Thermal recording material

Details Thermal recording material Thermal recording material

2000-10-31

2004-01-13

Hess, B. Hamilton (Department: 1774)

Record receiver having plural interactive leaves or a colorless

Having a colorless color-former, developer therefor, or...

Identified organic electron acceptor other than phenolic resin

C503S209000, C503S217000, C503S221000

Reexamination Certificate

active

06677275

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a thermal recording material that has good color developing sensitivity, strong resistance to heat and good ground color.
DESCRIPTION OF THE PRIOR ART
In general, a thermal recording material having a thermally sensitive color developing layer mainly composed of colorless or pale colored dye precursor and color developing agent that develops color by reacting with said dye precursor when heated is disclosed in Japanese patent publication 45-14039 and widely used in commercial scale. A thermal printer in which a thermal head is installed is used for the recording method of said thermal recording material. Since this kind of thermal recording method superiors to the conventional recording method from the view point of noiseless at recording process, does not need developing and fixing processes, maintenance free, equipment is relatively cheap and compact and the obtained image is very clear, therefore, this method is widely applied in the field of facsimile or computer, various kinds of measuring instrument and for a labeling machine along with the growth of an information industry. The recording devices attached to these instruments are becoming more diversified and more high-performance, and the required quality to the thermal recording material is becoming more severe. Along with the miniaturization of an instrument and requirement for higher recording speed, it becomes necessary to obtain deep and clear color developing image.
For the purpose to meet the requirement, for example, in the Japanese Patent Laid open Publication 56-169087, a method to improve the color developing sensitivity by adding a thermo fusion substance to a thermally sensitive layer is disclosed, and in the Japanese Patent Laid Open Publication 56-144193, a method to improve the color developing sensitivity by using new color developing agent which has high color developing ability is disclosed. However, these methods can not be said to have a sufficient quality, because these methods have defects such as deterioration of ground color by heat, powder generation by aging and dropping of color density after preserved for long time (reprinting ability). Further, the method to use dye, color developing agent together with adequate sensitizer can be used. For example, in a case that the color developing agent is a phenol type compound represented by bisphenol A, p-benzylbiphenyl (Japanese Patent Laid Open Publication 60-82382), p-benzyloxybenzoicbenzyl (Japanese Patent Laid Open Publication 57-201691) or benzylnaphthyleter (Japanese Patent Laid Open Publication 58-87094) can be used as an adequate sensitizer. When a sensitizer is used, the sensitizer is fused in the first place and the fused sensitizer dissolves dye and color developing agent and are mixed by molecular size level so as to cause the color developing reaction, therefore, the selection of the kind of sensitizer, dye and color developing agent is very important.
Dihydroxydiphenylsulfone compound, which is used as an organic color developing agent is a well-known conventional compound, however, the color developing ability of it is too poor to meet the current requirement for high sensitivity. As the method to improve the color developing sensitivity, in Japanese Patent Laid Open Publication 4-69283, a method to add di(p-methylbenzyl)oxalate is disclosed and in Japanese Patent Laid Open Publication 8-67070, a method to add solid solution composed of two types of oxalic acid ester derivatives is disclosed. By said methods, the color developing sensitivity can be improved more or less, however, from the view points of heat resistance and quality of ground color, these methods can not be said as a sufficient ones. As mentioned above, by the conventional thermal sensitive recording medium, it is difficult to meet the current requirement to improve color developing sensitivity, further, is also difficult to meet the other requirements for quality such as to have good heat resistance and excellent of ground color.
DISCLOSURE OF THE INVENTION
The object of this invention is to provide a thermal recording material which has good color developing sensitivity, strong heat resistance of ground color and excellent ground.
The inventors of this invention have conduced an intensive study and have found that in a thermal recording material which possesses a thermally sensitive color developing layer containing colorless or pale colored basic colorless dye and an organic color developing agent as main components, the thermal recording material which contains at least one kind of dihydroxydiphenylsulfone type compound represented by following general formula (1) and containing at least one kind of sulfonamide compound represented by following general formula (2) can solve the above mentioned problems, and accomplished the present invention. Further, in this invention, more excellent color developing sensitivity can be obtained by containing 1,2-bis(phenoxymethyl)benzene.
(in this formula, R
1
and R
2
is an alkyl group or an alkenyl group of carbon number 1 to 8, or a halogen atom and a and b is an integer number of 0 to 3)
(in this formula, R
3
is an alkyl group of carbon number 1-6 or an electron attracting group and n is an integer of 0 to 2)
In general, it is concerned that the velocity of dissolution and diffusion or solubility of the dye into the melted color developing agent give the important effects to the color developing sensitivity of thermal recording material. To improve said effects, the method to add various kinds of material as a sensitizer is carried out. It is concerned that the addition of sensirizer causes several effects such as falling down of melting point, falling down of activated energy, change of polar, improvement of solubility of each materials, and the velocity for fusing, dissolving and dispersing and saturated solubility are improved. Thus the color developing sensitivity of the thermal recording material can be improved.
In this invention, the reason why is not made clear, but it is concerned that the color developing sensitivity can be improved without causing a remarkable falling down of melting point by containing a dihydroxydiphenylsulfone compound, further containing sulfonamide compound. Therefore, it is concerned that although the color developing sensitivity is improved, color developing of the ground color does not occur.
In the meanwhile, 1,2-bis(phenoxymethyl)benzene is well-known as a sensitizer, and it is confirmed that when 1,2-bis(phenoxymethyl)benzene is added besides dihydroxydiphenylsulfone compound and sulfonamide compound, the color developing sensitivity can be further improved.
Further, in this invention, when at least one kind of specific compound selected from the group composed of 4-benzyloxy-4′-(2,3-epoxy-2-methylpropoxy)diphenylsulfone, epoxy resin and diphenylsulfone bridgeable type compound are contained, it is recognized that the image preservative property of color developed part is improved. The reason why is not made clear, however, it is concerned that said specific compound is bonded with an electro charge transferring complex which is formed by the reaction between dye and color developing agent and becomes more stable state.
[in the formula, X and Y can be different and indicate a saturated or an unsaturated liner or a grafted hydrocarbon group of carbon number 1 to 12 which can possess an ether bond, or indicate
(R indicates a methylene group or an ethylene group, T indicates a hydrogen atom or an alkyl group of carbon number 1 to 4,)
and R
4
-R
9
independently indicate a halogen atom, an alkyl group or an alkenyl group of carbon number 1 to 6,
further, e, f, g, h, i, and j indicate an integer number of 0 to 4 and when are bigger than 2, R
4
-R
9
can be different,
and d is an integer of 0 to 10]
THE BEST EMBODYMENT TO CARRY OUT THE INVENTION
The thermal sensitive recording medium of this invention, for example, can be produced by following method. That is, prepare the dispersion in which a dye and compounds represe

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