JPH054443A - Thermal recording body and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a thermal recording body, from which a distinct recording image is obtained by erasing a color-developed thermal color-developing layer by heating, and simple manufacture thereof, and to form even the recording image being effective as a negative type thermal recording body and utilizing the color tone and texture of the surface of a supporter. CONSTITUTION:A color-developed thermal color-developing layer and an erasing layer containing an erasing agent are laminated successively onto a supporter. A tranparent film, a colored sheet, etc., can be employed as the supporter. The thermal color-developing layer may be constituted of a leuco group color developing layer containing leuco dyes and a colorant, and piperidines, amidines or the di-substituted amides of aromatic carboxylic acid is used preferably as the erasing agent at that time. The color-developed thermal color-developing layer is acquired by drying at high temperature after the coating of a coating fluid on an aqueous group coating fluid and at the stage of the preparation of the coating fluid on an organic solvent group coating fluid respectively.

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 material, and more particularly to a heat-sensitive recording material for obtaining a clear recorded image by decoloring a heat-sensitive color-developing layer formed by heating, which is effective as a negative type heat-sensitive recording material. The present invention also relates to a heat-sensitive recording material capable of forming a recorded image by utilizing the background of the support surface.

[0002]

2. Description of the Related Art A thermosensitive recording medium is known in which a colored image is obtained by contacting a coloring substance with heat by utilizing a coloring reaction between a colorless or light-colored leuco dye and an organic or inorganic coloring agent. Therefore, a support using a film or a synthetic paper as a support, and a two-color type thermal recording material have been proposed depending on the use. Further, since the thermal recording material is inexpensive and the device is simple, the demand thereof is increasing more and more.

On the other hand, in the medical field, an X-ray imaging device,
Various machines such as an ultrasonic imaging device and an X-ray CT are used. At this time, the displayed image is recorded using various image recording devices. However, since any image recording apparatus uses an optical system, a fixing / developing process is required and the apparatus tends to be large. On the other hand, the thermal recording method using a thermal head is expected in the medical field because it requires no development, is easy to handle, and is inexpensive. However, since images in the medical field are much larger in the printed portion than in the blank portion, the thermal head in an ordinary thermal recording apparatus may be overheated and damaged. Therefore, development of a negative type thermal recording material is desired. Further, various negative films for photo and plate making are relatively expensive, and the process up to film formation is complicated. Therefore, the development of a negative type thermal recording material is also desired here.

[0004]

As a negative type thermal recording medium, for example, a recording medium utilizing microcapsules has been proposed in Japanese Patent Application Laid-Open No. 2-160580.
However, the recording medium using the capsule has the drawbacks that the manufacturing cost is high, the process is complicated, and the sensitivity is insufficient. Therefore, the inventors of the present invention have earnestly studied a recording material capable of forming a negative-type recording image at a low cost by a simple method, and as a result, a decolorizing layer containing a decoloring agent is laminated on a thermosensitive coloring layer which has been colored, It was found that when a heat-sensitive color-developing layer in which a color-erasing agent in the color-erasing layer is colored by heating is caused to act, a clear recorded image with extremely high sensitivity can be obtained, thereby completing the present invention.

[0005]

The thermal recording material of the present invention comprises:
A thermosensitive recording medium comprising a support, and a thermosensitive coloring layer that has developed a color and a decoloring layer containing a decoloring agent, which are sequentially laminated on the support.

[0006]

In the heat-sensitive recording material of the present invention, various supports can be used, but since the heat-sensitive color forming layer tends to be transparent during recording, for example, when a transparent film is used as the support, a projector is used. A negative-type transparent recording image that can be used for is formed. Further, when a sheet colored in a color tone different from that of the thermosensitive coloring layer is used as a support, a sharp and clear recorded image can be obtained due to the color tone of the support and the contrast with the background. As the transparent film, for example, a film of ethylene resin, propylene resin, styrene resin, vinyl chloride resin, ester resin, polyamide resin, acrylic resin, nitrile resin, urethane resin, cellulose resin or the like is appropriately selected and used. To be done.

The color-developed thermosensitive coloring layer formed on these supports is preferably formed of a leuco coloring layer containing a leuco dye and a coloring agent, and a colorless or light-colored layer constituting the leuco coloring layer is formed. As the leuco dye, the leuco dye used in an ordinary thermosensitive recording medium can be used as it is.
Specifically, one or more of various triarylmethane dyes, diphenylmethane dyes, thiazine dyes, spiro dyes, lactam dyes, fluorane dyes, fluorene dyes, etc. are appropriately selected and used.

As the coloring agent that reacts with these leuco dyes to give a color, the coloring agents used in ordinary heat-sensitive recording materials can be used. Specifically, various aromatic carboxylic acid coloring agents can be used. Agent,
One or more of phenolic colorants, phenolic resin colorants, metal complex compound colorants and the like are appropriately selected and used. The coloring agent is used in an amount of 1 to 30 parts by weight, preferably 1 to 8 parts by weight, based on 1 part by weight of the dye. Further, in the thermosensitive color-developing layer, an adhesive is blended in addition to the leuco dye and the coloring agent. The adhesive is appropriately prepared depending on whether the coating liquid is prepared in an aqueous system or an organic solvent system. To be selected. In the case of an aqueous coating liquid, a usual water-soluble or water-dispersible adhesive is used, and in the case of an organic solvent-based coating liquid, resins soluble in an organic solvent, particularly a thermoplastic resin is preferably used. To be done. The amount of the adhesive used is generally 1 to 90% by weight, preferably 5 to 60% by weight of the total solid content of the thermosensitive coloring layer.
It is adjusted in the range of about wt%. Further, in the color forming layer forming coating liquid, various heat-fusible substances, pigments, lubricants, dispersants, ultraviolet absorbers, defoamers, fluorescent dyes, coloring dyes, other auxiliaries and the like are further appropriately mixed. You may.

When the heat-sensitive recording material of the present invention is manufactured, it is necessary to uniformly color the heat-sensitive color forming layer before forming the decoloring layer. When the heat-sensitive coloring layer is prepared with an aqueous coating liquid, a uniform coloring layer can be formed by applying the coating liquid on the support and then drying at high temperature.
The drying conditions are appropriately adjusted in consideration of the coating amount of the coating liquid, the drying temperature, the drying time, etc. For example, the coating amount is 2 by dry weight.
When it is about 5 g / m ² , it may be dried at a temperature of 80 ° C. or higher for about 5 minutes.

Further, when the thermosensitive coloring layer is prepared with an organic solvent-based coating liquid, the leuco dye and the color former are dissolved in the organic solvent during the preparation of the coating liquid to form a uniform color-forming coating liquid. It becomes unnecessary. However, since an organic solvent is used, it is necessary to take safety and equipment into consideration. The organic solvent is preferably a solvent that dissolves both a leuco dye and a coloring agent, and is, for example, at least selected from hydrocarbons, halogenated hydrocarbons, alcohols, ether / acetals, ketones and esters. One type is preferably used.

In the heat-sensitive recording material of the present invention, the decoloring layer containing the decoloring agent is formed on the color-forming layer thus formed, but the decoloring agent is not particularly limited, and the usual two-color heat-sensitive layer is used. An erasing agent used in a recording material or the like is appropriately selected and used. Specifically, for example, aliphatic amines, piperidines, piperazines, pyridines, imidazoles, imidazolines, morpholines, guanidines, amidines, polyethers, glycols, disubstituted amides of aromatic carboxylic acids. And the like, particularly preferably piperidines, amidines, di-substituted amides of aromatic carboxylic acids, and the like.

Among them, tetrakis (2,2,6,6-
Tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, tetrakis (1,2,2)
2,6,6-pentamethyl-4-piperidyl) -1,
2,3,4-butane tetracarboxylate, {1,
2,2,6,6-pentamethyl-4-piperidyl / β,
β, β ′, β′-tetramethyl-3,9- [2,4,
Piperidines such as 8,10-tetraoxaspiro (5,5) undecane] diethyl} -1,2,3,4-butanetetracarboxylate and N, N'-isophthaloyl-di (N-cyclohexyl-N-methylamide) ) And N, N '
Disubstituted amide compounds of aromatic carboxylic acids such as -terephthaloyl-di (N-phenyl-N-ethylamide) are most preferably used because they are excellent in the decoloring effect of the color forming layer.

These decoloring agents are generally used in the decoloring layer in an amount of 0.1 to 2 based on the total weight of the leuco dye and the color developing agent in the thermosensitive coloring layer.
It is contained in an amount of about 0 times by weight, preferably 0.5 to
It is adjusted in the range of about 6 times by weight. Incidentally, it is of course possible to use two or more kinds of decolorizing agents together. In addition, various adhesives, dispersants, lubricants,
Auxiliary agents such as a heat-fusible substance, an inorganic pigment, an organic pigment, an antifoaming agent, an ultraviolet absorber, a fluorescent dye, and a dye can be appropriately mixed. Further, in order to enhance transparency, the decolorizing layer of the present invention may be configured as a whole by mainly forming a layer containing a decoloring agent and a layer containing another material.

In the heat-sensitive recording material of the present invention, in order to form a recorded image utilizing the color tone of the surface of the support and the background, an auxiliary agent that makes the heat-sensitive coloring layer and the decoloring layer concealable too much. Is preferably avoided. For example, when a pigment is blended in the heat-sensitive color developing layer or the decoloring layer, it is about 1 to 30% by weight, preferably 2 to 25% by weight based on the total solid content of each layer.
It is desirable to use a pigment having an average particle size of 0.3 to 4 [mu] m, preferably 0.5 to 2 [mu] m, in the range of about wt%. In addition, it is desirable to avoid the use of a pigment that is bleached by heating, and depending on the application, an auxiliary agent that increases transparency by heating may be added.

In the heat-sensitive recording material of the present invention, the coating liquid for forming the heat-sensitive color developing layer and the color erasing layer is sequentially coated on the support by a coating method such as air knife coating, blade coating, bar coating and gravure coating. To be dried. The coating amount of the thermosensitive coloring layer is generally about 1 to 12 g / m ² , preferably ² to 8 g / m ² in terms of dry weight.
adjusted with m ² range of about, the coating amount of the decolorizing layer coating solution is generally 1 to 15 g / m ² approximately by dry weight, preferably 2 to
It is adjusted within the range of about 10 g / m ² .

In the heat-sensitive recording material of the present invention, a protective layer containing a water-soluble polymer as a main component may be formed on the erasing layer, and by forming the protective layer, a chemical agent or a plasticizer is used. Such a structure is one of the preferred embodiments of the present invention because discoloration and fading are prevented. Further, various known techniques in the heat-sensitive recording material manufacturing field can be appropriately added, such as providing an antistatic layer or a protective layer on the back surface of the support, and further processing the back surface of the support with an adhesive.

[0017]

The present invention will be described in more detail by way of the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in the examples represent "parts by weight" and "% by weight", respectively.

Example 1 [Preparation of solution A] 3- (N-methyl-Nn-hexylamino) -6-methyl-7-phenylaminofluorane 20 parts 4-hydroxy-4'-isopropoxydiphenyl sulfone 20 parts 1,2-bis (3-methylphenoxy) ethane 10 parts 5% aqueous solution of methylcellulose 20 parts water 80 parts This composition was ground with a sand mill until the average particle size became 3 μm. [Preparation of solution B] Tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate 50 parts 5% aqueous solution of methylcellulose 25 parts water 110 parts This composition The product was ground with a sand mill until the average particle size became 3 μm. [Preparation of coating solution for thermosensitive coloring layer] 100 parts of A liquid, 60 parts of 50% styrene-butadiene copolymer latex, and 60 parts of water were mixed and stirred to prepare a coating solution for thermosensitive coloring layer. [Preparation of Decoloring Layer Coating Solution] 175 parts of Solution B, 50 parts of a 20% aqueous solution of oxidized starch and 60 parts of water were mixed and stirred to prepare a decoloring layer coating solution. [Preparation of protective layer coating solution] 15% polyvinyl alcohol 1
00 parts, 10 parts of kaolin having an average particle diameter of 1 μm, and 60 parts of water were mixed and stirred to prepare a protective layer coating liquid. [Formation of thermosensitive recording medium] A transparent polypropylene film having a thickness of 60 μm was coated with a coating solution for the thermosensitive coloring layer so that the coating amount after drying was 2.5 g / m ^2, and dried at 140 ° C. for 2 minutes. A thermosensitive color developing layer that was uniformly colored was formed. Then, the decoloring layer coating liquid and the protective layer coating liquid were applied and dried on the color forming layer so that the coating amounts after drying were both 3 g / m ² to obtain a thermosensitive recording medium.

When the obtained heat-sensitive recording material was recorded with a heat-sensitive facsimile (trade name: Panafax UF-5E, manufactured by Matsushita Electric Transport Co., Ltd.), a clear transparent recording image was formed. This recording material could be observed with a projector as a negative type recording image. Further, ethanol was attached to the recording portion, and the occurrence of fog in the recorded image was observed, but no fog occurred.

Example 2 In preparation of solution A, 3- (N-ethyl-N-isobutyl) was used instead of 3- (N-methyl-Nn-hexylamino) -6-methyl-7-phenylaminofluorane. Amino) -6-methyl-7-phenylaminofluorane was used, and 4,4′-isopropylidenediphenol was used instead of 4-hydroxy-4′-isopropyloxydiphenyl sulfone. A thermal recording material was formed in the same manner and evaluated in the same manner, and the same quality evaluation as in Example 1 was obtained.

Example 3 In preparation of solution B, tetrakis (1,2,2,6,6-
N, N′-isophthaloyl-di (N-cyclohexyl-N-methylamide) was used in place of pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, and the thickness was 85 μm as a support. A thermosensitive recording medium was formed in the same manner as in Example 1 except that the colored sheet of No. 1 was used.

When the obtained heat-sensitive recording material was recorded by a heat-sensitive facsimile (trade name: Panafax UF-5E, manufactured by Matsushita Electric Transport Co., Ltd.), a recorded image in which the colored surface of the coloring sheet was clearly recognized was formed. Further, ethanol was attached to the recording portion, and the occurrence of fog in the recorded image was observed, but no fog occurred.

Comparative Example 1 A thermosensitive recording medium was obtained in the same manner as in Example 1 except that the drying condition of the thermosensitive coloring layer of Example 1 was 60 ° C. for 2 minutes.
Uniform coloring of the thermosensitive coloring layer was not obtained, and only an unclear recorded image was obtained.

Example 4 [Preparation of liquid C] 3- (N-methyl-Nn-hexylamino) -6-methyl-7-phenylaminofluorane 15 parts 4-hydroxy-4'-isopropoxydiphenyl sulfone 15 parts Styrene / ethyl acrylate copolymer 10 parts Toluene 70 parts This composition was mixed and stirred to prepare a thermosensitive color developing layer coating liquid in which uniform color was developed. [Preparation of Decoloring Layer Coating Liquid] Liquid B 185 used in Example 1
Parts, mixed with 50 parts of 20% aqueous solution of oxidized starch and 65 parts of water.
The solution was stirred to give a decolorizable layer coating solution. [Preparation of coating liquid for protective layer] 15% polyvinyl alcohol 4
0 part, 7 parts of kaolin having an average particle diameter of 1 μm, and 60 parts of water were mixed and stirred to prepare a protective layer coating liquid. [Formation of thermosensitive recording medium] On a transparent polypropylene film having a thickness of 60 μm, the above-mentioned coating solution for thermosensitive coloring layer, which was uniformly colored, was applied and dried so that the coating amount after drying was 3 g / m ² . Then, the decolorizing layer coating liquid and the protective layer coating liquid on the color forming layer,
The coating amount after drying to obtain a heat-sensitive recording material was coated and dried so as to 4g / m ² and 2 g / m ^2, respectively.

When the obtained heat-sensitive recording material was recorded with a heat-sensitive facsimile (trade name: Panafax UF-5E, manufactured by Matsushita Electric Transport Co., Ltd.), a clear transparent recorded image was formed. This recording material could be observed with a projector as a negative type recording image. Further, ethanol was attached to the recording portion, and the occurrence of fog in the recorded image was observed, but no fog occurred.

Example 5 In preparation of solution C, 3- (N-methyl-N-isoamyl) was used instead of 3- (N-methyl-Nn-hexylamino) -6-methyl-7-phenylaminofluorane. Example 4 except that amino) -6-methyl-7-phenylaminofluorane was used and 4,4'-isopropylidenediphenol was used instead of 4-hydroxy-4'-isopropyloxydiphenyl sulfone. A thermosensitive recording medium was formed in the same manner and evaluated in the same manner, and the same quality evaluation as in Example 4 was obtained.

Example 6 In preparation of solution B, tetrakis (1,2,2,6,6-
Instead of pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, {1,2,
2,6,6-pentamethyl-4-piperidyl / β, β,
β ′, β′-tetramethyl-3,9- [2,4,8,10
-Tetraoxaspiro (5,5) undecane] diethyl} -1,2,3,4-butanetetracarboxylate was used to form a thermosensitive recording medium in the same manner as in Example 4 and evaluated in the same manner. The same quality evaluation as in Example 4 was obtained.

[0028]

As is apparent from the results of the examples, in the heat-sensitive recording material of the present invention in which the decoloring layer containing the decoloring agent is laminated on the color-developing thermosensitive coloring layer, the heat-sensitive recording medium of The decoloring agent of (1) effectively acted on the thermosensitive color-developing layer, and a clear recorded image could be obtained with extremely high sensitivity. Further, it was effective as a negative-type heat-sensitive recording material, and it was possible to form a recorded image by utilizing the background of the support surface. Moreover, it became clear that such a recording medium can be manufactured by an extremely simple method.

Claims (8)

[Claims] 1. A heat-sensitive recording material comprising a support and a heat-sensitive color-developing layer for coloring, and a decoloring layer containing a decoloring agent, which are sequentially laminated on the support. 2. The thermosensitive recording medium according to claim 1, wherein the support is a transparent film. 3. The heat-sensitive recording material according to claim 1, wherein the decoloring agent is at least one selected from piperidines, amidines and disubstituted amides of aromatic carboxylic acids. 4. The heat-sensitive recording material according to claim 3, wherein the color-developing layer is a leuco-based color-developing layer containing a leuco dye and a coloring agent. 5. The heat-sensitive recording material according to claim 1, further comprising a protective layer containing a water-soluble polymer as a main component on the decoloring layer. 6. An organic solvent-based thermosensitive color forming layer-forming coating liquid, in which a leuco dye and a color former are dissolved to form a color, is applied on a support and dried, and then a decoloring agent is contained on the color forming layer. A method for producing a thermosensitive recording medium, which comprises applying and drying a decolorizable layer forming coating liquid. 7. The method according to claim 6, wherein the organic solvent is at least one selected from hydrocarbons, halogenated hydrocarbons, alcohols, ether / acetals, ketones and esters. 8. An aqueous thermosensitive coloring layer-forming coating liquid containing a leuco dye and a coloring agent is applied on a support, dried at high temperature to develop a color, and then a decoloring agent is contained on the coloring layer. A method for producing a thermosensitive recording medium, which comprises applying and drying a decolorizable layer forming coating liquid.