JPH09109559A - Light-fixing type heat-sensitive recording medium and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a good image recording by decreasing color development caused by precoupling in preparing a coating liq. and decreasing optical density of the ground skin part. SOLUTION: A method for preparing a light-fixing type heat-sensitive recording medium prepd. by applying a dispering liq. of a mixture of a diazonium salt 16 wrapped in a microcapsule, a coupler 18 and a basic compd. 20 on a substrate and drying it, is provided. When the microcapsule encapsulating the diazonium salt 16 is prepd., at first, the microcapsule wall is formed in a water- existing liq. by means of an interfacial polymn. method so as to wrap the diazonium salt in the microcapsule and then, a salt with a tetraphenyl borate group is incorporated in the water-existing liq. to substitute only the diazonium salt dissolved in the water phase in the water-existing liq. with the tetraphenyl borate salt by the time where the microcapsule wall is formed and then, the tetraphenyl borate salt is decomposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photo-fixing type thermosensitive recording medium and a method for manufacturing the same.

[0002]

2. Description of the Related Art At present, a heat-sensitive recording medium (sometimes referred to as heat-sensitive recording paper) which is generally popular uses a leuco dye-based coloring material. One of the characteristics of such a thermal recording medium is that it does not require a developing / fixing process.

However, the feature that the developing / fixing process is unnecessary is a drawback that the image storability is insufficient. For example, if the white portion is intentionally or erroneously heated after thermal recording, the white portion is colored, and the recording may become unreadable or tampered with. For this reason,
Prevention of falsification by complete fixing is strongly demanded for recording media such as train tickets and commuter passes, which are similar to securities requiring immediate printing.

From such a background, in recent years, a photofixing type thermosensitive recording medium using a photodecomposable diazonium salt has been provided as a solution to the drawbacks of the thermosensitive recording medium using a leuco dye-based coloring material. ing. This heat-sensitive recording medium comprises a support and a color-forming layer containing a diazonium salt, a coupler, and a basic compound (sometimes referred to as an organic base or a basic organic substance). And
In order to achieve both good shell life and high thermal sensitivity,
It is known that the diazonium salt is microencapsulated, that is, the diazonium salt is encapsulated in the microcapsule.

Among such heat-sensitive recording media, those which develop red color are desired to be used for the printing portion of the imprint image. Further, in order to improve the recognizability of the printing of the imprint image and the visual inspection, there is a strong demand for a material capable of developing two colors of red and black.

By the way, in producing a photo-fixing type heat-sensitive recording medium in which a diazonium salt is microencapsulated, particularly in order to microencapsulate the diazonium salt, a diazonium salt that is poorly water-soluble and highly oil-soluble is used. It is dissolved in a high boiling point oil and microencapsulated. This microencapsulation emulsifies a core substance in which a diazonium salt, an oil, and a wall forming agent are dissolved, and then heats this to cause a polymerization reaction of an outer surface portion of oil droplets composed of the core substance, whereby a capsule wall is formed. To form. Then, a microazo-encapsulated diazonium salt, a coupler, and a basic compound are mixed and dispersed in a dispersion liquid to prepare a coating liquid for producing a thermal recording medium. A heat-sensitive recording medium is obtained by applying it to the support of 1 and drying it.

[0007]

However, as the photo-fixing type heat-sensitive recording medium using the photodecomposable diazonium salt, most of them develop blue, and few develop red.

Further, as a heat-sensitive recording medium capable of developing two colors of red and black, reference 1: "" 2-color emission type recording paper ", electrophotography, Vol. 26, No. 1, p26-30", reference 2 :
"TA System Direct Thermal Type Full Color Recording Material", Ja
pan Hardcopy ^, 94 Proce., p165-168 ", Document 3: JP-A-3-288688 and Document 4: JP-A-4-1988.
28585.

In Reference 1, a heat-sensitive recording medium for performing image recording by two-color development of red and black by using two kinds of diazonium salts and two kinds of couplers (referred to as a two-color emission type recording paper in Reference 1). ) Is disclosed. As the diazonium salt, a photodecomposable first diazonium salt having a maximum absorption at 400 nm and a non-photodecomposable second diazonium salt having a maximum absorption at 310 nm are used. As the coupler, a naphthol-based first coupler and an active methylene-based second coupler are used. In this case, the reaction between the first diazonium salt and the first coupler produces blue color, the reaction between the first diazonium salt and the second coupler produces yellow color, and the second diazonium salt and the first coupler produce It turns red when it reacts with the coupler. However, no color is developed in the reaction between the second diazonium salt and the second coupler. Therefore,
When this heat-sensitive recording medium is heated, the reaction between the first diazonium salt and the first and second couplers produces a green color, and the reaction between the second diazonium salt and the first and second couplers produces a red color. The color develops into black and appears black due to the mixture of green and red. After that, 42
When the first diazonium salt is photolyzed by irradiating it with light from a fluorescent lamp having an emission peak near 0 nm, the first diazonium salt loses its reactivity with the first and second couplers. After that, when the thermal recording medium is heated again, the reaction between the second diazonium salt and the first and second couplers causes red coloration. By the above operation, it is possible to record an image with two colors of red and black.

Further, in Documents 2 to 4, three color developing layers of cyan, yellow and magenta having different heat sensitivities are laminated on a support, and a heat resistant protective layer is provided on the uppermost layer to provide a full color image recording. A heat-sensitive recording medium (referred to as a heat-sensitive recording material in Documents 2 to 4) is disclosed. The yellow layer uses a diazonium salt that can be decomposed with 420 nm light as one of the coloring components, the magenta layer uses a diazonium salt that can be decomposed with 360 nm light as one of the coloring components, and the cyan layer has a basicity. Leuco dye is used as one of the coloring components. Then, writing of a yellow layer, fixing of the yellow layer by ultraviolet rays of 420 nm, writing of a magenta layer on this thermal recording medium, 365 nm
A full-color image recording can be performed by performing a series of processes of fixing the magenta layer with the ultraviolet rays and writing the cyan layer. However, in this case, the writing temperature increases in the order of writing the yellow layer, writing the magenta layer, and writing the cyan layer.

However, the above-mentioned literature 1 and literature 2
Even with the thermal recording media disclosed in Nos. 4 to 4, it was impossible to completely fix the image. Specifically, the thermosensitive recording medium disclosed in Document 1 cannot fix red color, and the thermal recording media disclosed in Documents 2 to 4 cannot fix the image in the cyan layer.

Further, in producing a light-fixing type heat-sensitive recording medium in which the above-mentioned diazonium salt is microencapsulated, microencapsulation of the diazonium salt is carried out.
Since it is usually carried out in a dispersion medium containing water, even if a diazonium salt having a low water solubility in the form of, for example, a tetrafluoroborate (BF ₄ ) salt or a hexafluorophosphate (PF ₆ ) salt is used, a part of it is water. It cannot prevent dissolution in the phase. Therefore, prepare (mix) the coating liquid
At that time, the diazonium salt dissolved in the aqueous phase reacts with the coupler, and a slight color development (precoupling) occurs. When a heat-sensitive recording medium is manufactured using the coating liquid that has already developed a color in this way, the obtained heat-sensitive recording medium has an increased optical density in the background portion, and good image recording (printing recording) cannot be obtained. Although the diazonium salt in the form of a tetraphenylborate (TPB) salt shows almost no water solubility, it cannot be used because it is thermally unstable.

Therefore, the advent of a photo-fixing type heat-sensitive recording medium that develops red color and a photo-fixing type thermosensitive recording medium that can develop two colors of red and black have been desired.

Further, a method of manufacturing a photo-fixing type heat-sensitive recording medium capable of reducing color development due to pre-coupling at the time of preparing a coating solution, thereby lowering the optical density of the background portion and obtaining good image recording. Appearance was desired.

[0015]

Therefore, according to the first photo-fixing type thermosensitive recording medium of the present invention, a coloring layer containing a diazonium salt encapsulated in microcapsules, a coupler and a basic compound is provided. In the provided light-fixing type heat-sensitive recording medium, a diazonium salt is added to 4-diazo-4'-n-butyldiphenylether salt (4-diazo-4'-n-butyl-dipheny
lether salt) and the coupler comprises a first coupler comprising naphthol AS and a naphthol AS-
And a second coupler composed of G.

Here, the diazonium salt includes tetrafluoroborate (BF ₄ ) salt, hexafluorophosphate (PF ₆ ) salt, and tetraphenylborate (TP).
B) It is desirable to use it in the form of salt.

When the light-fixing type heat-sensitive recording medium is constructed as described above, in order to record an image on the heat-sensitive recording medium and fix the recorded image, first, heat energy is applied to the heat-sensitive recording medium to form an image. Is recorded (sometimes referred to as thermal writing). In this case, the melt containing the first and second couplers and the basic compound obtained by applying thermal energy penetrates the microcapsules and reacts with the diazonium salt. The diazonium salt is
It reacts with the first coupler to develop a magenta color, and reacts with the second coupler to develop a yellow color. That is, since yellow and magenta colors are generated at the same time, the color is apparently red. Further, since the diazonium salt can be included in the microcapsule at a high concentration, the color density of the thermosensitive recording medium can be increased.

Thereafter, the thermosensitive recording medium is irradiated with light having a wavelength at which the diazonium salt can be decomposed. In this case, the unreacted diazonium salt absorbs this light and decomposes to lose its reactivity with the first and second couplers. As a result, even if thermal energy is applied thereafter, the color does not develop red, so that the red image is fixed.

Further, according to the second photo-fixing type thermosensitive recording medium of the present invention, the photo-fixing type thermosensitive recording comprising a color forming layer containing a diazonium salt encapsulated in microcapsules, a coupler and a basic compound. In the medium, the diazonium salt absorbs and decomposes a first diazonium salt that absorbs and decomposes a first light and a second light that does not decompose by the first light but has a shorter wavelength than the first light. A first diazonium salt, a coupler that reacts with the first diazonium salt to develop a blue color, and a second diazonium salt that reacts with a magenta color to form a first coupler; It is characterized by comprising a second coupler which reacts with a diazonium salt to develop a yellow color and which reacts with a second diazonium salt to develop a yellow color.

When the light-fixing type heat-sensitive recording medium is constructed as described above, in order to record an image on the heat-sensitive recording medium and fix the recorded image, first, heat energy is applied to the heat-sensitive recording medium to form an image. Record. In this case, the first and second obtained by applying thermal energy
The melt containing the coupler and the basic compound passes through the microcapsules and reacts with the first and second diazonium salts. The first diazonium salt reacts with the first coupler to develop a blue color, and reacts with the second coupler to develop a yellow color. Similarly, the second diazonium salt is
Reacts with the coupler (1) to develop magenta, and reacts with the second coupler to develop yellow. That is, since blue, yellow, and magenta colors are generated at the same time, the color is apparently black. This step is called the first thermal writing step.

Then, the thermosensitive recording medium is irradiated with the first light. In this case, the first diazonium salt that has not reacted in the first heat writing step absorbs the first light and decomposes to lose the reactivity with the first and second couplers. As a result, even if thermal energy is applied thereafter, the black color is not developed, so that the black image is fixed. This step is called the first fixing step.

After that, heat energy is applied to the thermosensitive recording medium to record an image. In this case, the second diazonium salt reacts with the first coupler to develop magenta, and reacts with the second coupler to develop yellow. That is, since yellow and magenta colors are generated at the same time, the color is apparently red. This step is called the second thermal writing step.

Then, the thermosensitive recording medium is irradiated with the second light having a shorter wavelength than the first light. In this case, the second diazonium salt that has not reacted in the first and second thermal writing steps absorbs the second light and decomposes to lose the reactivity with the first and second couplers. As a result,
Even if heat energy is applied, red color is not developed, so that a red image is fixed. This step is called the second fixing step.

As described above, the image recording and the fixing of the image by the two colors of red and black can be performed.

The wavelength of the first light is 410 ± 20.
It is preferable to use one having a wavelength of 365 nm and a wavelength of 365 ± 20 nm as the second light. This is because it is easy to obtain a light source having an emission wavelength center at 410 ± 20 nm and a light source having an emission wavelength center at 365 ± 20 nm. For example,
A fluorescent tube as a light source with an emission wavelength of 410 ± 20 nm,
That is, it is generally known that the tube is filled with mercury vapor and the inner wall of the tube is coated with a phosphor. Further, a fluorescent tube or a mercury lamp (g line) is known as a light source having an oscillation wavelength of 365 ± 20 nm.

The wavelength of the first light is 410 ± 2.
0 nm, the wavelength of the second light is 365 ± 20 nm
When the compounds described above are used, examples of the first and second diazonium salts and the first and second couplers shown below are given. As the first diazonium salt, 4- (4′-methylphenylthio) -2,5-
Diethoxybenzene diazonium salt (4- (4'-Methylphen
ylthio) -2,5-Diethoxybenzendiazonium Salt) (for example, DH575 (trade name) manufactured by Daito Chemix)
(See formula (1) below), 4-morpholino-2,5-
Dibutoxybenzene diazonium salt (4-Morpholino-2,5
-Dibutoxybenzendiazonium Salt) (for example, DH300 (trade name) manufactured by Daito Chemix Co., Ltd. (see the following formula (2))). In addition, as the second diazonium salt, Fast Red B (for example, Fast Red B BF ₄ Salt (trade name) manufactured by Aldrich) is used.
(Refer to formula (3) below)), Fast Red Viol
et LB (For example, Fast R manufactured by Aldrich
ed Violet LB Salt (trade name) (see formula (4) below), Fast Violet B (for example, manufactured by Aldrich, trade name is the same (see formula (5) below)), 4-diazo-4′-n -Butyl diphenyl ether salt (4-diazo-4'-n-butyl-diphenylether salt)
(See formula (6) below). These first and second diazonium salts are tetrafluoroborate (BF
₄ ) It is desirable to use it in the form of salt, hexafluorophosphate (PF ₆ ) salt, and tetraphenylborate (TPB) salt. Further, as the first coupler, naphthol AS (for example, manufactured by Kanto Chemical Co., Inc., trade name is the same (see formula (7) below)), naphthol AS-BO (for example, manufactured by Kanto Chemical Co., Ltd., trade name is the same (see below). (See formula (8))), Naphthol AS-D (for example, manufactured by Kanto Chemical Co., Inc., trade name is the same (see formula (9) below)), Naphthol AS-MX (for example, manufactured by Kanto Chemical Co., Ltd., trade name is the same). (See the following formula (10))), Naphthol AS-OL (for example, manufactured by Kanto Chemical Co., Inc., and have the same trade name (see the following formula (11))). Also, as a second coupler, Naphthol AS-G
(For example, the product name of Kanto Chemical Co., Ltd. is the same ((12) below)
Formula)), acetoacetoanilide (Acetoacetoanilid)
e) (see formula (13) below), 2-benzoylacetoanilide (see formula (14) below), and the like. In the formulas (1), (2), (5) and (6), X ⁻ represents a counter anion of the diazonium salt.

[0027]

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[0028]

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[0029]

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In the second photo-fixing type heat-sensitive recording medium of the present invention, the first diazonium salt is added to 4- (4'-
Methylphenylthio) -2,5-diethoxybenzenediazonium salt (4- (4'-Methylphenylthio) -2,5-Diethoxy
benzendiazonium salt), and the second diazonium salt is added to 4-diazo-4'-n-butyldiphenylether salt (4-diazo-4'-n-butyl-diphenylether Sal
t) and the first coupler is naphthol AS and the second coupler is naphthol AS-G, the second diazonium salt is highly incorporated into the microcapsules. It can be included in the concentration. Further, in this case, the absorption of the light emitted from the light source used in the first fixing step by the second diazonium salt is reduced, and as a result, the photodecomposition of the second diazonium salt during the first fixing is reduced. . Therefore, even if the ratio of the microcapsules containing the second diazonium salt is reduced, a sufficient red color density can be obtained.

Further, according to the third photo-fixing type thermosensitive recording medium of the present invention, the photo-fixing type thermosensitive recording comprising a coloring layer containing a diazonium salt encapsulated in microcapsules, a coupler and a basic compound. In the medium, the diazonium salt absorbs and decomposes a first diazonium salt that absorbs and decomposes a first light and a second light that does not decompose by the first light but has a shorter wavelength than the first light. A first diazonium salt, a coupler that reacts with the first diazonium salt to develop a blue color, and a second diazonium salt that reacts with a magenta color to form a first coupler; A second coupler which reacts with a diazonium salt to develop a yellow color and which reacts with a second diazonium salt to develop a yellow color, and a second coupler which reacts with a first diazonium salt to develop a red color and a second diazonium salt. When And respond, characterized in that consisted of a third coupler which develops a color to yellow.

When the light-fixing type heat-sensitive recording medium is constructed as described above, the first heat-writing step, the first heat-writing step, as in the case of recording and fixing an image on the second light-fixing type heat-sensitive recording medium of the present invention. Fixing step, second thermal writing step and second
By carrying out the fixing step, it is possible to perform image recording and fixing of the image by two colors of red and black. Here, in the first heat writing step, the first diazonium salt reacts with the first coupler to develop blue, reacts with the second coupler to develop yellow, and reacts with the third coupler. And develops red. Similarly, the second diazonium salt reacts with the first coupler to develop magenta, reacts with the second coupler to develop yellow, and reacts with the third coupler to develop yellow. That is, since blue, yellow, red, and magenta colors are simultaneously generated, the color is apparently black. In the second heat writing step, the second diazonium salt reacts with the first coupler to develop magenta, reacts with the second coupler to develop yellow, and reacts with the third coupler. Develops yellow. That is, since yellow and magenta colors are generated at the same time, the color is apparently red.

The wavelength of the first light is 410 ± 20.
It is preferable to use one having a wavelength of 365 nm and a wavelength of 365 ± 20 nm as the second light.

The wavelength of the first light is 410 ± 2.
0 nm, the wavelength of the second light is 365 ± 20 nm
When the compounds described above are used, examples of the first and second diazonium salts and the first to third couplers shown below are given. As the first diazonium salt, 4-morpholino-2,5-dibutoxybenzenediazonium salt (4-Morpholino-2,5-Dibutoxybenzendiazo
nium Salt) (for example, DH manufactured by Daito Chemix)
300 (trade name) (see the above formula (2)) and the like.
Further, as a second diazonium salt, Fast Red
B (For example, Fast Red manufactured by Aldrich
B BF ₄ Salt (trade name) (see the formula (3) above), Fast Red Violet LB (eg, Fast Red Violet manufactured by Aldrich Co., Ltd.)
t LB Salt (trade name) (see formula (4) above), Fast Violet B (for example, manufactured by Aldrich Co., trade name is the same (see formula (5) above)) and the like. The first and second diazonium salts are preferably used in the form of tetrafluoroborate (BF ₄ ) salt, hexafluorophosphate (PF ₆ ) salt, and tetraphenylborate (TPB) salt. Also, the first
As the coupler of Naphthol AS (for example, manufactured by Kanto Kagaku Co., Ltd., trade name is the same (see formula (7) above)), Naphthol AS-BO (for example, manufactured by Kanto Kagaku Co., trade name is the same (Formula (8) above) )), Naphthol AS-D (for example, manufactured by Kanto Chemical Co., Inc., the same trade name (see formula (9) above)), naphthol AS-MX (for example, manufactured by Kanto Chemical Co., Ltd., trade name is the same (refer to (10 above)). ) Formula))), Naphthol AS-OL (for example, manufactured by Kanto Chemical Co., Inc., having the same trade name (see formula (11) above)). Further, as the second coupler, naphthol AS-G (for example, manufactured by Kanto Chemical Co., Inc., having the same trade name (see the above formula (12))), acetoacetoanilide (Acetoacetoanilide) (the above (13))
Formula), 2-benzoylacetanilide (2-Benzoyla
cetoanilide) (see the above formula (14)). Also, as the third coupler 18c, 3-methyl-1-phenyl-5-pyrazolone (3-Methyl-1-Phenyl-5-Pylazo) is used.
lone) (see formula (15) below).

[0035]

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Further, according to the method for producing a light-fixing type thermosensitive recording medium of the present invention, a mixed dispersion liquid containing a diazonium salt encapsulated in microcapsules, a coupler and a basic compound is coated on a support. In the method for producing a photo-fixing type heat-sensitive recording medium which is then dried to produce a photo-fixing type thermosensitive recording medium, in producing a microcapsule containing a diazonium salt, first, the microcapsule wall is encapsulated with the diazonium salt. It is formed by an interfacial polymerization method in a water-existing liquid, and subsequently, a salt having a tetraphenylborate group is added to the water-existing liquid to form a water phase in the water-existing liquid until the microcapsule wall is formed. It is characterized in that only the diazonium salt dissolved therein is replaced with a tetraphenylborate salt, and then the tetraphenylborate salt is decomposed.

That is, in order to prevent pre-coupling that occurs when a coating solution is prepared, the method for producing a light-fixing type thermosensitive recording medium of the present invention comprises forming microcapsule walls by polymerization and then diazonium in the aqueous phase. The salt is thermally decomposed. More specifically, in order to thermally decompose the diazonium salt present in the aqueous phase, after the polymerization of the microcapsule wall is completed, for example, sodium tetraphenylborate (NaTPB) is used. Is added to change the diazonium salt existing in the aqueous phase into a tetraphenylborate (TPB) salt form.
The diazonium salt in the form of the tetraphenylborate (TPB) salt is thermally unstable as described above, and is decomposed even if stored at room temperature. However, this property is utilized here. , By heating a microcapsule solution of tetraphenylborate (TPB) salified from only the diazonium salt in the aqueous phase, only the diazonium salt in the aqueous phase is thermally decomposed, and the reaction with the coupler during preparation (mixing) of the coating solution is performed. It has lost sex.

In the case of producing a light-fixing type heat-sensitive recording medium in this manner, only the diazonium salt that has been transferred to the aqueous phase until the microcapsule wall is formed is a salt having a tetraphenylborate (TPB) group, Thus, for example, sodium tetraphenylborate (NaTPB) is added to a water-existing liquid to replace it with a thermally labile tetraphenylborate (TPB) salt, which is then obtained in order to decompose it. By using the microcapsules, it is possible to reduce the color development due to the reaction between the diazonium salt and the coupler when the coating solution is prepared.

Also, tetraphenyl borate (TPB)
If the diazonium salt substituted with the salt is decomposed by heating, the decomposition treatment time is shortened.

The diazonium salt used in the method for producing the photo-fixing type thermosensitive recording medium of the present invention is 4- (4 ').
-Methylphenylthio) -2,5-diethoxybenzenediazonium salt (4- (4'-Methylphenylthio) -2,5-Dietho
xybenzendiazonium Salt) (for example, DH575 (trade name) manufactured by Daito Chemix Co., Ltd. (see formula (1) above)), 4-morpholino-2,5-dibutoxybenzenediazonium salt (4-Morphorino-2,5-Dibutoxybenzend)
iazonium Salt) (for example, D manufactured by Daito Chemix)
H300 (trade name) (see formula (2) above), Fast
Red B (For example, Fast manufactured by Aldrich
Red B BF ₄ Salt (trade name) ((3) above)
(See formula)), Fast Red Violet LB
(For example, Fast Red B manufactured by Aldrich
Violet LB Salt (trade name) ((4) above)
Formula)), Fast Red B (for example, manufactured by Aldrich, the product name is the same (see Formula (5) above)), 4-
Diazo-4'-n-butyldiphenyl ether salt (4-di
azo-4'-n-butyl-diphenylether salt) (see the formula (6) above) and the like.

These diazonium salts are preferably used in the form of tetrafluoroborate (BF ₄ ) salt or hexafluorophosphate (PF ₆ ) salt in order to reduce the water solubility.

[0042]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. In each of the drawings used in the following description, each constituent component is merely a schematic representation of the shape, size, and arrangement relationship of each constituent component to the extent that the present invention can be understood. Further, in each of the drawings used for description, the same components are denoted by the same reference numerals. Further, hatching indicating a cross section is omitted except for a part. Numerical conditions such as materials used, forming method, and film thickness described in the following description are only preferable examples of the embodiment of the present invention. Therefore, it should be understood that the present invention is not limited to only these conditions.

1. First Embodiment FIG. 1 is a schematic sectional view showing an optical fixing type thermal recording medium of this embodiment. As shown in FIG. 1, the optical fixing type thermosensitive recording medium 100 of this embodiment is composed of a support 10 and a color-developing layer 12 provided thereon. The color forming layer 12 is formed of a binder resin 14 and components that contribute to color development, and each component is the binder resin 14
It is held in a uniformly dispersed state. Here, one type of diazonium salt 16 and one type of coupler 18 that reacts with the diazonium salt 16 to develop a desired color are used as main components that contribute to color development. The binder resin 14 used here is a polyvinyl alcohol resin. Further, the diazonium salt 16 has 4-
(4'-Methylphenylthio) -2,5-diethoxybenzenediazonium hexafluorophosphate (4-
(4'-Methylphenylthio) -2,5-Diethoxybenzendiazonium
Hexafluorophosphate (D manufactured by Daito Chemix Co., Ltd.
H575PF6 (trade name)), wavelength 410 ± 20
It absorbs nm light and decomposes it. The coupler 18 is Naphthol AS (for example, manufactured by Kanto Chemical Co., Inc., having the same trade name) and reacts with the diazonium salt 16 to develop a magenta color. And diazonium salt 1
The diazonium salt 16 is retained in the binder resin 14 in a microencapsulated state so that 6 and the coupler 18 do not react with each other. On the other hand, coupler 18
Are held in the binder resin 14 in the form of fine powder.

In addition to the diazonium salt 16 and the coupler 18, a sensitizer 22 for lowering the melting points of the basic compound 20 and the coupler 18 which accelerates the reaction between the diazonium salt 16 and the coupler 18 during image recording are each finely added. It is held in the binder resin 14 in the powder state.

The thermal recording medium 100 of this embodiment as described above was manufactured according to the following steps.

[1-1] Preparation of microcapsule solution of diazonium salt 4- (4'-methylphenylthio) -2,5-diethoxybenzenediazonium hexafluorophosphate (4- (4'-Methylphenylthio) as diazonium salt ) -2,5-
Diethoxybenzendiazonium Hexafluorophosphate) (Daito Chemix DH575PF6 (trade name))
(DH575PF6 (trade name) manufactured by Daito Chemix Co., Ltd.) 4 parts by weight, 48 parts by weight di-n-butyl phthalate, and D-110N (trade name) 4 manufactured by Takeda Pharmaceutical Co., Ltd. as a xylylene diisocyanate-based polyisocyanate.
8 parts by weight and 12 parts by weight of ethyl acetate were mixed and heated to 40 ° C. with uniform stirring to completely dissolve the diazonium salt. 8.2 of polyvinyl alcohol (N-300 (trade name) manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was added to the solution.
126 parts by weight of a wt% aqueous solution was added, and the mixture was emulsified and dispersed by a homogenizer. Further, 200 parts by weight of water is added to the obtained emulsion (emulsion dispersion) to homogenize it, and the mixture is heated with stirring at 60 ° C. for 3 hours to carry out an encapsulation reaction by an interfacial polymerization method to form a microcapsule wall. A microcapsule liquid (microcapsule dispersion liquid) of the diazonium salt was formed. The average particle size of the microcapsules was about 1 μm. The polyvinyl alcohol aqueous solution used here functions as an emulsion stabilizer and a protective colloid, and also functions as a binder resin after the coating film is formed. The same applies to the polyvinyl alcohol aqueous solution used in the following steps.

When the microcapsule wall is formed in this way, an oil phase (that is, a diazonium salt, di-n-butyl phthalate, D110N) is mixed between the time when the polyvinyl alcohol aqueous solution is charged and the time when the capsule wall is formed. Part of the diazonium salt dissolved in the (dissolved product), that is, the water-soluble one is transferred to the aqueous phase (that is, the polyvinyl alcohol aqueous solution).

[1-2] Tetraphenylborate (TPB) Chlorination and Thermal Decomposition of Diazonium Salt in Aqueous Phase The microcapsule solution prepared in the step [1-1] (that is, water-existing solution) was kept at 50 ° C. In this state, 1 part by weight of sodium tetraphenylborate was added and stirred for 1 hour. By this operation, the first diazonium salt dissolved in the aqueous phase of the microcapsule liquid and the first diazonium salt having an incomplete microcapsule wall are converted into tetraphenyl tetraphenyl from the form of hexafluorophosphate (PF ₆ ). It changed into the form of borate (TPB) salt. That is,
In the form of a hexafluorophosphate (PF ₆ ) salt, a diazonium salt, which is thermally stable but slightly soluble in water, is a thermally unstable tetraphenylborate (TPB) which is completely insoluble in water. It changed into salt form. The microcapsule solution was then left at room temperature to decompose the thermally unstable diazonium salt in the form of the tetraphenylborate (TPB) salt and lose its reactivity with the coupler.
Here, particularly when it is desired to accelerate the decomposition treatment, the microcapsule solution is heated to about the temperature at the time of microencapsulation described above, for example, about 40 to 60 ° C., and thereby the tetraphenylborate (TPB) salt is formed. The decomposition of the diazonium salt may be accelerated. By this decomposition treatment, the diazonium salt dissolved in the aqueous phase disappears almost completely in the microcapsule liquid, and only the diazonium salt in the oil phase encapsulated in the microcapsule exists.

[1-3] Preparation of coupler dispersion 10 parts by weight of naphthol AS (for example, manufactured by Kanto Kagaku Co., Ltd., having the same trade name) as a coupler was mixed with polyvinyl alcohol (N-300 manufactured by Nippon Synthetic Chemical Co., Ltd. (trade name). )) 5.0
Add wt% aqueous solution to 50 parts by weight and add 72 by ball mill.
Mixing and pulverization were carried out for a period of time to obtain a coupler dispersion. The average particle size of the coupler in the dispersion was about 1 μm.

[1-4] Preparation of basic compound dispersion 1,2,3-as a basic compound instead of the coupler
A dispersion liquid of a basic compound was obtained by the same method as in [1-3] except that triphenylguanidine was used. The average particle size of the basic organic substance in the dispersion was about 1 μm.

[1-5] Preparation of sensitizer dispersion A sensitizer was prepared in the same manner as in [1-3] except that benzyl 4-hydroxybenzoate was used as the sensitizer instead of the coupler. A sensitizer dispersion was obtained. The average particle size of the sensitizer in the dispersion was about 1 μm.

[1-6] Preparation of coating liquid The liquids prepared as described above were mixed in the following ratios,
The coating liquid was obtained by uniformly stirring. The mixing ratio of the microcapsule liquid and the coupler dispersion liquid is determined so that a desired color is produced. A microcapsule solution of the diazonium salt was used after the step [1-2], and a 10 wt% aqueous solution of sodium dodecylbenzenesulfonate aqueous solution was used as a surfactant to improve the coating property.

Microcapsule solution of diazonium salt 10 parts by weight Coupler dispersion 2 parts by weight Basic compound dispersion 2 parts by weight Sensitizer dispersion 10 parts by weight Surfactant 0.5 parts by weight.

[1-7] Coating The coating solution prepared in the step [1-6] was coated on a synthetic paper (SPU-110XEW (trade name) manufactured by Nisshinbo Co., Ltd.) with a bar coater (# 5 bar was used). , Dried at room temperature. The thickness of the coating film obtained after drying was about 10 μm. The thermal recording medium 100 was manufactured as described above.

Next, the surface reflection spectrum of the heat-sensitive recording medium 100 of this embodiment manufactured in this way is measured by the same method as that of the heat-sensitive recording medium 100 of this embodiment except the step [1-2]. Description will be made in comparison with the surface reflection spectrum of the conventional thermal recording medium manufactured by. In FIG. 2, the vertical axis represents the surface reflection spectrum (curve a in FIG. 2) of the thermal recording medium 100 of this embodiment and the surface reflection spectrum (curve b in FIG. 2) of the conventional thermal recording medium. (%), And the horizontal axis shows the wavelength (nm).

Curves a and b show a reflectance of about 10% when the wavelength is 300 nm. And the wavelength is 400n
After maintaining the reflectance of about 10% up to about m, the reflectance increases sharply when the wavelength becomes longer, and the wavelength becomes 500
In the case of nm, the reflectance is about 80%. As the wavelength becomes longer, the reflectance of curve a continues to increase slightly,
When the wavelength is 700 nm, the reflectance is about 90%. On the other hand, in the case of the curve b, the reflectance is once decreased and the wavelength is 600n.
After exhibiting a reflectivity of about 75% at m, the reflectivity rises, and at a wavelength of 700 nm, a reflectivity equivalent to that of the curve a is exhibited. From this, the thermal recording medium 1 of this embodiment is
It can be understood that in No. 00, a broad absorption peak centered at a wavelength of 600 nm due to the reaction between the diazonium salt and the coupler, which has occurred in the conventional thermal recording medium, does not occur, and the optical density of the background portion is lowered. That is, it can be understood that the color development due to the precoupling at the time of preparing the coating solution is reduced.

Therefore, in the manufacturing method shown in this embodiment, the color formation due to the pre-coupling at the time of preparing the coating solution is reduced, and the optical density of the background portion of the resulting heat-sensitive recording medium is lowered to achieve good image recording. Can be obtained.

2. Second Embodiment FIG. 3 is a schematic sectional view showing an optical fixing type thermosensitive recording medium of this embodiment. As shown in FIG. 3, the optical fixing type thermosensitive recording medium 200 of this embodiment has almost the same configuration as the thermosensitive recording medium 100 of the first embodiment, and therefore, in the following description, mainly the first type will be described. Differences from the thermal recording medium 100 of the embodiment will be described, and other detailed description will be omitted.

The thermal recording medium 200 of this embodiment uses one kind of diazonium salt 16 and two kinds of couplers as main components contributing to color development (hereinafter, one of the two kinds of couplers is used. Is referred to as the first coupler 18a, and the other is referred to as the second coupler). The diazonium salt 16 used here is 4-diazo-4'-n-butyldiphenyletherhexafluorophosphate (4-di
azo-4'-n-butyl-diphenylether Hexafluorophosphate)
And absorbs light having a wavelength of 365 ± 20 nm. The first coupler 18a is Naphthol AS (for example, manufactured by Kanto Chemical Co., Inc., having the same trade name) and reacts with the diazonium salt 16 to develop a magenta color.
The second coupler 18b is Naphthol AS-G (manufactured by Kanto Chemical Co., Inc., trade name is the same), and the diazonium salt 1 is used.
It reacts with 6b to develop a yellow color.

The thermal recording medium 200 of this embodiment as described above was manufactured according to the following steps.

[2-1] Preparation of microcapsule solution of diazonium salt 4-diazo-4'-n-butyldiphenyletherhexafluorophosphate (4-diazo salt as diazonium salt
azo-4'-n-butyl-diphenylether Hexafluorophosphate)
4 parts by weight, 48 parts by weight of di-n-butyl phthalate, and 48 parts by weight of D-110N (trade name) manufactured by Takeda Pharmaceutical Co., Ltd. as a xylylene diisocyanate-based polyisocyanate were mixed and stirred uniformly. The diazonium salt of 1 was completely dissolved. In this solution, polyvinyl alcohol (N-300 (trade name) manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
126 parts by weight of an 8.2 wt% aqueous solution of was added and emulsified and dispersed by a homogenizer. Further, 200 parts by weight of water is added to the obtained emulsion to homogenize it, and the mixture is stirred for 40 minutes.
The mixture was heated at 0 ° C. for 6 hours to carry out an encapsulation reaction by an interfacial polymerization method to form a microcapsule wall to obtain a microcapsule solution of diazonium salt. The average particle size of the microcapsules was about 1 μm.

Incidentally, an auxiliary solvent (ethyl acetate in this step) generally used for dissolving the diazonium salt in oil (di-n-butyl phthalate in this step).
As can be understood from the fact that is not used in this step, the diazonium salt is considered to be encapsulated in the microcapsules at a high concentration. That is, since it became possible to dissolve the diazonium salt in the oil without using an auxiliary solvent, it is considered that the diazonium salt is highly encapsulated in the microcapsules.

[2-2] Tetraphenylborate (TPB) Chlorination and Thermal Decomposition of Diazonium Salt in Aqueous Phase 40 The microcapsule solution prepared in the step [2-1] is used.
While maintaining the temperature at 0 ° C, 1 part by weight of sodium tetraphenylborate was added and stirred for 1 hour. By this operation, the diazonium salt dissolved in the aqueous phase of the microcapsule liquid and the diazonium salt having an incomplete microcapsule wall are converted from the hexafluorophosphate (PF ₆ ) salt form to the tetraphenylborate (TPB) salt. It changed into shape. That is, hexafluorophosphate (PF
₆ ) When in the salt form, the first diazonium salt, which is thermally stable but slightly soluble in water, is converted to a thermally unstable tetraphenylborate (TPB) salt which is completely insoluble in water. It changed into shape. Then, the microcapsule solution was heated to decompose the diazonium salt in the form of a tetraphenylborate (TPB) salt.

In addition, this [2-2] step is [2-1]
It is not necessary when the diazonium salt used in the process is in the form of tetraphenylborate (TPB) salt.

[2-3] Preparation of First Coupler Dispersion Liquid 10 parts by weight of naphthol AS (for example, manufactured by Kanto Chemical Co., Inc., having the same trade name) as the first coupler is polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Co., Ltd.). N-300 (trade name))
Was added to 50 parts by weight of a 5.0 wt% aqueous solution of and was mixed and pulverized with a ball mill for 72 hours to obtain a dispersion liquid of the first coupler. The average particle size of the first coupler in the dispersion was about 1 μm.

[2-4] Preparation of Second Coupler Dispersion Liquid In place of the first coupler, Naphthol AS-G (manufactured by Kanto Kagaku Co., trade name is the same) as the second coupler was used. Using the same method as in the step [2-3], a dispersion liquid of the second coupler was obtained. The average particle size of the second coupler in the dispersion was about 1 μm.

[2-5] Preparation of Basic Compound Dispersion Liquid A basic compound dispersion liquid was obtained by the same method as in the first embodiment.

[2-6] Preparation of Sensitizer Dispersion Liquid A sensitizer dispersion liquid was obtained in the same manner as in the first embodiment.

[2-7] Preparation of coating liquid The liquids prepared as described above were mixed in the following ratios,
The coating liquid was obtained by uniformly stirring. The mixing ratio of the microcapsule liquid and the coupler dispersion liquid is determined so that a desired color is produced. As the microcapsule solution of the diazonium salt, the one after the step [2-2] is used, and in order to reduce the background fog that occurs when the coating film is dried, an anionic silicone oil emulsion is prepared as Toray
Anionic silicone oil emulsion SM7001 manufactured by Dow Corning Silicone was used.

Microcapsule liquid of diazonium salt 10 parts by weight First coupler dispersion liquid 2.5 parts by weight Second coupler dispersion liquid 0.5 parts by weight Basic compound dispersion liquid 3 parts by weight Sensitizer dispersion liquid 6 parts by weight Silicone oil emulsion 2.0 parts by weight.

[2-8] Coating The coating solution prepared in the step [2-7] was coated on a synthetic paper (SPOY-140 (trade name) manufactured by Nisshinbo Co., Ltd.) with a bar coater (# 5
Of the bar) and dried at room temperature. The thickness of the coating film obtained after drying was about 10 μm. The thermal recording medium 200 was manufactured as described above.

Next, the color forming characteristics of the thermal recording medium 200 of this embodiment manufactured in this way will be described. A Macbeth reflection densitometer (RD-1200 (trade name) manufactured by Macbeth) was used for measuring the optical density.

Here, first, thermal writing was performed on the thermal recording medium 200 using a line thermal head (LH4115 (trade name) manufactured by TDK). The color tone obtained here was red. Further, the optical density is 0.7, and a thermal recording medium manufactured by the same method as this embodiment (using an auxiliary solvent for dissolving the diazonium salt in oil, except that another diazonium salt is used). It was confirmed that the color density was improved in comparison with the one used. It is considered that the color density was improved because the diazonium salt was contained in the microcapsules at a high concentration.

Next, 357n is applied to the thermosensitive recording medium 200.
Fluorescent tube that efficiently emits m light (U manufactured by Ushio Inc.
About 1 light of FL31140SCS-UV5 (trade name)
The diazonium salt was decomposed by irradiation for 40 seconds.

When the line thermal head (LH4115 (trade name) manufactured by TDK) was used to perform thermal writing on the thermosensitive recording medium 200 obtained by decomposing the diazonium salt, first and second couplers and a basic compound were obtained. Also, although a heating mark due to the difference in surface reflection due to the dissolution of the sensitizer was observed, coloration due to the reaction between the diazonium salt and the coupler was not observed.

From the above, it can be understood that the red coloring image can be completely fixed by performing the thermal writing and the diazonium salt.

The 4-diazo-4'-n-butyldiphenyletherhexafluorophosphate (4-diazo-4'-n-butyl-dip) used as the diazonium salt 16 was used.
henylether hexafluorophosphate) was synthesized according to the following steps.

<1> Synthesis of 4-nitro-4′-n-butyldiphenyl ether First, according to the reaction formula represented by the following formula (16), 4
-Nitro-4'-n-butyldiphenyl ether was synthesized.

[0079]

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18.6 g of n-butylphenol and 2 parts of p-bromonitrobenzene were added to 41 ml of dimethylformamide.
5.0 g and 17.2 g of potassium carbonate were added, respectively.
The mixture was reacted by stirring at 140 ° C. for 12 hours. After cooling the reaction solution to room temperature, the reaction solution was poured into 200 ml of water at normal temperature, and extracted twice with 100 ml of ethyl acetate. After washing the extract (that is, the ethyl acetate solution) with water, the extract was concentrated by evaporating the ethyl acetate as a solvent under reduced pressure. The extract was concentrated until ethyl acetate hardly evaporated. Then, the concentrated solution was developed with n-hexane by silica gel column chromatography to obtain 30.2 g of 4-nitro-4′-n-butyldiphenyl ether.

<2> Synthesis of 4-amino-4′-n-butyldiphenyl ether Then, according to the reaction formula represented by the following formula (17),
4-Amino-4′-n-butyldiphenyl ether was synthesized.

[0082]

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To 300 ml of dimethylformamide, 10 ml of concentrated hydrochloric acid (35 wt%; the same in the following steps), 20 g of iron powder and 45 ml of water were added, and the mixture was stirred at 95 ° C. for 1 hour, and then 4-nitro-4′-n-. Butyl diphenyl ether (30.2 g) was added, and the mixture was reacted by stirring at 95 ° C for 30 minutes. After cooling the reaction solution to room temperature, the reaction solution was filtered using filter paper, and the filtrate was concentrated by evaporating dimethylformamide as a solvent under reduced pressure. The filtrate was concentrated until almost no dimethylformamide was evaporated. After that, the concentrated liquid was added to water
0 ml was injected and extracted with 200 ml of ethyl acetate. The extract (ie, ethyl acetate solution) was washed with water and dried, and then ethyl acetate as a solvent was evaporated under reduced pressure to concentrate the extract. The extract was concentrated until ethyl acetate hardly evaporated. Thereafter, the precipitated crystals were separated by filtration using filter paper, washed with a small amount of ethyl acetate, and dried to obtain 25.4 g of 4-amino-4′-n-butyldiphenyl ether.

<3> Synthesis of 4-diazo-4′-n-butyldiphenyletherhexafluorophosphate Finally, according to the reaction formula represented by the following formula (18),
4-diazo-4'-n-butyldiphenyletherhexafluorophosphate was synthesized.

[0085]

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4-amino-4 'in 425 ml of methanol
Dissolving 25.4 g of n-butyldiphenyl ether;
After dropwise adding 69.1 g of concentrated hydrochloric acid, the mixture was further cooled to 38 watts under ice-cooling.
18.8 g of an aqueous solution of t% sodium nitrite was added dropwise,
The temperature was raised to ° C. and the mixture was stirred for 30 minutes to cause a diazotization reaction. Then, potassium hexafluorophosphate 2 was added to the reaction solution.
9.3 g was added and the mixture was stirred at 5 ° C. for 2 hours. Then, the precipitated crystals are filtered off using a filter paper, washed with water, and dried,
28.2 g of 4-diazo-4'-n-butyldiphenyletherhexafluorophosphate was obtained.

As described above, 4-diazo-4'-n
-Butyl diphenyl ether hexafluorophosphate was synthesized.

3. Third Embodiment FIG. 4 is a schematic sectional view showing a photo-fixing type thermosensitive recording medium of this embodiment. As shown in FIG. 4, the optical fixing type thermosensitive recording medium 300 of this embodiment is composed of a support 10 and a color-developing layer 12 provided thereon. The coloring layer 12 is formed of a binder resin 14 and components that contribute to two-color coloring, and each component is held in the binder resin 14 in a uniformly dispersed state. Here, two types of diazonium salts and two types of couplers that respectively react with the diazonium salts to develop a desired color are used as the main components contributing to the two-color development (hereinafter, referred to as two types of One of the diazonium salts is the first
And the other is referred to as the second diazonium salt 16b. Further, of the two types of couplers, one is referred to as a first coupler 18a and the other is referred to as a second coupler 18b. ). The binder resin 14 used here is a polyvinyl alcohol resin. The first diazonium salt 16a is 4- (4'-methylphenylthio) -2,5-diethoxybenzenediazonium hexafluorophosphate (4- (4'-Methylphenylthio)-
2,5-Diethoxybenzendiazonium Hexafluorophosphate)
(DH575PF6 (trade name) manufactured by Daito Chemix), which absorbs and decomposes the first light having a wavelength of 410 ± 20 nm. In addition, the second diazonium salt 16b is Fast Violet B (for example, manufactured by Aldrich Co., trade name is the same), which is not decomposed by the first light, but has a wavelength 365 ± 20 shorter than the first light.
It absorbs and decomposes the second light of nm. Also,
The first coupler 18a is Naphthol AS (for example, manufactured by Kanto Chemical Co., Inc., having the same trade name), reacts with the first diazonium salt 16a to develop a blue color, and reacts with the second diazonium salt 16b. It develops magenta.
The second coupler 18b is Naphthol AS-G (manufactured by Kanto Chemical Co., Inc., having the same trade name), reacts with the first diazonium salt 16a to develop a yellow color, and reacts with the second diazonium salt 16b. And develops a yellow color.
And the first and second diazonium salts 16a and 16b and the first and second couplers 18a and 18b.
The first and second diazonium salts 16a and 16b are retained in the binder resin 14 in a microencapsulated state so that they do not react with each other. On the other hand, the first and second couplers 18a and 18b are held in the binder resin 14 in the form of fine powder.

The first and second diazonium salts 1
6a and 16b and first and second couplers 18
In addition to a and 18b, a basic compound 20 and a first and second basic compound 20 which accelerates the reaction between the first and second diazonium salts 16a and 16b and the first and second couplers 18a and 18b during image recording. Coupler 18a
And a sensitizer 22 for lowering the melting point of 18b are held in the binder resin 14 in the form of fine powder.

The thermal recording medium 300 of this embodiment as described above was manufactured according to the following steps.

[3-1] Preparation of Microcapsule Solution of First Diazonium Salt 4- (4′-methylphenylthio) -2,5-diethoxybenzenediazonium hexafluorophosphate (4) as the first diazonium salt -(4'-Methylphenylthi
o) -2,5-Diethoxybenzendiazonium Hexafluorophosphate
) (Dai-Toke Mix DH575PF6 (trade name)) (Dai-Toke Mix DH575PF6
(Trade name) 4 parts by weight and di-n-butyl phthalate
48 parts by weight, 48 parts by weight of D-110N (trade name) manufactured by Takeda Pharmaceutical Co., Ltd. as a xylylene diisocyanate-based polyisocyanate, and 12 parts by weight of ethyl acetate were mixed and heated to 40 ° C. with uniform stirring. , The first diazonium salt was completely dissolved. To this solution, 126 parts by weight of an 8.2 wt% aqueous solution of polyvinyl alcohol (N-300 (trade name) manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was added and emulsified and dispersed by a homogenizer. Further, 200 parts by weight of water was added to the obtained emulsion to homogenize it, and the mixture was heated at 60 ° C. for 3 hours with stirring to carry out an encapsulation reaction by an interfacial polymerization method to form a microcapsule wall. A microcapsule solution of the diazonium salt of was obtained. The average particle size of the microcapsules was about 1 μm.

[3-2] Tetraphenylborate (TPB) Chlorination and Thermal Decomposition of the First Diazonium Salt in the Aqueous Phase 50 The microcapsule solution prepared in the step [3-1] is used.
While maintaining the temperature at 0 ° C, 1 part by weight of sodium tetraphenylborate was added and stirred for 1 hour. By this operation, the first diazonium salt dissolved in the aqueous phase of the microcapsule liquid and the first diazonium salt having an incomplete microcapsule wall are converted into tetraphenyl tetraphenyl from the form of hexafluorophosphate (PF ₆ ). Borate (TP
B) Change to salt form. That is, when in the form of a hexafluorophosphate (PF ₆ ) salt, the first diazonium salt, which was thermally stable but had some water solubility, was not stable at all, and the first diazonium salt had no water solubility. It was converted to the phenylborate (TPB) salt form. Then, by heating the microcapsule liquid, tetraphenyl borate (T
The first diazonium salt in the form of the PB) salt was decomposed.

In addition, this [3-2] step is performed by [3-1]
Not required if the first diazonium salt used in the process is in the form of a tetraphenylborate (TPB) salt.

[3-3] Preparation of Microcapsule Liquid of Second Diazonium Salt Instead of the first diazonium salt, Fast Violet B (for example, manufactured by Aldrich, trade name is the same) as the second diazonium salt was used. A microcapsule solution of the second diazonium salt was obtained in the same manner as in step [3-1], except that the encapsulation reaction was carried out at 40 ° C. using a tetraphenylborate (TPB) salt. The average particle size of the microcapsules was about 1 μm.

[3-4] Preparation of First Coupler Dispersion Liquid Naphthol AS (for example, manufactured by Kanto Chemical Co., Inc., trade name is the same) as 10% by weight of polyvinyl alcohol (manufactured by Nippon Synthetic Chemical Co., Ltd.) N-300 (trade name))
Was added to 50 parts by weight of a 5.0 wt% aqueous solution of and was mixed and pulverized with a ball mill for 72 hours to obtain a dispersion liquid of the first coupler. The average particle size of the first coupler in the dispersion was about 1 μm.

[3-5] Preparation of second coupler dispersion A naphthol AS-G (manufactured by Kanto Kagaku Co., trade name is the same) as the second coupler was used instead of the first coupler. Using the same method as in the step [3-4], a dispersion liquid of the second coupler was obtained. The average particle size of the second coupler in the dispersion was about 1 μm.

[3-6] Preparation of Basic Compound Dispersion Liquid A basic compound dispersion liquid was obtained by the same method as in the first embodiment.

[3-7] Preparation of Sensitizer Dispersion Liquid A sensitizer dispersion liquid was obtained by the same method as in the first embodiment.

[3-8] Preparation of coating liquids The liquids prepared as described above were mixed in the following ratios,
The coating liquid was obtained by uniformly stirring. The mixing ratio of the microcapsule liquid and the coupler dispersion liquid is determined so that a desired color is produced. A microcapsule solution of the first diazonium salt was used after the step [3-2], and a 10 wt% aqueous solution of sodium dodecylbenzenesulfonate was used as a surfactant to improve the coating property.

First diazonium salt microcapsule solution 5 parts by weight Second diazonium salt microcapsule solution 5 parts by weight First coupler dispersion 1 part by weight Second coupler dispersion 1 part by weight Basic compound dispersion 2 parts by weight Sensitizer dispersion 10 parts by weight Surfactant 0.5 parts by weight.

[3-9] Coating The coating solution prepared in the step [3-8] was coated on a synthetic paper (SPU-110XEW (trade name) manufactured by Nisshinbo Co., Ltd.) with a bar coater (# 5 bar was used). , Dried at room temperature. The thickness of the coating film obtained after drying was about 10 μm. The thermal recording medium 300 was manufactured as described above.

Next, the color forming characteristics of the heat-sensitive recording medium 300 of this embodiment manufactured in this way will be described. In FIG. 5, the color development characteristics of the heat-sensitive recording medium 300 of this embodiment are plotted on the vertical axis, and the optical density (Optical Dens) is plotted.
, and the temperature is plotted on the horizontal axis. In addition, Table 1 shows the measurement results at that time. In addition,
For the measurement of the color development characteristics, a thermal stamp method was used in which a metal block having a predetermined temperature was pressed against a thermosensitive recording medium to develop a color, and the color development portion was measured using a Macbeth reflection densitometer.

[0103]

[Table 1]

Here, first, a metal block having a predetermined temperature was pressed against the heat-sensitive recording medium 300 to perform the first heat writing, and then the color development characteristics were measured. The color tone obtained here is black, and its color development characteristics are indicated by black circles in FIG. FIG.
And, as shown in Table 1, the optical density when the thermal writing is performed at a temperature of 75 ° C. or less is 0.13 or less,
Optical density is 0.74 when thermal writing is performed at the temperature
Therefore, it is considered that color development has started between 75 ° C and 80 ° C. Further, since the optical density when the thermal writing is performed at a temperature of 100 ° C. or higher is almost constant, it is considered that the color development is saturated between 100 ° C. and 110 ° C.

Next, 400 n of the heat-sensitive recording medium 300 is added.
The first fixing is performed by irradiating the light of a fluorescent lamp for diazo copying (FL10BA37 (trade name) manufactured by Mitsubishi Electric Corporation) that efficiently emits m light for about 15 seconds to decompose the first diazonium salt. It was

Next, a metal block having a predetermined temperature was pressed against the heat-sensitive recording medium 300 in which the first diazonium salt was decomposed to carry out the second heat writing, and then the color development characteristics were measured. The color tone obtained here is red, and its color development characteristics are indicated by white circles in FIG. As shown in FIG. 5 and Table 1, the optical density when the thermal writing is performed at a temperature of 79 ° C. or lower is 0.12 or less, and the optical density when the thermal writing is performed at a temperature of 86 ° C. is 0.12 or less. 8 because it is 32
It is considered that color development started between 0 ° C and 85 ° C. Further, since the optical density when the thermal writing is performed at a temperature of 100 ° C. or higher is almost constant, it is considered that the color development is saturated between 100 ° C. and 110 ° C.

Further, the thermal recording medium 300 has 352
The second fixing is performed by irradiating the light of a black light blue fluorescent tube (FL10BLB (trade name) manufactured by Mitsubishi Electric Corp.) that efficiently emits light of nm for about 15 seconds to decompose the first diazonium salt. It was

When thermal writing is performed on the thermosensitive recording medium 300 obtained by decomposing the first and second diazonium salts by the heat stamp method, the first and second couplers, the basic compound and the sensitizer are dissolved. Although a heating mark due to a difference in surface reflection was observed, coloration due to a reaction between the diazonium salt and the coupler was not observed.

From the above, it can be understood that by performing thermal writing and decomposition of the diazonium salt alternately, it is possible to completely fix the two-color developed image of red and black. Also,
Since the color forming layer has a single layer structure, it is the easiest to form.

4. Fourth Embodiment A light-fixing type heat-sensitive recording medium according to this embodiment uses Fast Red B, Fast R as the second diazonium salt.
ed Violet LB or FastViole
In order to solve the dissatisfaction point when using t B, the second
4-diazo-4'-n-butyldiphenyl ether hexafluorophosphate (4-diazonium salt)
azo-4'-n-butyl-diphenylether Hexafluorophosphate)
The configuration is the same as that of the third embodiment except that is used.

The dissatisfaction point here is Fast Red.
When B, Fast Red Violet LB, or Fast Violet B is used as the second diazonium salt, Fast Red B, Fast
Red Violet LB and Fast Vi
Olet B absorbs the light emitted from the light source used in the first fixing step (hereinafter, sometimes referred to as the first fixing light source), and as a result, the second diazonium salt is absorbed to some extent during the first fixing step. Is to photodecompose.

On the other hand, when 4-diazo-4'-n-butyldiphenylether salt is used as the second diazonium salt, absorption of the light emitted from the first fixing light source is reduced, and as a result, Photodecomposition of the second diazonium salt during fixing of No. 1 is reduced.

FIG. 6 shows Fast Red B (curve a in FIG. 6) and Fast Red Violet LB.
(Curve b in FIG. 6), Fast Violet B (curve c in FIG. 6) and the absorbance spectrum of 4-diazo-4′-n-butyldiphenylether salt (curve d in FIG. 6) are plotted on the vertical axis. (Arbitrary unit) is taken, and the horizontal axis shows the wavelength (nm). However, all the diazonium salts used for measuring the absorbance spectrum are in the form of hexafluorophosphate (PF ₆ ) salts. Further, in FIG. 7, the first fixing light source, for example, the emission spectrum of UFL31140SCS-UV2 (trade name) manufactured by Ushio Inc. is plotted on the vertical axis for light intensity (arbitrary unit), and the horizontal axis for wavelength (nm). Is taken and shown.

A curve a in FIG. 6 shows an absorbance of about 0.9 when the wavelength is about 310 nm. After that, when the wavelength becomes longer, the absorbance decreases, and when the wavelength is about 320 nm, 0.7
After exhibiting an absorbance of about a certain degree, the absorbance again increases, and exhibits an absorbance of about 1.0 when the wavelength is about 375 nm. After that, as the wavelength becomes longer, the absorbance decreases and the wavelength becomes 4
When it is 00 nm, it shows an absorbance of about 0.6 and the wavelength is 50
The absorbance is about 0 at 0 nm.

The curve b is 0 .. when the wavelength is 300 nm.
It shows an absorbance of about 5. After that, when the wavelength becomes longer, the absorbance increases, and when the wavelength is about 350 nm, the absorbance is about 1.0. After that, when the wavelength becomes longer, the absorbance decreases, and when the wavelength is 375 nm, the absorbance is about 0.3, and when the wavelength is 400 nm, the absorbance is about 0.1. After that, after maintaining the absorbance of about 0.1 until the wavelength reaches about 450 nm, the absorbance decreases as the wavelength further increases, and the absorbance shows about 0 when the wavelength is 500 nm.

The curve c shows that when the wavelength is 300 nm,
The absorbance is about 3. After that, when the wavelength becomes longer, the absorbance increases, and when the wavelength is about 350 nm, the absorbance is about 1.0. After that, when the wavelength is further increased, the absorbance is decreased. When the wavelength is 375 nm, the absorbance is about 0.4, when the wavelength is 400 nm, the absorbance is about 0.1, and when the wavelength is 500 nm, the absorbance is about 0. Show.

The curve d is 1. when the wavelength is about 310 nm.
The absorbance is about 0. After that, when the wavelength becomes longer, the absorbance decreases and shows an absorbance of about 0.05 when the wavelength is 375 nm, an even smaller absorbance when the wavelength is 400 nm, and an absorbance of about 0 when the wavelength is 450 nm.

The emission spectrum of the first fixing light source shown in FIG. 7 shows that the light intensity is about 0 when the wavelength is 375 nm. After that, when the wavelength becomes longer, the light intensity increases and the wavelength becomes 400n.
It shows a light intensity of about 50 at m, and 2 at 420 nm.
The light intensity is about 75. After that, when the wavelength becomes longer, the light intensity decreases, and when the wavelength is 450 nm, the light intensity is about 50, and when the wavelength is 500 nm, the light intensity is about 0.
Is shown.

As described above, the absorbance spectra of the curves a to d and the emission spectrum of the first fixing light source have wavelengths of 375 n.
Although it overlaps in a region larger than m, the absorbance spectrum of the curve d is the first as compared with the absorbance spectrum of the curves ac.
Overlap with the emission spectrum of the fixing light source is reduced. From this fact, when 4-diazo-4′-n-butyldiphenylether salt is used as the second diazonium salt, absorption of light emitted from the first fixing light source is reduced, and as a result, the first fixing light source is fixed. It can be seen that the photolysis of the second diazonium salt is reduced over time.

FL10BA37 manufactured by Mitsubishi Electric Corporation
Even when (brand name) is used as the first fixing light source, the same effect as described above can be obtained.

The thermal recording medium of this embodiment as described above was manufactured according to the following steps.

[4-1] Preparation of Microcapsule Solution of First Diazonium Salt A microcapsule solution of the first diazonium salt was obtained by the same method as in the third embodiment.

[4-2] Tetraphenylborate (TPB) salinization and thermal decomposition of the first diazonium salt in the aqueous phase The first diazonium salt in the aqueous phase is prepared by the same method as in the third embodiment. Was subjected to tetraphenylborate (TPB) chlorination and pyrolysis.

[4-3] Preparation of microcapsule solution of second diazonium salt 4-diazo-4′-n-as second diazonium salt
Butyl diphenyl ether hexafluorophosphate (4-diazo-4'-n-butyl-diphenylether Hexafluorophosp
hate) 4 parts by weight, di-n-butyl phthalate 48 parts by weight and xylylene diisocyanate-based polyisocyanate manufactured by Takeda Pharmaceutical Co., Ltd. D-110N (trade name) 4
8 parts by weight were mixed, and the first diazonium salt was completely dissolved while stirring uniformly. To this solution, 126 parts by weight of an 8.2 wt% aqueous solution of polyvinyl alcohol (N-300 (trade name) manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was added and emulsified and dispersed by a homogenizer. Further, 200 parts by weight of water is added to the obtained emulsion to homogenize it, and the mixture is heated at 40 ° C. for 6 hours with stirring to carry out an encapsulation reaction by an interfacial polymerization method to form a microcapsule wall to form a diazonium salt. A microcapsule liquid of The average particle size of the microcapsules was about 1 μm.

Incidentally, an auxiliary solvent (ethyl acetate in this step) generally used for dissolving the diazonium salt in oil (di-n-butyl phthalate in this step).
As can be understood from the fact that is not used in this step, it is considered that the second diazonium salt is encapsulated in the microcapsules at a high concentration. That is,
It is considered that the diazonium salt is highly encapsulated in the microcapsules even without using an auxiliary solvent.

[4-4] Tetraphenylborate (TPB) salinization and thermal decomposition of the second diazonium salt in the aqueous phase. The microcapsule solution prepared in the step [4-3]
While maintaining the temperature at 0 ° C, 1 part by weight of sodium tetraphenylborate was added and stirred for 1 hour. By this operation, the second diazonium salt dissolved in the aqueous phase of the microcapsule liquid and the first diazonium salt having an incomplete microcapsule wall are converted into tetraphenyl tetraphenyl from the hexafluorophosphate (PF ₆ ) salt form. Borate (TP
B) Change to salt form. That is, in the hexafluorophosphate (PF ₆ ) salt form, the second diazonium salt, which was thermally stable but slightly soluble in water, was replaced by a thermally unstable tetrazine salt which was completely insoluble in water. It was converted to the phenylborate (TPB) salt form. Then, by heating the microcapsule liquid, tetraphenyl borate (T
The second diazonium salt in the form of the PB) salt was decomposed.

Incidentally, this [4-4] step is performed by [4-3]
Not required if the second diazonium salt used in the process is in the form of a tetraphenylborate (TPB) salt.

[4-5] Preparation of First Coupler Dispersion Liquid A first coupler dispersion liquid was obtained by the same method as in the third embodiment.

[4-6] Preparation of Second Coupler Dispersion Liquid A second coupler dispersion liquid was obtained in the same manner as in the third embodiment.

[4-7] Preparation of Basic Compound Dispersion Liquid A basic compound dispersion liquid was obtained by the same method as in the first embodiment.

[4-8] Preparation of Sensitizer Dispersion Liquid A sensitizer dispersion liquid was obtained in the same manner as in the first embodiment.

[4-9] Preparation of coating liquid The liquids prepared as described above were mixed in the following ratios,
The coating liquid was obtained by uniformly stirring. The mixing ratio of the microcapsule liquid and the coupler dispersion liquid is determined so that a desired color is produced. In addition, as the microcapsule liquid of the first and second diazonium salts, [4-2] and [4-
4] Use the one after the process, and use the anionic silicone oil emulsion SM7001 manufactured by Toray Dow Corning Silicone Co., Ltd. as the anionic silicone oil emulsion in order to reduce the background fog that occurs when the coating film is dried. I was there. Further, the ratio of the microcapsule liquid of the second diazonium salt when preparing the coating liquid is lowered as compared with the case of the third embodiment and the case of the fifth embodiment described later, while the first By increasing the ratio of the microcapsule liquid of the diazonium salt compared with the case of the third embodiment and the case of the fifth embodiment described later,
The total ratio of the microcapsule liquid of the first diazonium salt and the microcapsule liquid of the second diazonium salt is made substantially equal.

Microcapsule solution of first diazonium salt 8 parts by weight Microcapsule solution of second diazonium salt 2 parts by weight First coupler dispersion 2.5 parts by weight Second coupler dispersion 0.5 parts by weight Base 3% by weight of the compound dispersion, 6 parts by weight of the sensitizer dispersion, 2 parts by weight of the silicone oil emulsion.

[4-10] Coating The coating solution prepared in the step [4-9] was coated on a synthetic paper (SPU-110XEW (trade name) manufactured by Nisshinbo Co., Ltd.) with a bar coater (# 5 bar was used). , Dried at room temperature. The thickness of the coating film obtained after drying was about 10 μm. A thermal recording medium was manufactured as described above.

Next, the color forming characteristics of the heat-sensitive recording medium of this embodiment manufactured in this way will be described. A Macbeth reflection densitometer (RD-1200 (trade name) manufactured by Macbeth) was used for measuring the optical density.

First, a line thermal head (LH41 manufactured by TDK Co., Ltd. was used as the thermal recording medium of this embodiment.
15 (trade name)) was used for the first thermal writing.
The color tone obtained here was black. The optical density was 0.9.

Next, a fluorescent lamp (UFL3 manufactured by Ushio Inc.) that efficiently emits light of 420 nm is formed on the thermosensitive recording medium.
The first fixing was performed by irradiating with light of 1140 SCS-UV2) for about 15 seconds to decompose the first diazonium salt.

Second thermal writing was performed on the thermal recording medium obtained by decomposing the first diazonium salt by using a line thermal head (LH4115 (trade name) manufactured by TDK). The color tone obtained here was red. Further, the optical density was 0.3, and it was confirmed that a sufficient color density was obtained even though the ratio of the microcapsule solution of the second diazonium salt was reduced when preparing the coating solution. One reason why such a sufficient color density is obtained is that the second diazonium salt is contained in the microcapsules at a high density. Another reason is that the absorption of the second diazonium salt for light having a wavelength larger than 400 nm is reduced, and as a result, the second diazonium salt is decomposed by the light of the fluorescent lamp used for the first fixing. It is thought that this is due to a decrease in

Further, a fluorescent lamp (UFL manufactured by Ushio Inc.) that efficiently emits light of 357 nm is formed on the thermosensitive recording medium.
31140 SCS-UV5 (trade name) light about 140
A second fixing was carried out by decomposing the second diazonium salt by irradiation for a second.

For the thermal recording medium obtained by decomposing the first and second diazonium salts, a line thermal head (T
When heat writing is performed using LH4115 (trade name) manufactured by DK, although a heating mark due to a difference in surface reflection due to dissolution of the first and second couplers, the basic compound and the sensitizer is observed. No color development due to the reaction between the diazonium salt and the coupler was observed.

From the above, it can be understood that by performing thermal writing and decomposition of the diazonium salt alternately, it is possible to completely fix the two-color image of red and black. Also,
Since the color forming layer has a single layer structure, it is the easiest to form.
In addition, since the ratio of the microcapsule liquid of the first diazonium salt was increased by the amount of decreasing the ratio of the microcapsule liquid of the second diazonium salt when preparing the coating liquid,
The color tone of the first thermal writing was improved.

5. Fifth Embodiment FIG. 8 is a sectional view schematically showing a photo-fixing type thermal recording medium of this embodiment. As shown in FIG. 8, the optical fixing type heat-sensitive recording medium 500 of this embodiment has almost the same structure as the heat-sensitive recording medium 300 of the third embodiment. Differences from the thermal recording medium 300 of the embodiment will be described, and other detailed description will be omitted.

The thermal recording medium 500 of this embodiment uses two kinds of diazonium salts and three kinds of couplers as the main components contributing to the two-color development (hereinafter, one of the diazonium salts will be used). First diazonium salt 16
and the other is called the second diazonium salt 16b. In addition, three types of couplers are respectively used as the first coupler 18a, the second coupler 18b, and the third coupler 1.
8c. ). The first diazonium salt used here is 4-morpholino-2,5-dibutoxybenzenediazonium hexafluorophosphate (4-Morpholino-
2,5-Dibutoxybenzendiazonium Hexafluorophosphate)
(DH300PF6 (trade name) manufactured by Daito Chemix), which absorbs and decomposes the first light having a wavelength of 410 ± 20 nm. In addition, the second diazonium salt 16b is Fast Violet B (for example, manufactured by Aldrich Co., trade name is the same), which is not decomposed by the first light, but has a wavelength 365 ± 20 shorter than the first light.
It absorbs and decomposes the second light of nm. Also,
The first coupler 18a is Naphthol AS (for example, manufactured by Kanto Chemical Co., Inc., having the same trade name), reacts with the first diazonium salt 16a to develop a blue color, and reacts with the second diazonium salt 16b. It develops magenta.
The second coupler 18b is Naphthol AS-G (manufactured by Kanto Chemical Co., Inc., having the same trade name), reacts with the first diazonium salt 16a to develop a yellow color, and reacts with the second diazonium salt 16b. And develops a yellow color.
The third coupler is 3-methyl-1-phenyl-5.
-Pyrazolone (3-Methyl-1-Phenyl-5-Pylazolone), which reacts with the first diazonium salt 16a to give a red color and reacts with the second diazonium salt 18b to give a yellow color. is there.

The thermal recording medium 500 of this embodiment as described above was manufactured according to the following steps.

[5-1] Preparation of Microcapsule Solution of First Diazonium Salt 4-morpholino-2 as the first diazonium salt,
5-Dibutoxybenzenediazonium hexafluorophosphate (4-Morpholino-2,5-Dibutoxybenzendiazoni
um Hexafluorophosphate) (DH300PF6 (trade name) manufactured by Daito Chemix Co., Ltd.) 4 parts by weight, 48 parts by weight of di-n-butyl phthalate, and D- manufactured by Takeda Pharmaceutical Co., Ltd. as xylylene diisocyanate polyisocyanate.
48 parts by weight of 110N (trade name) and 12 parts of ethyl acetate
Part by weight was mixed and heated to 40 ° C. with uniform stirring to completely dissolve the first diazonium salt. In this solution, polyvinyl alcohol (N
126 parts by weight of 8.2 wt% aqueous solution of -300 (trade name) was added and emulsified and dispersed by a homogenizer. Further, 200 parts by weight of water was added to the obtained emulsion to homogenize it, and the mixture was heated at 60 ° C. for 3 hours with stirring to carry out an encapsulation reaction by an interfacial polymerization method to form a microcapsule wall. A microcapsule solution of the diazonium salt of was obtained. The average particle size of the microcapsules was about 1 μm.

[5-2] Tetraphenylborate (TPB) chlorination and thermal decomposition of the first diazonium salt in the aqueous phase. The microcapsule solution prepared in the step [5-1]
While maintaining the temperature at 0 ° C, 1 part by weight of sodium tetraphenylborate was added and stirred for 1 hour. By this operation, the first diazonium salt dissolved in the aqueous phase of the microcapsule liquid and the first diazonium salt having an incomplete microcapsule wall are converted into tetraphenyl tetraphenyl from the form of hexafluorophosphate (PF ₆ ). Borate (TP
B) Change to salt form. That is, when in the form of a hexafluorophosphate (PF ₆ ) salt, the first diazonium salt, which was thermally stable but had some water solubility, was not stable at all, and the first diazonium salt had no water solubility. It was converted to the phenylborate (TPB) salt form. Then, by heating the microcapsule liquid, tetraphenyl borate (T
The first diazonium salt in the form of the PB) salt was decomposed.

Incidentally, this [5-2] step is performed by [5-1]
Not required if the first diazonium salt used in the process is in the form of a tetraphenylborate (TPB) salt.

[5-3] Preparation of Microcapsule Solution of Second Diazonium Salt A second microcapsule solution of diazonium salt was obtained by the same method as in the third embodiment.

[5-4] Preparation of First Coupler Dispersion Liquid A first coupler dispersion liquid was obtained in the same manner as in the third embodiment.

[5-5] Preparation of Second Coupler Dispersion Liquid A second coupler dispersion liquid was obtained by the same method as in the third embodiment.

[5-6] Preparation of Third Coupler Dispersion Liquid 3-Methyl-1-phenyl-5 as Third Coupler
-Pyrazolone (3-Methyl-1-Phenyl-5-Pylazolone) 1
0 part by weight was added to 50 parts by weight of a 5.0 wt% aqueous solution of polyvinyl alcohol (N-300 (trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), and the mixture was pulverized and pulverized for 72 hours in a ball mill to prepare a third coupler. A dispersion was obtained. The average particle size of the third coupler in the dispersion was about 1 μm.

[5-7] Preparation of Basic Compound Dispersion Liquid A basic compound dispersion liquid was obtained by the same method as in the first embodiment.

[5-8] Preparation of Sensitizer Dispersion Liquid A sensitizer dispersion liquid was obtained by the same method as in the first embodiment.

[5-9] Preparation of coating liquid The liquids prepared as described above were mixed in the following ratios,
The coating liquid was obtained by uniformly stirring. The mixing ratio of the microcapsule liquid and the coupler dispersion liquid is determined so that a desired color is produced. A microcapsule solution of the first diazonium salt was used after the step [5-2], and a 10 wt% aqueous solution of sodium dodecylbenzenesulfonate was used as a surfactant to improve the coating property.

First diazonium salt microcapsule solution 5 parts by weight Second diazonium salt microcapsule solution 5 parts by weight First coupler dispersion 1 part by weight Second coupler dispersion 0.5 parts by weight Third Coupler dispersion 0.5 parts by weight Basic organic substance dispersion 1.5 parts by weight Sensitizer dispersion 9 parts by weight Surfactant 0.5 parts by weight.

[5-10] Coating The coating solution prepared in the step [5-9] was coated on a synthetic paper (SPU-110XEW (trade name) manufactured by Nisshinbo Co., Ltd.) with a bar coater (# 5 bar was used). , Dried at room temperature. The thickness of the coating film obtained after drying was about 10 μm. The thermal recording medium 500 was manufactured as described above.

Next, the color forming characteristics of the heat-sensitive recording medium 500 of this embodiment manufactured as described above will be described. In FIG. 9, the color development characteristics of the thermosensitive recording medium 500 of this embodiment are plotted on the vertical axis, and the optical density (Optical Dens) is plotted.
, and the temperature is plotted on the horizontal axis. The color development characteristics were measured by the same method as in the third embodiment.

As shown in FIG. 9, the color forming characteristics of the thermal recording medium 500 of this embodiment are almost the same as those of the thermal recording medium 300 of the third embodiment, and the first thermal writing is performed. The black color tone (shown by the black circles in FIG. 9) obtained after the color development is between 75 ° C. and 80 ° C.
It is considered that the color development is saturated between 00 ° C and 110 ° C. Further, the red color tone (shown by the white circle in FIG. 9) obtained after the second thermal writing develops between 80 ° C. and 85 ° C., and between 100 ° C. and 110 ° C. I think that the color is saturated.

Further, when writing is performed on the thermal recording medium 500 obtained by decomposing the first and second diazonium salts by the heat stamp method, the first, second and third couplers, the basic organic substance and the additional organic substance are added. Although a heating mark due to a difference in surface reflection due to dissolution of the sensitizer was observed, coloration due to a reaction between the diazonium salt and the coupler was not observed.

From the above, it can be understood that by performing thermal writing and decomposition of the diazonium salt alternately, it is possible to completely fix the two-color image of red and black. Also,
Since the color forming layer has a single layer structure, it is the easiest to form.

[0161]

As is apparent from the above description, according to the first photo-fixing type thermosensitive recording medium of the present invention, it contains a diazonium salt encapsulated in microcapsules, a coupler and a basic compound. In a light-fixing type thermosensitive recording medium having a coloring layer, a diazonium salt is added to 4-diazo-
4'-n-butyl diphenyl ether salt (4-diazo-4'-n
-butyl-diphenylether salt) and the coupler consisted of a first coupler composed of naphthol AS and a second coupler composed of naphthol AS-G.

When the light-fixing type heat-sensitive recording medium is constructed as described above, the red image can be completely fixed by sequentially performing the thermal writing and the decomposition of the diazonium salt.

Further, according to the second light-fixing type heat-sensitive recording medium of the present invention, the light-fixing type heat-sensitive recording comprising a coloring layer containing a diazonium salt encapsulated in microcapsules, a coupler and a basic compound. In the medium, the diazonium salt absorbs and decomposes a first diazonium salt that absorbs and decomposes a first light and a second light that does not decompose by the first light but has a shorter wavelength than the first light. A first diazonium salt, and a coupler which reacts with the first diazonium salt to develop a blue color and which reacts with the second diazonium salt to develop a magenta color; And a second coupler which reacts with a diazonium salt to develop a yellow color and which reacts with a second diazonium salt to develop a yellow color.

In the case of the light-fixing type heat-sensitive recording medium as described above, the two colors of red and black can be completely fixed by alternately performing the thermal writing and the decomposition of the diazonium salt.

In the second photo-fixing type thermosensitive recording medium of the present invention, the first diazonium salt is added to 4- (4'-
Methylphenylthio) -2,5-diethoxybenzenediazonium salt (4- (4'-Methylphenylthio) -2,5-Diethoxy
benzendiazonium salt), and the second diazonium salt is added to 4-diazo-4'-n-butyldiphenylether salt (4-diazo-4'-n-butyl-diphenylether Sal
t) and the first coupler is naphthol AS and the second coupler is naphthol AS-G, the microcapsules containing the second diazonium salt are Even if the ratio is reduced, a sufficient red color density can be obtained.

Further, according to the third light-fixing type heat-sensitive recording medium of the present invention, the light-fixing type heat-sensitive recording comprising a coloring layer containing a diazonium salt encapsulated in microcapsules, a coupler and a basic compound. In the medium, the diazonium salt absorbs and decomposes a first diazonium salt that absorbs and decomposes a first light and a second light that does not decompose by the first light but has a shorter wavelength than the first light. A first diazonium salt, a coupler that reacts with the first diazonium salt to develop a blue color, and a second diazonium salt that reacts with a magenta color to form a first coupler; A second coupler which reacts with a diazonium salt to develop a yellow color and which reacts with a second diazonium salt to develop a yellow color, and a second coupler which reacts with the first diazonium salt to develop a red color and a second diazonium salt. When It consisted of a third coupler which develops a color to yellow in response.

When the light-fixing type heat-sensitive recording medium is constructed as described above, by performing thermal writing and decomposition of the diazonium salt alternately, it is possible to completely fix the two-color image of red and black.

Further, according to the method for producing a light-fixing type thermosensitive recording medium of the present invention, only the diazonium salt that has been transferred to the aqueous phase until the microcapsule wall is formed is treated with a tetraphenylborate (TPB) group. The salt thus obtained is added to the water-existing solution to replace it with a thermally unstable tetraphenylborate (TPB) salt, which is then decomposed. By using the capsule, it is possible to reduce the color development caused by the reaction between the diazonium salt and the coupler when the coating liquid is prepared.

Also, tetraphenyl borate (TPB)
When the diazonium salt substituted with the salt is decomposed by heating, the decomposition treatment time can be shortened.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a light fixing type thermosensitive recording medium according to a first embodiment.

FIG. 2 is a reflection spectrum diagram of a photo-fixing type thermosensitive recording medium used in the description of the first embodiment.

FIG. 3 is a schematic cross-sectional view showing a light fixing type thermosensitive recording medium according to a second embodiment.

FIG. 4 is a schematic cross-sectional view showing a light fixing type thermal recording medium according to a third embodiment.

FIG. 5 is a color development characteristic diagram of a photo-fixing type thermosensitive recording medium used in the description of the third embodiment.

FIG. 6 is an absorbance spectrum diagram of a diazonium salt used in the description of the fourth embodiment.

FIG. 7 is an emission spectrum of a light source used in the first fixing step used in the description of the fourth embodiment.

FIG. 8 is a schematic sectional view showing an optical fixing type thermal recording medium according to a fifth embodiment.

FIG. 9 is a color development characteristic diagram of an optical fixing type thermosensitive recording medium, which is used for explaining a mode of a fifth embodiment.

[Explanation of symbols]

 10: Support 12: Coloring layer 14: Binder resin 16: Diazonium salt 16a: First diazonium salt 16b: Second diazonium salt 18: Coupler 18a: First coupler 18b: Second coupler 18c: Third Coupler 20: Basic compound 22: Sensitizer 100: Light fixing type heat sensitive recording medium of the first embodiment 200: Light fixing type heat sensitive recording medium of the second embodiment 300: Of the third embodiment Optical fixing type thermal recording medium 500: Optical fixing type thermal recording medium of the fifth embodiment

Claims (6)

[Claims] 1. A light-fixing type thermosensitive recording medium comprising a color-forming layer containing a diazonium salt encapsulated in microcapsules, a coupler and a basic compound, wherein the diazonium salt is replaced with 4-diazo-4′-n. -Butyl diphenyl ether salt (4-diazo-4'-n-butyl-diphenyle
ther salt), and the coupler comprises a first coupler composed of naphthol AS and a second coupler composed of naphthol AS-G. 2. A photo-fixing type thermosensitive recording medium comprising a color-forming layer containing a diazonium salt encapsulated in microcapsules, a coupler and a basic compound, wherein the diazonium salt absorbs first light. A coupler comprising a first diazonium salt which decomposes and a second diazonium salt which decomposes by absorbing second light which is not decomposed by the first light but has a shorter wavelength than the first light. A first coupler that reacts with the first diazonium salt to develop a blue color and reacts with the second diazonium salt to develop a magenta color, and a first coupler reacts with the first diazonium salt to develop a yellow color. And a second coupler which reacts with the second diazonium salt to develop a yellow color, and a light-fixing type heat-sensitive recording medium. 3. The light-fixing heat-sensitive recording medium according to claim 2, wherein the first diazonium salt is 4- (4′-methylphenylthio) -2,5-diethoxybenzenediazonium salt (4- (4'-Methylphenylthio) -2,5-Diethoxybenzendiaz
onium salt), and the second diazonium salt is added to 4-diazo-4′-n-
Butyl diphenyl ether salt (4-diazo-4'-n-butyl-dip
henylether salt), the first coupler comprises naphthol AS, and the second coupler comprises naphthol AS-G. 4. A photo-fixing type thermosensitive recording medium comprising a coloring layer containing a diazonium salt encapsulated in microcapsules, a coupler and a basic compound, wherein the diazonium salt absorbs a first light. A coupler comprising a first diazonium salt which decomposes and a second diazonium salt which decomposes by absorbing second light which is not decomposed by the first light but has a shorter wavelength than the first light. To a blue color by reacting with the first diazonium salt and a magenta color by reacting with the second diazonium salt, and a yellow color by reacting with the first diazonium salt. And a second coupler which reacts with the second diazonium salt to develop a yellow color,
A third color that develops red by reacting with the first diazonium salt and a yellow color by reacting with the second diazonium salt.
A photo-fixing type thermosensitive recording medium, characterized in that it comprises a coupler. 5. A photofixing type for producing a photofixing type thermosensitive recording medium by coating a mixed dispersion liquid containing a diazonium salt encapsulated in microcapsules, a coupler and a basic compound on a support and drying. In the method for producing a thermosensitive recording medium, when producing microcapsules encapsulating the diazonium salt, first, the microcapsule wall in a state of encapsulating the diazonium salt is formed by an interfacial polymerization method in a water-existing liquid, and then, , A salt having a tetraphenylborate group in the water-existing liquid is added, and only the diazonium salt dissolved in the water phase in the water-existing liquid is added to tetraphenylborate until the microcapsule wall is formed. A method for producing a light-fixing thermosensitive recording medium, which comprises substituting a salt and then decomposing the tetraphenylborate salt. 6. The method for producing a light-fixing type thermal recording medium according to claim 5, wherein the decomposition of the diazonium salt substituted with the tetraphenylborate salt is carried out by heating.
Thereafter, a microcapsule encapsulating the diazonium salt formed in the water-existing liquid, the coupler, and the basic compound are mixed to prepare a coating liquid, thereby producing a light-fixing heat-sensitive recording medium. Method.