JPH0432752B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention contains a leuco dye and a color developer thereof,
The present invention relates to a multicolor heat-sensitive recording material having at least two heat-sensitive coloring layers each developing a different color tone.

[Prior art]

Thermal recording materials include measurement recorders,
It is used as terminal printer paper for fax machines, computers, etc., and its demand is on the rise. In addition, with the diversification of demand for such heat-sensitive recording materials, there has been a strong demand for multi-color heat-sensitive recording materials.
Various multicolor thermosensitive recording materials have been proposed. For example, Japanese Patent Publication No. 54-36863 discloses a multicolor thermosensitive recording material that uses two or more types of coloring components (leuco dyes) that differ in the degree of decolorization by a decolorizing agent. However, when obtaining a multicolor record by combining two or more coloring components that differ in the degree of decolorization by such a decoloring agent, the degree of decolorization must be taken into consideration when selecting the coloring component. Therefore, there is a drawback that the selection of coloring components is inevitably restricted.

In leuco-based heat-sensitive recording materials, recording is obtained through a hot melting reaction between leuco dye, which is the main coloring agent, and a color developer, which is an auxiliary coloring agent. Restrictions on the selection of components means that the characteristics and quality of the recording material constituted by the coloring components are also restricted, which is not preferable. In particular, for multicolor thermosensitive recording materials, the most important quality factor is the ability to produce vivid colors in multiple tones. This restriction on selection is a very big drawback. That is, when selecting a coloring component, it is necessary to select one that simultaneously satisfies two factors: the tone of the color and the degree of decolorization by the decolorizing agent, but such selection is difficult in practice. is severely limited and poses great difficulties.

〔the purpose〕

As a result of intensive research aimed at overcoming the above-mentioned drawbacks in the prior art, the present inventors found that the decoloring effect exhibited by the decolorizing agent differs depending on the color developer in the color forming layer, and We discovered that by applying this phenomenon to multicolor thermosensitive recording materials, it is possible to form multicolor images with high contrast and clarity.
The present invention has now been completed.

〔composition〕

That is, according to the present invention, in a multicolor heat-sensitive recording material having at least two heat-sensitive coloring layers containing a leuco dye and a color developer thereof and each developing a color in a different tone, the leuco dye and the color developer are combined. A color erasing agent having a color erasing effect on the color development reaction is contained in at least one layer of the heat-sensitive color forming layer, or is interposed as a color erasing agent layer between the heat-sensitive color forming layers, and each of the heat-sensitive color forming layers A multicolor thermosensitive recording material is provided, characterized in that the color developer contained in the layer is a color developer that has a different color erasing effect depending on the color erasing agent.

In the present invention, unlike the prior art, a combination of a color erasing agent and a color developer is used, and as the color developer, those having different color erasing effects are selected. Therefore, in the case of the present invention, unlike the conventional case in which coloring components are selected in relation to the decolorizing agent, the decoloring effect of the decolorizing agent is controlled by the color developer. The quality required of the coloring agent is simply a difference in decoloring effect, and is not limited by the color tone of the coloring agent. Therefore, in the case of the present invention, the use of coloring components can be freely selected, and it becomes easy to obtain clear multicolor recordings.

The multicolor heat-sensitive recording material of the present invention will be explained in more detail below. Basically, this multicolor heat-sensitive recording material has a plurality of heat-sensitive coloring layers formed on a support (paper, synthetic paper, resin film, etc.). However, if necessary, it is possible to form a self-supporting layer by pouring or kneading the main coloring agent, coloring aid, etc. of the heat-sensitive coloring layer that is originally in contact with the support into the support. can. In the present invention, the multi-layered thermosensitive coloring layer on the support is laminated in the order according to the heat-sensitive temperature, and the lower layer (the thermosensitive coloring layer closer to the support) is the upper layer (the thermosensitive coloring layer closer to the surface of the thermosensitive recording material). It is preferable to use a layer having a higher heat-sensitivity temperature than that of the heat-sensitive color forming layer), and the color tones of the upper and lower layers are different from each other.

In the present invention, a color erasing agent is used in combination with a color developer, and in this case, the color erasing agent is used in at least one layer of a plurality of heat-sensitive color forming layers, that is, each heat-sensitive color forming layer or the heat-sensitive color forming layer. It can be contained in a specific color forming layer, or it can be interposed as a decoloring agent layer between each heat-sensitive color forming layer.

In the present invention, each color developer contained in a plurality of heat-sensitive color forming layers has a different color erasing effect due to the color erasing agent, and when using it,
For example, regarding the color erasing effect provided by a color erasing agent, a color developer with a large effect can be contained in the low temperature coloring layer, and a developer with a small effect can be contained in the high temperature coloring layer. When using such a structure, the coloring effect of the low-temperature coloring layer is large during high-temperature heating, so 2.
Multicolor recording with excellent color separation can be performed. Note that the decoloring effect as used in the present invention refers to a phenomenon in which the color developing ability of a color developer is reduced by a decolorizing agent.

Leuco dyes used as coloring components in the present invention include those shown below.

(1) Leuco base of triphenylmethane dye (In the formula, Rx, Ry and Rz are hydrogen, hydroxyl group, halogen, alkyl group, nitro group, amino group, dialkylamino group, monoalkyl group, and allyl group) Specific examples of the above compounds are as follows.

3,3-bis(p-dimethylaminophenyl)
-phthalide 3,3-bis(p-dimethylaminophenyl)
-6-dimethylaminophthalide 3,3-bis(p-dimethylaminophenyl)
-6-diethylaminophthalide 3,3-bis(p-dimethylaminophenyl)
-6-Chlorphthalide 3,3-bis(p-dibutylaminophenyl)
Phthalide(2) Leuco base of fluorane dyes (In the formula, Rx, Ry and Rz are the same as in (1) above.) Specific examples of the above compounds are as follows.

3-Cyclohexylamino-6-chlorofluorane 3-(N,N-diethylamino)-5-methyl-
7-(N,N-dibenzylamino)fluorane 3-dimethylamino-5,7-dimethylfluorane 3-diethylamino-7-methylfluorane 3-diethylamino-7,8-benzfluorane 3-diethylamino-6- Methyl-7-chlorofluorane 3-pyrrolidino-6-methyl-7-anilinofluorane 2-{N-(3'-trifluoromethylphenyl)
amino}-6-diethylaminofluorane 2-{3,6-bis(diethylamino)-9-
(O-chloroanilino)xantylbenzoic acid lactam} (3) Lactone compound represented by the following general formula (In the formula, R ₁ and R ₂ are hydrogen, lower alkyl group, substituted or unsubstituted phenyl group, cyanoethyl group, β
- represents a hydroxyethyl group or a β-halogenated ethyl group, or R ₁ and R ₂ are combined (-
_CH2 ) _-4 , ( _-CH2 ) _-5 or ( _-CH2 ) _-2O (-)-CH
₂ )−
₂ , R ₃ and R ₄ are hydrogen, lower alkyl group,
represents an aralkyl group, an amino group or a phenyl group, one of R ₃ and R ₄ is hydrogen, and X ₁ ,
X ₂ and X ₃ are hydrogen, lower alkyl group, lower alkoxyl group, halogen atom, halogenated methyl group,
represents a nitro group, an amino group or a substituted amino group, X ₄ represents hydrogen, halogen, a lower alkyl group or a lower alkoxyl group, and n is 0 or 1 to
(represents an integer of 4) Specific examples of the above compounds are as follows.

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-4'-chloro-5'-
Methyl phenyl) phthalide In addition, as a color developer that reacts with the heat-sensitive color former to develop color, electron-accepting ones are used, such as the following phenolic substances, acidic substances, and their derivatives. can be mentioned.

(1) Phenolic substances 3,5-xylenol, thymol, P-tert-
Butylphenol, 4-hydroxyphenoxide, methyl-4-hydroxybenzoate, 4-
Hydroxyacetophenone, α-naphthol, β
-naphthol, catechol, resorcil, hydroquinone, 4-tert-octylcatechol, 4,
4'-sec-butylidenephenol, 2,2-dihydroxydiphenyl, 2,2'-methylenebis(4
-methyl-6-tert-butylphenol), 2,
2'-bis(4'-hydroxyphenyl)propane,
4,4'-isopropylidene-bis(2-tert-butyphenol), 4,4'-sec-butylidene diphenol, pyrogallol, phloroglucin, phlorodarcin carboxylic acid, (2) Acidic substances boric acid, oxalic acid, maleic acid Acid, tartaric acid, citric acid, succinic acid, benzoic acid, stearic acid, gallic acid, salicylic acid, 1-hydroxy-2-naphthoic acid, o-hydroxybenzoic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid benzyl ester, o-chlorobenzyl p-hydroxybenzoate, m-hydroxyaniline-arylamide,
2-Hydroxy-p-toluic acid.

Among these, those that have a particularly large decolorizing effect from decolorizing agents include benzyl p-hydroxybenzoate, o-chlorobenzyl p-hydroxybenzoate, m-hydroxyaniline-arylamide, etc. 2,2'-methylenebis(4-methyl-6-
tert-butylphenol), 2,2'-bis(4'-hydroxyphenyl)propane, and 4,4'-isopropylidene-bis(2-tert-butyphenol).

The multicolor thermosensitive recording material of the present invention is a recording material that utilizes the difference in the decoloring effect of color developers, and is a recording material that uses a combination of a color developer with a particularly large decolorizing effect and a color developer with a particularly small color decolorizing effect as described above. By using this method, it becomes possible to obtain a clear multicolor image.

Further, as an auxiliary component for forming the heat-sensitive layer, an organic polymer compound as shown below is used as a binder.

polyvinyl alcohol, methoxycellulose,
Hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, starch, gelatin, polystyrene, vinyl chloride-vinyl acetate copolymer, polybutyl methacrylate, polyvinyl chloride, styrene-butadiene copolymer, chlorinated rubber, etc.

Examples of the decolorizing agent used in the present invention include the following.

(1) Alkylene oxide adducts of bisphenols (Japanese Patent Application Laid-open No. 139741-1983) Here, A represents methylene or alkylidene.

(2) Ethylene oxide adduct of terephthalic acid (Japanese Patent Application Laid-Open No. 1983-25306) (3) Long-chain 1,2-glycol (Japanese Patent Application Laid-open No. 1983-27217) Here, R represents an alkyl group.

(4) Glycerin fatty acid ester (Japanese Patent Publication No. 55-113593) (5) Urea derivative (Japanese Patent Application Publication No. 55-139290) (6) Alkylene oxide adduct of linear glycol (Japanese Patent Application Publication No. 55-152094) Here, R represents an alkyl group.

(7) Morpholine derivatives (Japanese Patent Publication No. 56-40588) (8) Solid alcohol (Japanese Patent Publication No. 50-17865) (9) Polyether or polyethylene glycol derivatives (Japanese Patent Publication No. 50-17867 and Patent Publication No. 17868) (10) Nitrogen-containing crystalline organic compound (Japanese Patent Publication No. 51-19991) (11) Guanidine derivative (Japanese Patent Publication No. 51-29024) (12) Amine or quaternary ammonium salt (Japanese Patent Publication No. 50-18048) Further, in the heat-sensitive coloring layer, , silica, magnesia,
By adding fine powders such as talc, calcium carbonate, barium sulfate, aluminum stearate, urea-formalin resin, styrene resin, etc.
It is desirable to improve the clarity of colored images.
In addition, when coating and forming a thermosensitive coloring layer on a support or a lower thermosensitive coloring layer, antifoaming agents, wetting agents (surfactants), waxes, etc. are added to the thermosensitive coloring layer forming liquid.
Coating properties and responsiveness can be improved by adding a softening point regulator or the like. Furthermore, an intermediate layer containing a decoloring agent may be provided between the thermosensitive coloring layer and the other thermosensitive coloring layer.

In order to produce the multicolor heat-sensitive recording material of the present invention, the leuco dye and color developer are separately mixed with a decolorizing agent, a binder, and other additives using a dispersing machine such as a ball mill, attritor, or sand mill. After pulverizing and dispersing the particles, they may be mixed to prepare a thermosensitive coloring layer forming liquid, which may be used to form a plurality of thermosensitive coloring layers on a support.

〔effect〕

In the present invention, in relation to the color erasing agent, color developers with different color erasing effects are applied to each heat-sensitive coloring layer, and the color erasing effect during heat-sensitive coloring is controlled by each color developer. Because of this, there are no restrictions on the selection of leuco dyes as coloring components, and it is easy to obtain multicolor images with high color separation and clarity.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that both "parts" and "%" shown below are based on weight.

Example 1 A high temperature thermosensitive coloring layer forming liquid and a low temperature thermosensitive coloring layer forming liquid were prepared as shown below.

High-temperature thermosensitive color forming layer forming liquid: Mix the following components for 10 hours using a ball mill to prepare leuco dye dispersion A, color developer dispersion B, and decolorizer liquid C, and then mix each of these liquids A. , B, and C were sufficiently mixed to prepare a high temperature thermosensitive coloring layer forming liquid.

Components of dispersion A 3-diethylamino-7-O-chloroanilinofluorane 4.0 parts Polyvinyl alcohol (10% aqueous solution) 13.2〃 Water 15.8〃 Components of dispersion B 2,2'-bis(4'-hydroxyphenyl ) Propane 13.5 parts Polyvinyl alcohol (10% aqueous solution) 12.3〃 Water 7.2〃 Components of decolorizer liquid C Ether made by adding ethylene oxide to bisphenol A 5.0 parts Type glycol Polyvinyl alcohol (10% aqueous solution) 9.0〃 Water 20.0 〃 Low-temperature thermosensitive coloring layer forming liquid: Mix the following components for 10 hours using a ball mill to prepare leuco dye dispersion D and color developer dispersion E, respectively. A thermosensitive coloring layer forming solution was prepared.

Component of Dispersion D 3-diethylamino-7-chlorofluorane
3.0 parts Stearamide 24 Hydroxyethyl cellulose (10% aqueous solution)
24〃 Water 20.6〃 Components of dispersion E p-hydroxybenzoic acid benzyl ester
10.0 parts 10% hydroxyethyl cellulose aqueous solution 25〃 Water 15〃 The high-temperature heat-sensitive color forming layer forming liquid prepared as above was applied to the surface of high-quality paper (50 g/m ² ) using a wire bar, and dried to reduce the amount of adhesion. A high temperature thermosensitive coloring layer of 6.2 g/m ² is formed, and then a low temperature thermosensitive coloring layer forming liquid is applied and dried to form a low temperature thermosensitive coloring layer with a coating weight of 2.3 g/m ² to form a multicolor thermosensitive layer of the present invention. Obtained recording materials. The multicolor thermosensitive recording material obtained in this way has
When printed at a temperature of 100°C using a thermal printer with a built-in thermal head, a clear red image was obtained, and when printed at a temperature of 145°C, a clear black image was obtained, which was recorded as a thermal head. Even if the contact time with the material was significantly shortened, sufficient image density was obtained for both low-temperature and high-temperature colored images. Furthermore, the image in this case was extremely clear, with no low-temperature colored image remaining in the peripheral areas of the high-temperature colored image.

Example 2 A high temperature thermosensitive color forming layer forming liquid was prepared as shown below.
A low temperature thermosensitive coloring layer forming liquid and a color erasing layer forming liquid were prepared.

High temperature thermosensitive color forming layer forming liquid: Mix the following components for 10 hours using a ball mill to prepare a leuco dye dispersion (A-2) and a color developer dispersion (B-2). −
2) and (B-2) were sufficiently mixed to prepare a high temperature thermosensitive coloring layer forming liquid.

Components of dispersion (A-2) 3-diethylamino-7-o-chloroanilinofluorane 6.2 parts Polyvinyl alcohol (10% aqueous solution) 20.0〃 Water 23.8〃 Components of dispersion (B-2) 4,4'- Isopropylidene-bis(2-tert-
Butifue 22.0 parts Nor) Polyvinyl alcohol (10% aqueous solution) 20.0〃 Water 8.0〃 Low-temperature thermosensitive coloring layer forming liquid: The following components were mixed for 10 hours using a ball mill, and leuco dye dispersion (D-2) and color developer were prepared. After preparing the agent dispersion (E-2), the dispersion (D-
2) and (E-2) were thoroughly mixed to prepare a low temperature thermosensitive coloring layer.

Components of dispersion liquid (D-2) Components of dispersion liquid (E-2) same as dispersion liquid D of Example 1 o-chlorobenzyl p-hydroxybenzoate
10.0 parts Oxidized starch (10% aqueous solution) 25.0〃 Water 15.0〃 Decolorizing layer forming liquid: The following components were mixed for 5 hours using a ball mill to prepare a decoloring layer forming liquid (C-2).

Ether obtained by adding ethylene oxide to bisphenol A 15.0 parts Glycol methylolamide 2.0〃 Polyvinyl alcohol (15% aqueous solution) 30.0〃 Water 53.0〃 The high temperature heat-sensitive coloring layer forming liquid prepared as above was mixed using a wire bar. The coating was applied to the surface of high-quality paper (50 g/m ² ) and dried to form a high-temperature heat-sensitive coloring layer with a coating weight of 5.8 g/m ² .Then, a decolorizing layer forming solution was applied, dried, and then low-temperature heat-sensitive coloring was applied. Apply layer forming liquid,
It was dried to form a low temperature thermosensitive coloring layer having an adhesion amount of 2.1 g/m ² to obtain a multicolor thermosensitive recording material of the present invention.

When the thus obtained recording material was printed at temperatures of 100° C. and 145° C. in the same manner as in Example 1, clear red and black images similar to those in Example 1 were obtained.

The present invention utilizes the difference in the decoloring effect of color developers to obtain multicolor images with excellent clarity. In Example 1, p-hydroxybenzoic acid benzyl ester is 2′-bis(4′-
hydroxyphenyl)propane, and in Example 2, o-chlorobenzyl p-hydroxybenzoate is more effective than 4,4'-propane.
It takes advantage of the fact that it has a greater color erasing effect than isopropylidene-bis(2-tert-butyphenol).

Next, in order to evaluate the images of the multicolor heat-sensitive recording material of the present invention, two-color Experimental heat-sensitive recording materials were produced and compared with the products of Examples 1 and 2.

First, 2, which has a small decolorizing effect as a color developer.
When printing on a recording material obtained by using 2'-bis(4'-hydroxyphenyl)propane in both the low-temperature and high-temperature coloring layers, both products exhibit a The low-temperature colored image was insufficiently erased, the low-temperature colored image remained in the peripheral areas of the high-temperature colored image, and a decrease in contrast and deterioration in image clarity was observed compared to the image of the multicolor thermosensitive recording material of the present invention. It was done. Next, when printing on a recording material obtained using p-hydroxybenzoic acid benzyl ester, which has a large color erasing effect, as a color developer, the color of the high-temperature colored image when printed at high temperature was reduced in all products. This resulted in an unclear image with a lower density than that of the multicolor thermosensitive recording material of the present invention.

From the results of the above comparisons, it is clear that the images of the multicolor heat-sensitive recording material of the present invention are excellent in clarity, contrast, and the like.

Claims (1)

[Claims] 1. In a multicolor thermosensitive recording material containing at least two thermosensitive coloring layers containing a leuco dye and its color developer and each developing a color in a different tone, a color erasing method is provided in response to the coloring reaction between the leuco dye and the developer. A decoloring agent having an effect is contained in at least one layer of the heat-sensitive coloring layer, or a decoloring agent is interposed between the heat-sensitive coloring layers as a decoloring agent layer, and a color developer is contained in each of the heat-sensitive coloring layers. A multicolor thermosensitive recording material characterized in that the decoloring agents each have a different decoloring effect.