acids Acid metal salts; and the like, as long as they are compounds capable of reacting with a color forming dye when heated,
It is not particularly limited. These compounds may be used alone or in combination of two or more, as required.

The amount of the color-developing agent used with respect to the color-developing dye may be set according to the type and combination of the color-developing dye and the color-developing agent, and is not particularly limited, but 1 part by weight of the color-developing dye is used. On the other hand, the range of 1 to 6 parts by weight of the color developer is more preferable, and the range of 1.5 to 2.5 parts by weight is further preferable.

The dispersion medium is not particularly limited as long as it is a compound that can disperse the color developer and the color-forming dye, but a so-called water-soluble binder such as water or polyvinyl alcohol is preferable. .

The dispersion may further contain a sensitizer, if necessary. That is, the thermosensitive color-forming layer formed using the dispersion liquid further contains a sensitizer, if necessary, in order to further improve the color-forming sensitivity, as long as it does not impair various physical properties desired for the thermosensitive recording material. You may stay. As the sensitizer, a compound having a melting point in the range of 50 to 150 ° C. is preferable, and specific examples thereof include nitrogen-containing compounds such as stearic acid amide, palmitic acid amide, linoleic acid amide, and stearic acid anilide. Compounds: 4-hydroxybenzoic acid benzyl ester, 4-benzyloxybenzoic acid benzyl ester, 2-naphthoic acid phenyl ester, 2-naphthoic acid benzyl ester, 1-hydroxy-2-naphthoic acid phenyl ester, oxalic acid dibenzyl ester, Ester compounds such as oxalic acid di (4-methylbenzyl ester), terephthalic acid dibenzyl ester, isophthalic acid-n-butyl ester and p-toluenesulfonic acid phenyl ester; 2-benzyloxynaphthalene; It is not limited. These sensitizers may be used alone or in combination of two or more, if necessary. The amount of the sensitizer used with respect to the color developer and the color-forming dye is not particularly limited.

The dispersion liquid may further contain additives such as a filler such as kaolin clay, a dispersion aid, an antioxidant and an antifoaming agent, if necessary. That is, the heat-sensitive color forming layer formed using the dispersion liquid, if necessary, in order to further improve various physical properties and handleability, as long as it does not impair various physical properties desired for the heat-sensitive recording material, It may further include. The amount of the additive used for the color developing agent and the color forming dye is not particularly limited.

The dispersion according to the present invention uses a developer containing 2,4'-dihydroxydiphenyl sulfone as a main component, a color forming dye, and, if necessary, the above-mentioned sensitizer and additives as a dispersion medium. It is obtained by dispersing. Examples of the method for preparing the dispersion liquid include a method in which a dispersion liquid containing a color developer and a dispersion liquid containing a color forming dye are separately prepared, and then the both are mixed. The sensitizer and the additives may be added to the dispersion liquid containing the color developer, may be added to the dispersion liquid containing the color forming dye, may be added to both, or the developer may be added. The dispersion liquid containing the sensitizer and the additives may be prepared separately from the dispersion liquid containing the same or the dispersion liquid containing the color forming dye, and then mixed with each other. The dispersion liquid containing the developer has a particle size of 3 μm after adding the developer to the dispersion medium and using a disperser such as a ball mill, a sand mill, an attritor, a colloidal mill or a sand gliding mill. Hereinafter, it can be obtained by dispersing while pulverizing (wet pulverizing) so that the particle diameter is more preferably 1.5 μm or less. A dispersion containing a color forming dye and a dispersion containing a sensitizer and an additive can be obtained by the same method. The concentration of the color developer or the color-forming dye in the dispersion is not particularly limited, and the color-developing agent, the color-forming dye, the type of the dispersion medium, a combination thereof, or a method of coating the dispersion on the support. In consideration of the above, it may be appropriately set so as to obtain the optimum concentration. The specific method for preparing the dispersion is not particularly limited.

Specific examples of the support include paper such as wood free paper. Therefore, as the thermosensitive recording material, thermosensitive recording paper, that is, recording paper (output paper) of various devices represented by information communication devices such as facsimiles and information recording devices such as printers, POS (point of sales) information management system Bar code labels, various tickets, etc.

The method of coating the dispersion on a support and drying it, that is, the method of forming the thermosensitive coloring layer is not particularly limited, and various conventionally known methods can be adopted. Further, the coating amount of the dispersion liquid per unit area of the support is not particularly limited. This makes it possible to provide a heat-sensitive recording material having high color development sensitivity and excellent storage stability of the background.

[0030]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these. The thermal recording paper was evaluated by conducting a storage stability test on the background.

[Background storage stability test] The following storage stability test was carried out on a thermosensitive recording paper on which a colored image was formed by developing a color using a thermal paper coloring device (TH-PMD manufactured by Okura Electric Co., Ltd.). I went.

(Heat resistance test) First, the color density of the background of the thermal recording paper was measured (color measurement) using a Macbeth densitometer (TR-524 type). Next, the thermosensitive recording paper was kept at 80 ° C. for 24 hours using a constant temperature dryer. Then, the color density of the background of the thermosensitive recording paper was measured using a Macbeth densitometer and compared with the color density before the holding. Therefore, the smaller the difference in color density is, the higher the heat resistance of the background can be evaluated.

(Moisture and heat resistance test) First, the color density of the background of the thermal recording paper was measured using a Macbeth densitometer. Next, the above-mentioned thermal recording paper is placed at 50 ° C. and 80% relative humidity for 24 hours.
Held for hours. Then, the color density of the background of the thermosensitive recording paper was measured using a Macbeth densitometer and compared with the color density before the holding. Therefore, the smaller the difference in color density is, the more excellent the moist heat resistance of the background can be evaluated to be.

That is, the smaller the difference in color density between before and after each of the above tests, the more the thermal recording paper can be evaluated as being excellent in the storage stability of the background.

Example 1 3-Di-n-butylamino-
6-methyl-7-anilinofluorane (color forming dye) 1
0g and 10g of polyvinyl alcohol 10% by weight aqueous solution
And 80 g of water were mixed and dispersed while being pulverized with a sand grinding mill so as to have an average particle diameter of 1.5 μm or less, thereby preparing a dispersion liquid a.

On the other hand, 20 g of 2,4'-dihydroxydiphenyl sulfone having a content of trihydroxytriphenyldisulfone of 0.03% by weight, 60 g of an aqueous solution of 10% by weight of polyvinyl alcohol, and 130 g of water were mixed to carry out sand gliding. Dispersion liquid b was prepared by pulverizing and dispersing with a mill so that the average particle diameter was 1.5 μm or less.

Further, 20 g of 2-benzyloxynaphthalene (sensitizer) and 10% by weight of polyvinyl alcohol.
A dispersion solution c was prepared by mixing 10 g of the aqueous solution and 220 g of water and pulverizing them with a sand gliding mill so that the average particle diameter was 1.5 μm or less.
Was prepared.

Then, 100 g of the dispersion liquid a and the dispersion liquid b.
A dispersion liquid for forming the thermosensitive color developing layer was prepared by mixing 210 g of the dispersion liquid c, 250 g of the dispersion liquid c, and 23 g of the 30 wt% dispersion liquid of paraffin wax.

The coating amount of this dispersion was 5.0 ± after drying.
A thermosensitive coloring layer was formed on the high-quality paper by coating the high-quality paper (support) with 0.5 g / m ² and drying. That is, a heat-sensitive recording paper (heat-sensitive recording material) according to the present invention was obtained.

The above-mentioned storage stability test was conducted using the obtained thermal recording paper. As a result, in the heat resistance test, the color density before holding was 0.06, and the color density after holding was 0.07. In the moist heat resistance test, the color density before holding was 0.06, and the color density after holding was 0.0.
It was 8. Therefore, the thermal recording paper was excellent in the storage stability of the background.

[Comparative Example 1] [0041] Except that 20 g of 2,4'-dihydroxydiphenylsulfone having a trihydroxytriphenyldisulfone content of 0.2% by weight was used.
By performing the same operation as in Example 1, a thermal recording paper for comparison was obtained.

The above-mentioned storage stability test was carried out using the obtained thermosensitive recording paper. As a result, in the heat resistance test, the color density before holding was 0.06, and the color density after holding was 0.20. In the moist heat resistance test, the color density before holding was 0.06, and the color density after holding was 0.1.
It was 7. Therefore, the thermal recording paper was inferior in the storage stability of the background.

[0043]

As described above, the developer of the present invention contains 2,4'-dihydroxydiphenylsulfone as a main component containing 0.1% by weight or less of trihydroxytriphenyldisulfone as an impurity. It is a configuration including.

As a result, there is an effect that it is possible to provide a color developer suitable for obtaining a heat-sensitive recording material having high color development sensitivity and excellent storage stability of the background.

As described above, the dispersion of the present invention has a constitution in which the above-mentioned color developer and the color forming dye are dispersed in the dispersion medium. As a result, there is an effect that it is possible to provide a dispersion liquid containing a color developer suitable for obtaining a heat-sensitive recording material having high color development sensitivity and excellent storage stability of the background.

The heat-sensitive recording material of the present invention is as described above.
A heat-sensitive recording material having a heat-sensitive color-forming layer containing a color-developing agent and a color-forming dye on a support, wherein the color-developing agent has a content of trihydroxytriphenyldisulfone as an impurity of 0.1% by weight or less. 2,4′-dihydroxydiphenyl sulfone as a main component.

As a result, it is possible to provide a heat-sensitive recording material having high color development sensitivity and excellent storage stability of the background.

Continued front page    (72) Inventor Takayuki Kitahara             3-77 Kosiga, Wakayama, Wakayama Prefecture             Konishi Chemical Industry Co., Ltd. F-term (reference) 2H026 BB02 BB28 FF01

Claims (3)

[Claims] 1. A 2,4 ′ having a content of trihydroxytriphenyldisulfone as an impurity of 0.1% by weight or less.
-A color developer containing dihydroxydiphenyl sulfone as a main component. 2. A dispersion liquid comprising the color developer according to claim 1 and a color forming dye dispersed in a dispersion medium. 3. A thermosensitive recording material having a thermosensitive color developing layer containing a color developing agent and a color forming dye on a support, wherein the color developing agent has a content of trihydroxytriphenyldisulfone as an impurity of 0. A heat-sensitive recording material containing, as a main component, 2,4′-dihydroxydiphenyl sulfone in an amount of 1% by weight or less.