JP3352900B2 - Light fixing type thermal recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fixing type thermosensitive recording medium.

[0002]

2. Description of the Related Art As one kind of thermal recording media, a microcapsule containing a diazonium salt, a basic compound,
A recording layer including a coupler and a recording layer provided on a support,
It is known (for example, Reference I: Tamotsu Kondo, “Microcapsules” P65-75, edited by the Japan Standards Association (199).
1)). The coloring mechanism in this thermosensitive recording medium is estimated as follows (page 72 of Document I). When heat is applied to the portion of the medium where recording is desired, the walls of the microcapsules swell and material permeability occurs on the walls. Therefore, the coupler, the diazonium salt and the basic compound come into contact with each other. The coupler and the diazonium salt have a property of reacting in an alkaline atmosphere, and since the basic compound generates an alkaline atmosphere, the coupler and the diazonium salt cause a reaction. As a result, an azo dye that contributes to color development is generated. A recording is made with this dye.

After the recording is completed, light of a predetermined wavelength is irradiated on the medium in order to fix the recording. The diazonium salt remaining in the medium is decomposed by this light and loses its activity. The medium is referred to as a light-fixing type thermosensitive recording medium because of its color forming mechanism and fixing mechanism. In addition, since the diazonium salt is isolated from the coupler by the microcapsules, this medium has an advantage that the risk of the diazonium salt reacting with the coupler during storage of the medium is small (the raw preservability is high).

[0004]

By the way, in the above-mentioned light fixing type thermosensitive recording medium, multicolor recording (recording is performed by
Hereinafter, it may be referred to as printing. ) Is also desired. This is because, for example, in gift certificates, commuter passes, various tickets, and the like, there are various useful applications as described below.

There is a case where a ticket made of a light-fixing type thermosensitive recording medium printed with a first color, for example, black or blue, is issued, and then the ticket is additionally written with a second color, for example, red. Specifically, an example is given in which a ticket printed in the first color is issued as a reservation ticket, and when the subsequent fee is paid, the ticket is printed with the fee paid in the second color. Alternatively, print a ticket, express ticket, etc. in the first color and issue it once,
An example in which, when performing a subsequent ticket inspection, an arbitrary print indicating that the ticket inspection has been completed is performed on the ticket or the like in a second color.

In a medium used for such an application, after printing in the first color, the printing can be fixed so that the printing is not falsified, and after the first printing is completed, the printing can be freely performed. It is necessary to be able to print in the second color.

As a conventional example of such a light fixing type heat-sensitive recording medium capable of multicolor printing, for example, Japanese Patent Application Laid-Open No. 3-28868.
There was one disclosed in Japanese Unexamined Patent Publication No. 8 (KOKAI). This light-fixing type thermosensitive recording medium had first to third recording layers on a support in this order. In addition, the first recording layer was a layer containing an electron-donating dye precursor and an electron-accepting compound as main components and, for example, a layer responsible for yellow coloring. Second
The recording layer was a layer containing a diazonium salt having a maximum absorption wavelength of 360 nm ± 20 nm and a coupler reacting with the diazonium salt, and a layer responsible for magenta coloring. The third recording layer was a layer containing a diazonium salt having a maximum absorption wavelength of 400 nm ± 20 nm and a coupler which reacts with the diazonium salt, and was a layer in charge of blue (for example, the upper right column to the lower left column on page 10 of the publication). Field).

In the optical fixing type thermal recording medium disclosed in Japanese Patent Application Laid-Open No. Hei 3-288688, multi-color printing can be performed by devising the energy for thermal printing and the wavelength of light for fixing the print after printing. (E.g., upper right column to lower left column on page 10 of the published gazette). Specifically, how much of the first to third layers the color is developed can be implemented by controlling the energy of thermal printing. When the medium is irradiated with light having a wavelength of about 400 nm after the completion of the first printing, the diazonium salt in the third layer is decomposed by the light and loses its activity. On the other hand, the diazonium salt in the second layer has a maximum absorption wavelength of 360 nm, and thus does not lose its activity with light near a wavelength of 400 nm. In the second printing, no color component is generated in the third layer, so that printing in a second color different from the first printing can be performed. Multicolor printing is performed using such a principle.

However, the method disclosed in Japanese Patent Application Laid-Open No. 3-28868
In the light-fixing type heat-sensitive recording medium disclosed in Japanese Patent Publication No. 8-3, it is necessary to provide three recording layers on a support, so that its production becomes difficult, and it is difficult to provide an inexpensive light-fixing type heat-sensitive recording medium.

[0010] Further, there is the following problem. When indoors or inside a car, which are typical use environments of the light-fixing type thermal recording medium, are considered, sunlight enters through the window glass into these indoors and the like. The current window glass cuts light with a wavelength of less than about 330 nm, but transmits light with a longer wavelength (for example, Reference II “Electro-Optical Handbook”, published by The Institute of Electrical Engineers of Japan, first edition of April 10, 1978, (See FIG. 2, spectral sensitivity on page 1522). Then, light having a wavelength of 330 nm or more always reaches the recording layer of the optical fixing type thermosensitive recording medium on which printing in the first color has been completed.

In such a case, Japanese Patent Application Laid-Open No. 3-288688
In the optical fixing type thermosensitive recording medium disclosed in Japanese Patent Application Laid-open No.
Since it is a diazonium salt having a maximum absorption wavelength at 0 nm, that is, a diazonium salt that loses its activity due to light having a wavelength of 330 nm or more, the second color after the printing with the first color is completed.
The diazonium salt is decomposed and loses its activity (hereinafter, also referred to as deactivation) by the light transmitted through the window glass until the color is printed.

The degree of this deactivation increases as the time from completion of printing in the first color to printing in the second color increases. Then, as the deactivation of the diazonium salt proceeds, the coloring ability of the second color decreases, so that the second printing with the second color cannot be performed as desired.

Accordingly, the present invention is a light-fixing type thermosensitive recording medium having a single recording layer and capable of multicolor printing, and has a long-term color developing ability of the second color even after recording of the first color is completed. There is a demand for a light-fixing type heat-sensitive recording medium which does not substantially impair the recording medium.

[0014]

According to the light fixing type heat-sensitive recording medium of the present invention, a dye which is contained in a microcapsule and which contributes to recording in a first color when reacted with a coupler is produced. A first diazonium salt which loses its activity when irradiated with the first light, and a dye which is encapsulated in the microcapsule and which reacts with the coupler to produce at least a second color which contributes to recording; A second diazonium salt that loses its activity when irradiated with a second light having a wavelength different from that of the second light, at least one kind of coupler as a coupler, and a basic compound that generates an atmosphere that causes the respective reactions. A recording layer containing the diazonium salt as a second diazonium salt represented by the following formula (1):
It is characterized by containing at least one selected from 4'-sec-butyldiphenylether hexafluorophosphate and 4-diazo-4'-tert-butyldiphenyletherhexafluorophosphate represented by the following formula (2).

[0015]

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Further, according to the photo-fixing type thermosensitive recording medium of the present invention, a dye which is contained in the microcapsule and which contributes to recording in the first color when reacted with the coupler is generated, and the first light is generated. A first diazonium salt that loses activity when irradiated and a dye that is encapsulated in a microcapsule and that reacts with a coupler to produce at least a second color-contributing recording, and that has a different wavelength from the first light A second diazonium salt that loses activity when irradiated with a second light;
A recording layer containing at least one kind of coupler as a coupler and a basic compound that generates an atmosphere for causing each of the reactions is provided on a support, and as a first diazonium salt,
It contains 4- (4′-methylphenylthio) -2,5-diethoxybenzenediazonium hexafluorophosphate represented by the following formula (4), and as a second diazonium salt, 4- (4) -methylphenylthio represented by the following formula (1) Diazo-4'-se
c-butyldiphenyl ether hexafluorophosphate, 4-diazo-4'-te represented by the following formula (2)
rt-butyl diphenyl ether hexafluorophosphate and 4-diazo- represented by the following formula (3)
It is characterized by containing at least one selected from 4'-n-butyldiphenylether hexafluorophosphate.

[0017]

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In the second diazonium salt, "at least" in the statement that a dye contributing to printing at least in the second color is formed means that the second diazonium salt is: The meaning is that any of the cases of contributing to both printing and printing with the second color and the case of contributing only to printing with the second color are acceptable. Of course, in most cases, the second diazonium salt forms a color even when printing with the first color. However, the present invention can also be applied when the second diazonium salt does not form a color when performing the first printing. It is the purpose.

According to the present invention, since the recording layer can be formed as a single layer, the production of the photo-fixing type thermosensitive recording medium is facilitated, and an inexpensive photo-fixing type thermosensitive recording medium can be provided.

Further, according to the photo-fixing type thermosensitive recording medium of the present invention, the above-mentioned (1) to (2) are used as the second diazonium salt.
Since it contains at least one selected from diazonium salts which lose their activity due to light having a wavelength shorter than 330 nm and is represented by the formula (3), the activity of the second diazonium salt is as follows: Light having a wavelength shorter than 330 nm is maintained in an environment that does not exist so as to affect the medium, for example, indoors or in a car. Further, if light having a wavelength of 330 nm or more is used as the first light for deactivating the first diazonium salt, the second diazonium is also used in the irradiation treatment with the first light for fixing the printing in the first color. The activity of the salt is maintained. Therefore, even after the printing and fixing of the first color have been completed, the coloring ability of the second color is not impaired for a long period (at least five years in the case of the following embodiment).

Each of the second diazonium salts represented by the above formulas (1) to (3) is a substance obtained by synthesis by the applicant of the present application (the synthesis method will be described later), and the details will be described later. However, it has the following features, for example.

First, since all of the second diazonium salts represented by the above formulas (1) to (3) have a maximum absorption wavelength near the wavelength of 310 nm, the room light is not affected even during the standing period after the first printing. Is not substantially deactivated.

Further, any of these second diazonium salts can react with a suitable coupler to form a red (magenta) azo dye. Therefore,
Red for printing in the first color (color that is relatively easy to call attention)
To be able to do with.

The second diazonium salt represented by the above formulas (1) to (3) can of course emit a dye in the first printing. Specifically, any of these second diazonium salts can react with a suitable coupler to form a red (magenta) azo dye even in the first printing, If a suitable coupler is used, it can react with it to produce a yellow (yellow) azo dye. Then, as the first diazonium salt, if a diazonium salt that generates at least a blue azo dye by reacting with the suitable coupler is used,
In the first printing, print in blue or 3
Printing in black by color addition becomes possible.

The second diazonium salts represented by the above formulas (1) to (3) all exhibit higher solubility in oil for preparing microcapsules than conventional red diazonium salts. . This means that the diazonium salt can be easily contained in the microcapsules, so that a heat-sensitive recording medium having a high coloring density can be realized. Therefore, these second diazonium salts are preferable as diazonium salts for thermosensitive recording media of the type using microcapsules.

In the above-mentioned photo-fixing type thermosensitive recording medium, the first diazonium salt is 4- (4'-methylphenylthio) -2,5-diethoxybenzenediazonium represented by the above formula (4). It is preferred to use hexafluorophosphate.

The first diazonium salt represented by the above formula (4) is used to (a) react with a suitable first coupler to form a blue (cyan) azo dye, and to react with a suitable second coupler. Reacts to produce a yellow (yellow) azo dye. Therefore, the first printing can be performed in blue or black (black generated by adding a red component from the second diazonium salt; details will be described later).

Further, since the first diazonium salt represented by the above formula (4) has a maximum absorption wavelength near the wavelength of 420 nm, the deactivation treatment of the first diazonium salt after the first printing is performed at a wavelength of around 420 nm. It can be performed using the light of Therefore, the second diazonium salt is not deactivated by the deactivation treatment of the first diazonium salt.

In implementing the present invention, the first
And at least one used with a second diazonium salt
As the kind of coupler, it is preferable to use two kinds of couplers of 2-hydroxy-3-naphthoic acid anilide represented by the following formula (5) and N- (2-benzothiazolyl) acetoacetamide represented by the following formula (6). It is.

[0030]

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The 2-hydroxy-3-naphthoic acid anilide reacts with the first diazonium salt represented by the above formula (4) to form a cyan azo dye, and the (1)
Reacts with at least one selected from the second diazonium salts represented by formulas (3) to (3) to produce a magenta azo dye. On the other hand, N- (2-benzothiazolyl) acetoacetamide reacts with the first diazonium salt represented by the above formula (4) to form a yellow azo dye,
It reacts with at least one selected from the second diazonium salts represented by the above formulas (1) to (3) to produce a yellow azo dye. Then, in the first printing,
Because cyan, magenta and yellow are mixed, the first
Black color can be printed.

In the second printing, since the first diazonium salt has been deactivated before that, magenta and yellow due to the second diazonium salt are mixed. Red color can be printed.

In implementing the present invention, the first
And at least one used with a second diazonium salt
As a kind of coupler, only 2-hydroxy-3-naphthoic acid anilide may be used.

The 2-hydroxy-3-naphthoic acid anilide reacts with the first diazonium salt represented by the above formula (4) to form a cyan azo dye, and the (1)
Reacts with at least one selected from the second diazonium salts represented by formulas (3) to (3) to produce a magenta azo dye. Then, in the first printing, cyan and magenta are mixed, so that blue printing can be performed as the first color. Further, in the second printing, since the first diazonium salt has been deactivated before that, only magenta due to the second diazonium salt is generated, and eventually, red printing as the second color is performed. I can do it.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the optical fixing type thermosensitive recording medium of the present invention will be described.

It is preferable that each of the first and second diazonium salts is contained in a microcapsule. This is because the reaction of the diazonium salt with the coupler (so-called pre-coupling) can be prevented before the original use of the light-fixing type thermosensitive recording medium, so that the raw preservability of the medium is improved.

Microcapsules containing a diazonium salt can be prepared in the form of a dispersion of microcapsules, for example, by the following known procedure described in Document I.

The first diazonium salt is dissolved in a liquid mixture of the microcapsule wall forming material and oil. A binder aqueous solution is mixed with this solution. By emulsifying this, a dispersion liquid of microcapsules containing the first diazonium salt can be prepared. The same treatment may be applied to the second diazonium salt.

If possible, the first and second diazonium salts may be encapsulated in the same microcapsule.

In preparing a dispersion of microcapsules containing a diazonium salt, a radical scavenger may be mixed. Here, the radical is a radical generated when a diazonium salt is decomposed and deactivated by light. These radicals have some color. These radicals often disappear in a short time, but some exist for a long time. Then, the color of the medium is impaired. The radical scavenger scavenges these radicals and prevents the color of the medium from being impaired.

On the other hand, the coupler is placed in a suitable aqueous binder solution to prepare a coupler dispersion. Further, a basic compound dispersion is prepared by adding a basic compound to a suitable aqueous binder solution. This can also be performed by a known method.

If necessary, a sensitizer is added to a suitable aqueous binder solution to prepare a sensitizer dispersion. The sensitizer causes a reaction between the diazonium salt and the coupler, for example, at lower energy. Of course, a sensitizer is not essential.

By mixing the above-mentioned respective dispersions, a coating solution for forming a light-fixing type thermosensitive recording medium can be obtained. This coating solution is applied to a support by any suitable method, and the coating film is dried to obtain a light-fixing type thermosensitive recording medium.

The shape and material of the support can be any suitable one according to the purpose of the light fixing type thermosensitive recording medium. The method of applying the coating solution to the support may be any suitable method.

Examples of the material for forming the microcapsule wall which can be used when preparing the dispersion liquid of the microcapsules include gelatin, polyurea, polyurethane, polyimide, polyester, polycarbonate and the like.

The oils that can be used include phosphoric acid esters, phthalic acid esters, other carboxylic acid esters,
Fatty acid amide, alkylated biphenyl, alkylated terphenyl, chlorinated paraffin, alkylated naphthalene,
Diarylethane and the like can be mentioned.

Specific examples include tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, tricyclohexyl phosphate, dibutyl phthalate, dioctyl phthalate, dilauryl phthalate, dicyclohexyl phthalate, butyl oleate, diethylene glycol dibenzoate, Dioctyl sebacate, dibutyl sebacate,
Dioctyl adipate, trioctyl trimellitate,
Acetyltriethyl citrate, octyl maleate, dibutyl maleate, isopropyldiphenyl, isoamylbiphenyl, chlorinated paraffin, diisopropylnaphthalene, 1,1'-ditolylethane, 2,4-ditert-aminophenol, N, N-dibutyl-2- Butoxy-5 tert-octylaniline and the like can be mentioned.

As a solubilizing agent for increasing the solubility of the diazonium salt in oil, any one selected from acetyl nitrile, cyclohexanone, ethyl acetate, butyl acetate, isopropyl acetate and methylene chloride may be mixed with the oil.

The binders used include polyvinyl alcohol, modified polyvinyl alcohol, methyl cellulose, sodium polystyrene sulfonate, ethylene /
Maleic acid copolymers and the like can be mentioned.

Examples of the basic compound (also referred to as an organic base) that can be used include organic ammonium salts, organic amines, amides, urea derivatives, thiourea derivatives, thiazoles, pyrroles, pyridines, piperazines, guanidines. , Indole, imidazole, imidazoline, trizole, morpholine, piperidine, amidine, pyridine and the like.

Specifically, tricyclohexylamine,
Tribenzylamine, octadecylbenzylamine, stearylamine, allylurea, thiourea, methylthiourea, allylthiourea, ethylenethiourea, 2-benzylimidazole, 4-phenylimidazole, 2-phenyl-4-methylimidazole, 2-undecylimidazoline 2,4,5-trifuryl-2-imidazoline,
1,2-diphenyl-4,4-dimethyl-2-imidazoline, 2-phenyl-2-imidazoline, 1,2,3-triphenylguanidine, 1,2-dicyclohexylguanidine, 1,2,3-tricyclohexylguanidine,
Guanidine trichloroacetate, N, N'-dibenzylpiperazine, 4,4'-dithiomorpholine, morpholinium trichloroacetate, 2-aminobenzothiazole, 2-benzoylhydrazinobenzothiazole and the like can be mentioned.

When a sensitizer is used, specific examples of the sensitizer include hydroxybenzoic acid derivatives, fatty acid amides, zinc stearate, α-naphthyl benzyl ether,
β-naphthylbenzyl ether, β-naphthoic acid phenyl ester, α-hydroxy-β-naphthoic acid phenyl ester, β-naphthol- (p-chlorobenzyl) ether, 1,4-butanediol phenyl ether,
1.4-butanediol-p-methylphenyl ether, 1,4-butanediol p-ethylphenyl ether, 1,4-butanediol-m-methylphenyl ether, 1-phenoxy-2- (p-ethylphenoxy)
Examples thereof include ethane, 1-phenoxy-2- (p-chlorophenoxy) ethane, and p-benzylbiphenyl.

Among these, specific examples of the hydroxybenzoic acid derivative include 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 2-hydroxybenzoic acid, isoamyl ester, 4-hydroxybenzoic acid n- Amyl ester, 4-hydroxybenzoic acid isoamyl ester, 2-hydroxybenzoic acid benzyl ester, 4-hydroxybenzoic acid benzyl ester, 2-
Hydroxybenzoic acid n-butyl ester, 2-hydroxybenzoic acid isobutyl ester, 4-hydroxybenzoic acid n-butyl ester, 4-hydroxybenzoic acid isobutyl ester, 4-hydroxybenzoic acid sec-butyl ester, 4-hydroxybenzoic acid n- Dodecyl ester, 2-hydroxybenzoic acid ethyl ester, 3-hydroxybenzoic acid ethyl ester, 4-hydroxybenzoic acid ethyl ester, 4′-hydroxybenzoic acid 2-ethylhexyl ester, 4-hydroxybenzoic acid n-heptyl ester, 4- Hydroxybenzoic acid n-hexyl ester, 4-hydroxybenzoic acid 2-hydrohexyl ester, 2-hydroxybenzoic acid isoamyl ester,
4-hydroxybenzoic acid isoamyl ester, 2-hydroxybenzoic acid isobutyl ester, 2-hydroxybenzoic acid isopropyl ester, 4-hydroxybenzoic acid isopropyl ester, 4-hydroxybenzoic acid lauryl ester, 4-hydroxybenzoic acid 4'-meso Diphenyl ester, methyl 2-hydroxybenzoate, methyl 3-hydroxybenzoate, n-nonyl 4-hydroxybenzoate, octyl 4-hydroxybenzoate, phenyl 2-hydroxybenzoate, 2-hydroxybenzoate Acid isopropyl ester, 4-hydroxybenzoic acid n-propyl ester, 4-hydroxybenzoic acid isopropyl ester, and the like.

Specific examples of the fatty acid amides include ethylene bisstearic acid amide, methylol stearic acid amide and the like.

The amounts of the first diazonium salt, the second diazonium salt, at least one kind of coupler and each of the basic compounds, and the amounts of the radical scavenger and the sensitizer which are added as required, are as follows. What is necessary is just to determine according to the specification of a light fixing type thermal recording medium.

[0056]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the light fixing type thermosensitive recording medium of the present invention will be described below. However, it should be understood that the materials used and the numerical conditions such as the amount, processing time, processing temperature, particle size and the like mentioned in the following description are only examples within the scope of the present invention.

1. First Example (a) Preparation of Microcapsule Dispersion Encapsulating the First Diazonium Salt As the first diazonium salt, 4- (4′-methylphenylthio) -2 represented by the above formula (4) was used. 5-Diethoxybenzenediazonium hexafluorophosphate (specifically, DH575PF6 (trade name) (manufactured by Daito Chemmix)) is used. Trimethylolpropane adduct of xylylene diisocyanate (specifically, Takenate D110N) as a wall forming material for microcapsules
(Manufactured by Takeda Pharmaceutical). Trimethylpropane triacrylate is used as a radical scavenger. Dibutyl phthalate is used as the oil. Ethyl acetate is used as a dissolution aid. Polyvinyl alcohol is used as a binder.

1 g of DH575PF6 and 12 g of D1
10N, 6 g of trimethylolpropane triacrylate and 3.8 g of ethyl acetate were dissolved in 6 g of dibutyl phthalate. To this solution, 81 g of an 8% by weight aqueous solution of polyvinyl alcohol was added as a binder aqueous solution. While stirring the solution, ultrasonic waves are applied to the solution,
This solution was emulsified by irradiating for 0.5 seconds at intervals of 0.5 seconds, including a rest time, for 20 seconds. 25 ml of water was added to this solution with further stirring, and this solution was irradiated with ultrasonic waves under the same conditions as above while further stirring. Further, 25 ml of water was added to the solution with stirring, and the solution was heated at 60 ° C. for 2 hours. Through this series of treatments, a microcapsule dispersion containing DH575PF6 and having an average particle size of 1.5 μm was obtained.

In order to deactivate DH575PF6 remaining in the dispersion without being taken in the microcapsules, 0.5 g of sodium tetraphenylborate is added to the dispersion, and Was stirred at room temperature for 1 hour. Hereinafter, this dispersion is referred to as “first microcapsule dispersion” for the sake of simplicity.

(B) Preparation of Microcapsule Dispersion Encapsulating Second Diazonium Salt As the second diazonium salt, 4-diazo-4′-n-butyldiphenylether hexafluorophosphate represented by the above formula (3) is used. Used. As the material for forming the wall of the microcapsule, the oil, and the binder, the materials described in the above section (a) are used.

(Description of Synthesis Method) First, 4-diazo-
4'-n-butyldiphenyl ether hexafluorophosphate was synthesized as follows.

Synthesis of 4-nitro-4′-n-butyldiphenyl ether First, 4-nitro-4′-n-butyldiphenylether was synthesized. Specifically, dimethylformamide 41
18.6 g of n-butylphenol, 25.0 g of p-bromonitrobenzene and 17.2 g of potassium carbonate were respectively added to the resulting mixture, and the mixture was stirred and reacted at 140 ° C. for 12 hours. After cooling the reaction solution to room temperature, the reaction solution is
The mixture was poured into 00 ml and extracted twice with 100 ml of ethyl acetate. After washing the extract (ie ethyl acetate solution) with water,
The extract was concentrated by evaporating the ethyl acetate as a solvent under reduced pressure. The extraction was concentrated until almost no ethyl acetate was evaporated. Thereafter, the concentrate was developed with n-hexane by silica gel column chromatography to obtain 30.2 g of 4-nitro-4′-n-butyldiphenyl ether.

: Synthesis of 4-amino-4'-n-butyldiphenylether Next, 4-amino-4'-n-butyldiphenylether was synthesized. Specifically, dimethylformamide 30
10 ml of concentrated hydrochloric acid (35 wt%: same in the following steps), 20 g of iron powder, and 45 ml of water were added to 0 ml, and the mixture was stirred at 95 ° C. for 1 hour, and further added with 4-nitro-
30.2 g of 4'-n-butyldiphenyl ether was added, and the mixture was stirred and reacted 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 evaporated. Thereafter, 200 ml of water at room temperature was poured into the concentrated solution, and 200 ml of ethyl acetate was added.
Extracted with ml. After the extract (that is, the ethyl acetate solution) was washed with water and dried, the extract was concentrated by evaporating ethyl acetate as a solvent under reduced pressure. The extraction was concentrated until almost no ethyl acetate was evaporated. Thereafter, the precipitated crystals were separated by filtration using filter paper, washed with a small amount of ethyl acetate, and dried, and 4-amino-4′-n-butyldiphenyl ether was converted to 25.4.
g was obtained.

Synthesis of 4-diazo-4′-n-butyldiphenylether hexafluorophosphate Next, 4-diazo-4′-n-butyldiphenyletherhexafluorophosphate was synthesized.

Specifically, 4-min.
Amino-4'-n-butyldiphenyl ether 25.4
g, and 69.1 g of concentrated hydrochloric acid was added dropwise. Then, 18.8 g of a 38 wt% aqueous solution of sodium nitrite was further added under ice-cooling.
Was dropped, the temperature was increased to 5 ° C., and the mixture was stirred for 30 minutes to cause a diazotization reaction. Thereafter, 29.3 g of potassium hexafluorophosphate was added to the reaction solution, and the mixture was stirred at 5 ° C. for 2 hours.
Then, the precipitated crystals are separated by filtration using filter paper, washed with water,
Drying was performed to obtain 28.2 g of 4-diazo-4′-n-butyldiphenylether hexafluorophosphate.

The above synthesizing method is a method described in Japanese Patent Application No. 8-17538 by the applicant of the present application.

Next, the above-mentioned synthesized diazonium salt was mixed with ¹ H
Identified by NMR. Varia as NMR device
Gemini 300 (model number) manufactured by n company was used. Also,
^As a sample for ¹ H NMR measurement, a solution prepared by dissolving 10 mg of a synthesized diazonium salt in 0.5 ml of heavy chloroform was used.

In the chart obtained by NMR measurement,
A doublet peak having a peak area ratio of 2 occurs around the position of the chemical shift value δ = 8.41 and the chemical shift value δ
= 7.26 as a center, a doublet peak with a peak area ratio of 2 occurs, and a chemical shift value δ = a doublet peak with a peak area ratio of 2 at a position of 7.16, and a chemical shift value δ = 7.00 as a center, a doublet peak with a peak area ratio of 2 occurs, and a chemical shift value δ = a triplet peak with a peak area ratio of 2 at a position of 2.64, and a chemical shift value δ =
A multiplet peak having a peak area ratio of 2 occurs at a position of 1.61 as a center, and a multiplet peak having a peak area ratio of 2 occurs at a position of a chemical shift value δ = 1.37. A triplet peak having a peak area ratio of 3 centered on the position at δ = 0.95. For a detailed discussion of the identification results, refer to Japanese Patent Application No.
No. 175038.

(Solubility in Oil) Next, the solubility of 4-diazo-4'-n-butyldiphenyl ether hexafluorophosphate in oil for forming microcapsules was examined. As a result, 8 g of this 4-diazo-4′-n-butyldiphenylether hexafluorophosphate was dissolved in 100 g of dibutyl phthalate and 12 g in 100 g of tricresyl phosphate.
g dissolved. With respect to 100 g of dibutyl phthalate or 100 g of tricresyl phosphate, the solubility of a conventional red-based diazonium salt, 4-diazodiphenyl ether hexafluorophosphate and 4-diazo-4′-methyldiphenyl ether hexafluorophosphate, Considering that the weight is 1.0 g or less, it can be understood that this 4-diazo-4'-n-butyldiphenylether hexafluorophosphate exhibits high solubility in dibutyl phthalate and tricresyl phosphate.

(Absorptivity spectrum)
-Diazo-4'-n-butyldiphenylether hexafluorophosphate was dissolved in dimethyl sulfoxide, and the absorption spectrum was examined. The result is shown in FIG.
Shown by solid lines inside. In FIG. 1, the wavelength is plotted on the horizontal axis,
The vertical axis indicates absorbance.

As can be seen from FIG. 1, 4-diazo-4 ′
-N-butyldiphenyletherhexafluorophosphate shows a maximum absorption peak at a wavelength of 310 nm. Also, it can be seen that there is no significant absorption peak at a wavelength of 330 nm or more. The sample whose absorption spectrum was measured was irradiated with light having a wavelength of 310 nm, and then the absorption spectrum was measured. As a result, it was found that the absorption peak at the wavelength of 310 nm had disappeared. This result is shown by a broken line in FIG. This indicates that 4-diazo-4'-n-butyldiphenyletherhexafluorophosphate is decomposed when irradiated with light having a central wavelength of 310 nm or a wavelength near 310 nm.

(Preparation of Dispersion) Next, 1 g of 4-diazo-4'-n-butyldiphenyletherhexafluorophosphate and 12 g of D110N were dissolved in 12 g of dibutyl phthalate. An 8% by weight aqueous solution of polyvinyl alcohol was added to this solution as an aqueous binder solution.
1 g was added. While stirring the solution, ultrasonic waves were applied to the solution for 0.5 seconds at intervals of 0.5 seconds, including a pause.
This solution was emulsified by irradiation for 0 seconds. 25 ml of water was added to the solution with further stirring, and the solution was irradiated with ultrasonic waves under the same conditions as above while further stirring. Further, the solution was stirred for 25 m.
l of water was added and the solution was heated at 4 ° C for 6 hours. Through this series of treatments, a microcapsule dispersion containing the second diazonium salt and having an average particle size of 1.5 μm was obtained.

The 4-diazo-4'-n- remaining in the above-mentioned dispersion without being taken in the microcapsules.
In order to inactivate butyl diphenyl ether hexafluorophosphate, 0.5 g of sodium tetraphenylborate was added to the dispersion, and the dispersion was stirred at room temperature for 3 hours. Hereinafter, this dispersion is referred to as “second microcapsule dispersion” for convenience of explanation.

(C) Preparation of First Coupler Dispersion As the first coupler, a 2-coupler represented by the above formula (5) is used.
10 g of hydroxy-3-naphthoic acid anilide (specifically, Azoic Coupling Component 2 (trade name, manufactured by Tokyo Chemical Industry Co., Ltd.)) was added to 50 g of a 5% by weight aqueous solution of polyvinyl alcohol, and mixed and dispersed by a ball mill for 3 days. A coupler dispersion was prepared, and the average particle size of the dispersed particles in the first coupler dispersion was about 2 μm.

(D) Preparation of Second Coupler Dispersion As the second coupler, the N-type coupler represented by the above formula (6) is used.
10 g of (2-benzothiazolyl) acetoacetamide (specifically, trade name Naphthol-ASL4G (manufactured by Hoechst))
Was added to 50 g of a 5% by weight aqueous solution of polyvinyl alcohol, and mixed and dispersed by a ball mill for 3 days to prepare a second coupler dispersion. The average particle size of the dispersed particles in the second coupler dispersion was about 2 μm.

(E) Preparation of Basic Compound Dispersion 10 g of triphenylguanidine was added as a basic compound.
The mixture was added to 50 g of a 5% by weight aqueous solution of polyvinyl alcohol, and mixed and dispersed by a ball mill for 3 days to prepare a basic compound dispersion. The average particle size of the dispersed particles in this basic compound dispersion was about 2 μm.

(F) Preparation of Sensitizer Dispersion A dispersion of ethylene bisstearic acid amide as a sensitizer, here, a commercially available product in which ethylene bisstearic acid amide is already dispersed (trade name B961 (manufactured by Chukyo Yushi) )) Was prepared. This B961 is a dispersion containing 28.0% by weight of ethylene bisstearic acid amide.

(G) Preparation of light fixing type thermosensitive recording medium 80 parts by weight of the first microcapsule dispersion, 20 parts by weight of the second microcapsule dispersion, 8 parts by weight of the first coupler dispersion, 2 parts by weight of the coupler dispersion liquid, 20 parts by weight of the basic compound dispersion liquid, and 30 parts by weight of the sensitizer dispersion liquid were mixed to obtain a coating liquid for forming a photo-fixing type thermosensitive recording medium of the first example. .

Next, this coating solution was applied by a bar coater onto a white paper as a support in this case. The coated paper was dried with a hot air dryer at 40 ° C.

Thus, microcapsules containing the first diazonium salt and the radical scavenger, microcapsules containing the second diazonium salt, the first coupler, the second coupler, the basic compound, and the sensitizer Thus, the photo-fixable thermosensitive recording medium of the first embodiment having a recording layer containing on a support is obtained.

The drying time of the coating film was set to 20 minutes. The coating amount of the coating solution was 12 g / m ^{2 as} a dry coating amount.

(H) Confirmation of Coloring Characteristics First printing (first printing) is performed on the optical fixing type thermosensitive recording medium of the first embodiment manufactured as described above by a thermal printer. The optical density of the printed portion was measured by a Macbeth (Macbeth) optical densitometer. As a result, it was found that a clear black color development with a black base optical density of 1.15 occurred in this printed portion.

The principle of the occurrence of black color at the time of the first printing is as follows. At the time of this printing, a cyan azo dye is produced by a reaction between the first diazonium salt and the first coupler, and a yellow azo dye is produced by a reaction between the first diazonium salt and the second coupler, Reacting the second diazonium salt with the first coupler to form a magenta azo dye,
In addition, a yellow azo dye is produced by the reaction between the second diazonium salt and the second coupler. Since these azo dyes of cyan, yellow and magenta are mixed, a black color is generated.

Next, in order to deactivate the first diazonium salt remaining in the recording layer in an unreacted state, the light-fixed thermosensitive recording medium of the first embodiment after the first printing was completed. On the other hand, an ultraviolet ray having a wavelength of 420 nm was irradiated.

Next, a second printing (second printing) is performed by a thermal head on a portion of the light fixing type thermosensitive recording medium of the first embodiment which has not been printed yet, and this printing is performed. The optical density of the part was measured with a Macbeth optical densitometer. As a result, it was found that a clear red color development having a black base optical density of 0.35 and a magenta base optical density of 0.55 occurred in the printed portion. In the second printing, a magenta azo dye generated due to a reaction between the second diazonium salt and the first coupler and a reaction generated between the second diazonium salt and the second coupler are generated. Although yellow azo dyes are produced, they are visually recognized as red.
The optical density of the red color obtained here is hereinafter referred to as an initial color density for convenience of explanation.

Next, as described above, the first printing and the second printing are performed.
When the sample after printing is left in its normal use environment (typically, indoors), how the red color developing ability changes with this standing time will be described below. It was investigated by an accelerated test.

First, the sample was forcibly irradiated with the light of the 40 W white fluorescent lamp (here, FLR40S manufactured by Toshiba Lighting & Technology Co., Ltd.) was separated from the sample by 1 cm. The fluorescent lamp used here has a wavelength of 440.
It has a remarkable first peak near nm. Further, assuming that the intensity of the first peak is 100%, the wavelength 559n
m, peak of specific energy about 75%, wavelength 580n
m, a peak at a specific energy of about 70%, a wavelength of 400 n
m, a peak at a specific energy of about 50%, and a wavelength of 320 n
m, a fluorescent lamp having a specific energy peak of about 5% (Technical Data Sheet (Toshiba Lighting & Technology Corp., 1994)
−04). ).

The forced irradiation time of the fluorescent light was set to 1 minute, 1 minute,
Samples were prepared for 2 minutes and 1 hour, respectively. Here, the irradiation time of 1 minute, 12 minutes, and 1 hour correspond to one month, one year, and five years, respectively, when converted into a normal environmental leaving time.

The unprinted portion of each sample which had been subjected to the forced irradiation of the fluorescent lamp under the above conditions was printed by a thermal head, and the optical density of the printed portion was determined by the Macbeth optical density. Each was measured with a meter.

In a sample printed after forcibly irradiating the light of a fluorescent lamp for 1 minute, a clear red color with a black base optical density of 0.35 and a magenta base optical density of 0.55 is generated in the printed portion. I understood.

In the sample printed after forcibly irradiating the light of a fluorescent lamp for 12 minutes, a clear red color with a black base optical density of 0.34 and a magenta base optical density of 0.55 is generated in the printed portion. I understood.

In a sample printed after forcibly irradiating the light of a fluorescent lamp for one hour, a clear red color with a black base optical density of 0.31 and a magenta base optical density of 0.55 is generated in the printed portion. I understood.

The results of the color densities are shown in Table 1 together with the above initial color densities.

[0094]

[Table 1]

As can be seen from the above description, according to the optical fixing type thermosensitive recording medium of the first embodiment, the black
Can be printed, and black printing can be performed using light (wavelength 420 nm).
It can be seen that the second printing with red is possible even after the medium has been left in its normal use environment for a long period of time (at least 5 years in terms of experimental results) after black printing has been completed.

The sample subjected to the above-mentioned forced irradiation, followed by printing and optical density measurement was subjected to a wavelength of 310 nm.
UV light was applied. Then, printing was performed by a thermal head on each of the unprinted portions of these samples. However, no color was observed in any of the samples. The reason why no color formation was observed is that the second diazonium salt absorbs light having a wavelength of 310 nm and is inactivated.

2. Second Example As described above, 80 parts by weight of the first microcapsule dispersion, 20 parts by weight of the second microcapsule dispersion, 10 parts by weight of the first coupler dispersion, 20 parts by weight of the basic compound dispersion, and 30 parts by weight of the sensitizer dispersion were mixed to obtain a coating liquid for forming a photo-fixable thermosensitive recording medium of the second embodiment. That is,
A coating solution was prepared, which is a major difference from the first embodiment in that the second coupler was not used.

Next, this coating solution was applied by a bar coater onto a white paper as a support in this case. The coated paper was dried with a hot air dryer at 40 ° C.

Thus, a microcapsule containing the first diazonium salt and the radical scavenger, a microcapsule containing the second diazonium salt, the first coupler, the recording layer containing the basic compound and the sensitizer were prepared. Thus, the light fixing type thermosensitive recording medium of the second embodiment provided on the support can be obtained.

The drying time of the coating film was set to 20 minutes. The coating amount of the coating solution was 10 g / m ^{2 as} a dry coating amount.

The first printing (first printing) is performed by the thermal printer on the optical fixing type thermal recording medium of the second embodiment manufactured as described above, and the optical density of the printed portion is determined. Measured with a Macbeth optical densitometer. As a result, it was found that a clear blue color development having a cyan base optical density of 1.25 occurred in this printed portion. In the first printing, a reaction between the first diazonium salt and the first coupler generates a cyan azo dye, and a reaction between the second diazonium salt and the first coupler generates a magenta azo dye. Are visually recognized as cyan (blue) due to the amount of the diazonium salt.

Next, in order to deactivate the first diazonium salt remaining in the recording layer in an unreacted state, the photo-fixable thermosensitive recording medium of the second embodiment after the first printing was completed. On the other hand, an ultraviolet ray having a wavelength of 420 nm was irradiated.

Next, a second printing (second printing) is performed by a thermal head on a portion of the light fixing type thermal recording medium according to the second embodiment which has not been printed yet, and The optical density of the part was measured with a Macbeth optical densitometer. As a result, it was found that a clear red color development having a black base optical density of 0.42 and a magenta base optical density of 0.62 occurred in the printed portion. This coloring is the second
Is caused by the reaction between the diazonium salt and the first coupler. The optical density of the red color obtained here is hereinafter referred to as an initial color density for convenience of explanation.

Next, an acceleration test using a white fluorescent lamp was performed on the light fixing type thermal recording medium of the second embodiment in the same procedure as in the first embodiment. The results are shown in Table 2 below.

[0105]

[Table 2]

As can be seen from the above description, according to the light-fixing type thermosensitive recording medium of the second embodiment, the first
Can be printed, and blue printing can be performed using light (wavelength 420 nm).
It can be understood that the second printing by red is possible even after the medium has been left in its normal use environment for a long period of time (at least 5 years in terms of experimental results) after completion of the blue printing.

The sample subjected to the above-mentioned forced irradiation, followed by printing and optical density measurement was set to a wavelength of 310 nm.
UV light was applied. Then, printing was performed by a thermal head on each of the unprinted portions of these samples. However, no color was observed in any of the samples. The reason why no color formation was observed is that the second diazonium salt absorbs light having a wavelength of 310 nm and is inactivated.

3. Third Example As the second diazonium salt, 4-diazo-4′-sec-butyldiphenylether hexafluorophosphate represented by the above formula (1) is used. The embodiment will be described.

(Description of Synthesis Method) First, this 4-diazo-4'-sec-butyldiphenyletherhexafluorophosphate was synthesized as follows.

Synthesis of 4-nitro-4'-sec-butyldiphenyl ether To 20 ml of dimethylformamide, 10.1 g of p-butylphenol, 10.0 g of p-chloronitrobenzene and 10.5 g of potassium carbonate were added, respectively. The mixture was stirred for an hour to react. After cooling the reaction solution to room temperature,
This reaction solution was poured into 150 ml of water at normal temperature, and extracted with 150 ml of ethyl acetate. The extract (that is, the ethyl acetate solution) is diluted with 100 ml of a 5% aqueous sodium hydroxide solution.
After washing once with 10% saline, the extract was concentrated by evaporating ethyl acetate as a solvent under reduced pressure. Concentration of the extract was continued until almost no ethyl acetate was evaporated, yielding 17.6 g of 4-nitro-4'-sec-butyldiphenyl ether.

Next, 6.35 g of concentrated hydrochloric acid (35 wt%: same in the following steps), 21.7 g of iron powder and 72 ml of water were added to 90 ml of toluene. After stirring at 85 ° C. for 1 hour,
A solution in which 5.0 g of 4-nitro-4'-sec-butyldiphenyl ether was dissolved in 27 ml of toluene was added, and the mixture was stirred and reacted at 85 ° C for 1 hour. After cooling the reaction solution to room temperature, the reaction solution was neutralized with a 20% aqueous sodium carbonate solution, filtered, the organic layer was washed with water, and the filtrate was concentrated by evaporating toluene as a solvent under reduced pressure. The filtrate was concentrated until almost no toluene evaporated. Thereafter, the precipitated crystals were separated by filtration using filter paper and dried, and 13.0 g of 4-amino-4′-se was obtained.
c-Butyl diphenyl ether was obtained.

Synthesis of 4-diazo-4'-sec-butyldiphenylether hexafluorophosphate To 204 ml of water, 10.0 g of 4-amino-4'-sec-butyldiphenylether and 25.9 g of concentrated hydrochloric acid were added, and the mixture was cooled on ice. 20 wt% sodium nitrite aqueous solution
The mixture was added dropwise, and stirred for 1.5 hours to cause a diazotization reaction. Thereafter, 8.43 g of potassium hexafluorophosphate was added to the reaction solution, and the mixture was stirred at 2 ° C. for 30 minutes. And
The precipitated crystals were separated by filtration using filter paper, washed with water, and dried to obtain 10.0 g of 4-diazo-4′-sec-butyldiphenyletherhexafluorophosphate.

The above synthesized 4-diazo-4'-sec-
Butyl diphenyl ether hexafluorophosphate was identified by ¹ H-NMR in the same manner as in the first example.

In the chart obtained by the NMR measurement,
A doublet peak having a peak area ratio of 2 occurs around the position of the chemical shift value δ = 8.43, and the chemical shift value δ
= 7.29 as a center, a doublet peak having a peak area ratio of 2 occurs, and a chemical shift value δ = a doublet peak having a peak area ratio of 2 occurs at a position of 7.18, and a chemical shift value δ = 7.03 as a center, a doublet peak with a peak area ratio of 2 occurs, and a chemical shift value δ = a multiplet peak with a peak area ratio of 1 at a position of 2.65 as a center, and a chemical shift value δ =
A multiplet peak having a peak area ratio of 2 is generated around the position of 1.61, a doublet peak having a peak area ratio of 3 is generated around the position of the chemical shift value δ = 1.27, and a chemical shift value δ is generated. A triplet peak having a peak area ratio of 3 centered on the position of = 0.86.

(Solubility in Oil) Next, the solubility of 4-diazo-4'-sec-butyldiphenyl ether hexafluorophosphate in oil for forming microcapsules was examined. As a result, it was confirmed that 10 g or more of 4-diazo-4′-sec-butyldiphenylether hexafluorophosphate was dissolved in 100 g of dibutyl phthalate and 100 g of tricresyl phosphate.

(Absorption spectrum) Next, 4-diazo-
When the absorption spectrum of 4'-sec-butyldiphenyletherhexafluorophosphate was measured by the same procedure as in the first example, 4-diazo-4'-n
The absorption spectrum was similar to that of -butyldiphenyl ether hexafluorophosphate.

(Preparation of Dispersion) Next, 4-diazo-4 ′
A dispersion of microcapsules containing -sec-butyldiphenyletherhexafluorophosphate was prepared according to the procedure described in the section (b) of the first embodiment.

(Preparation of Light-Fixed Thermosensitive Recording Medium) Next, the microcapsule dispersion containing 4-diazo-4'-sec-butyldiphenyletherhexafluorophosphate is used as a second microcapsule dispersion. Except for the above, a light-fixed thermosensitive recording medium (the light-fixed thermosensitive recording medium of the third embodiment) was manufactured under the conditions described in the section (g) of the first embodiment.

(Coloring Characteristics) The first printing (first printing) is performed by the thermal printer on the photo-fixable thermosensitive recording medium of the third embodiment manufactured as described above, and the printed portion is printed. Was measured with a Macbeth optical densitometer. As a result, it was found that a clear black color development having a black base optical density of 1.15 occurred in this printed portion. This principle of coloring is the same as in the first embodiment.

Next, in order to deactivate the first diazonium salt remaining in the recording layer in an unreacted state, the light-fixing type thermosensitive recording medium of the third embodiment after the first printing was completed. On the other hand, an ultraviolet ray having a wavelength of 420 nm was irradiated.

Next, a second printing (second printing) is performed by a thermal head on a portion of the light fixing type thermosensitive recording medium of the third embodiment which has not been printed yet, and this printing is performed. The optical density of the part was measured with a Macbeth optical densitometer. As a result, it was found that a clear red color development having a black base optical density of 0.34 and a magenta base optical density of 0.54 occurred in the printed portion. This coloring principle is
This is the same as in the first embodiment. The optical density of the red color obtained here is hereinafter referred to as an initial color density for convenience of explanation.

Next, the light-fixing type thermosensitive recording medium of the third embodiment was subjected to an acceleration test using a white fluorescent lamp in the same procedure as in the first embodiment. The results are shown in Table 3 below.

[0123]

[Table 3]

As can be seen from the above description, according to the photo-fixable thermosensitive recording medium of the third embodiment, the first black
Can be printed, and black printing can be performed using light (wavelength 420 nm).
It can be seen that the second printing with red is possible even after the medium has been left in its normal use environment for a long period of time (at least 5 years in terms of experimental results) after black printing has been completed.

The sample having the wavelength of 310 nm was subjected to the above-described forced irradiation, and subsequent printing and optical density measurement.
UV light was applied. Then, printing was performed by a thermal head on each of the unprinted portions of these samples. However, no color was observed in any of the samples. The reason why no color formation was observed is that the second diazonium salt absorbs light having a wavelength of 310 nm and is inactivated.

4. Fourth Example Next, a description will be given in a second example except that a microcapsule dispersion liquid containing 4-diazo-4′-sec-butyldiphenyletherhexafluorophosphate is used as a second microcapsule dispersion liquid. Under these conditions, an optical fixing type thermal recording medium (the optical fixing type thermal recording medium of the fourth embodiment) was produced. That is, a light-fixing type thermosensitive recording medium was manufactured, which is a major difference from the third embodiment in that the second coupler was not used.

The first printing (first printing) is performed on the thus-prepared optical fixing type thermal recording medium of the fourth embodiment by a thermal printer, and the optical density of the printed portion is determined by Macbeth. (Macbeth) Measured with an optical densitometer. As a result, it was found that a clear blue color development having a cyan base optical density of 1.25 occurred in this printed portion. This coloring principle is the same as in the second embodiment.

Next, in order to deactivate the first diazonium salt remaining in an unreacted state in the recording layer, the light-fixing type thermosensitive recording medium of the fourth embodiment after the first printing was completed. On the other hand, an ultraviolet ray having a wavelength of 420 nm was irradiated.

Next, a second printing (second printing) is performed by a thermal head on the unfixed portion of the light fixing type thermal recording medium of the fourth embodiment, and this printing is performed. The optical density of the part was measured with a Macbeth optical densitometer. As a result, it was found that a clear red color development having a black base optical density of 0.41 and a magenta base optical density of 0.61 occurred in the printed portion. This coloring principle is
This is the same as the case of the second embodiment. The optical density of the red color obtained here is hereinafter referred to as an initial color density for convenience of explanation.

Next, an acceleration test using a white fluorescent lamp was performed on the light-fixing type thermosensitive recording medium of the fourth embodiment in the same procedure as in the first embodiment. The results are shown in Table 4 below.

[0131]

[Table 4]

As can be seen from the above description, according to the photo-fixed thermosensitive recording medium of the fourth embodiment, the first
Can be printed, and blue printing can be performed using light (wavelength 420 nm).
It can be understood that the second printing by red is possible even after the medium has been left in its normal use environment for a long period of time (at least 5 years in terms of experimental results) after completion of the blue printing.

Each sample after the above-mentioned forced irradiation and subsequent printing and optical density measurement was performed at a wavelength of 310 nm.
UV light was applied. Then, printing was performed by a thermal head on each of the unprinted portions of these samples. However, no color was observed in any of the samples. The reason why no color formation was observed is that the second diazonium salt absorbs light having a wavelength of 310 nm and is inactivated.

5. Fifth Example As the second diazonium salt, 4-diazo-4′-tert-butyldiphenylether hexafluorophosphate represented by the above formula (2) is used. The embodiment will be described.

(Description of Synthesis Method) First, this 4-diazo-4'-tert-butyldiphenyl ether hexafluorophosphate was synthesized as follows.

Synthesis of 4-nitro-4'-t-butyldiphenyl ether To 20 ml of dimethylformamide, 18.6 g of p-butylphenol, 10.0 g of p-chloronitrobenzene and 10.5 g of potassium carbonate were added, respectively. The mixture was stirred for an hour to react. After cooling the reaction solution to room temperature,
This reaction solution was poured into 150 ml of water at normal temperature, and extracted with 150 ml of ethyl acetate. The extract (that is, the ethyl acetate solution) is diluted with 100 ml of a 5% aqueous sodium hydroxide solution.
After washing once with 10% saline, the extract was concentrated by evaporating ethyl acetate as a solvent under reduced pressure. Concentration of the extract was continued until almost no ethyl acetate evaporated, yielding 17.6 g of 4-nitro-4'-t-butyldiphenyl ether.

Next, 6.35 g of concentrated hydrochloric acid (35 wt%: same in the following steps), 21.7 g of iron powder and 72 ml of water were added to 90 ml of toluene. After stirring at 85 ° C. for 1 hour,
A solution in which 5.0 g of 4-nitro-4'-t-butyldiphenyl ether was dissolved in 27 ml of toluene was added, and the mixture was stirred and reacted at 85 ° C for 1 hour. After cooling the reaction solution to room temperature, the reaction solution was neutralized with a 20% aqueous sodium carbonate solution, filtered, the organic layer was washed with water, and the filtrate was concentrated by evaporating toluene as a solvent under reduced pressure. The filtrate was concentrated until almost no toluene evaporated. Thereafter, the precipitated crystals were separated by filtration using filter paper and dried to obtain 12.5 g of 4-amino-4′-t-butyldiphenyl ether.

Synthesis of 4-diazo-4′-t-butyldiphenylether hexafluorophosphate Next, to 204 ml of water, 10.0 g of 4-amino-4′-t-butyldiphenylether and 25.9 g of concentrated hydrochloric acid were added. 20% by weight aqueous sodium nitrite solution 17 under ice-cooling
ml was added dropwise and stirred for 1 hour to cause a diazotization reaction. Thereafter, potassium hexafluorophosphate (8.43) was added to the reaction solution.
g was added and stirred at 2 ° C. for 30 minutes. 7. The precipitated crystals are separated by filtration using filter paper, washed with water, and dried.
8 g of 4-diazo-4'-t-butyldiphenylether hexafluorophosphate were obtained. Next, the 4-diazo-4′-tert-butyldiphenylether hexafluorophosphate synthesized in this manner was converted into ¹ H—N
It was identified by MR in the same manner as in the first embodiment.

In the chart obtained by NMR measurement,
A doublet peak having a peak area ratio of 2 occurs around the position of the chemical shift value δ = 8.44, and the chemical shift value δ
= 7.50 as a center, a doublet peak with a peak area ratio of 2 is generated, and a chemical shift value δ is a doublet with a peak area ratio of 2 at a position of 7.19, and a chemical shift value δ = 7.03 as a center, a doublet peak with a peak area ratio of 2 was generated, and a singlet peak with a peak area ratio of 9 was generated at a chemical shift value δ = 1.36 center.

(Solubility in Oil) Next, the solubility of 4-diazo-4'-t-butyldiphenyl ether hexafluorophosphate in oil for forming microcapsules was examined. As a result, 4-diazo-
It was found that 8 g or more of 4'-t-butyldiphenylether hexafluorophosphate was dissolved in 100 g of dibutyl phthalate and 100 g of tricresyl phosphate.

(Absorption spectrum) Next, 4-diazo-
When the absorption spectrum of 4'-tert-butyldiphenyletherhexafluorophosphate was measured by the same procedure as in the first example, 4-diazo-4'-
The absorption spectrum was similar to that of n-butyldiphenyl ether hexafluorophosphate.

(Preparation of Dispersion) Next, 4-diazo-4 ′
-Microcapsule dispersion containing tert-butyl diphenyl ether hexafluorophosphate,
The adjustment was performed according to the procedure described in the section (b) of the first embodiment.

(Preparation of Medium) Next, 4-diazo-4'-
The microcapsule dispersion containing tert-butyl diphenyl ether hexafluorophosphate was added to the second
A light-fixing type heat-sensitive recording medium (a light-fixing type heat-sensitive recording medium of the fifth example) was produced under the conditions described in section (g) of the first example, except that the liquid dispersion was prepared as a dispersion liquid of a black capsule. .

(Coloring Characteristics) The first printing (first printing) is performed by the thermal printer on the light-fixed thermosensitive recording medium of the fifth embodiment manufactured as described above, and the printed portion is printed. Was measured with a Macbeth optical densitometer. As a result, it was found that a clear black color development having a black base optical density of 1.15 occurred in this printed portion. This principle of coloring is the same as in the first embodiment.

Next, in order to deactivate the first diazonium salt remaining in the recording layer in an unreacted state, the light-fixed thermosensitive recording medium of the fifth embodiment after the first printing was completed. On the other hand, an ultraviolet ray having a wavelength of 420 nm was irradiated.

Next, a second printing (second printing) is performed by a thermal head on the unprinted portion of the light-fixing type thermal recording medium of the fifth embodiment, and this printing is performed. The optical density of the part was measured with a Macbeth optical densitometer. As a result, it was found that a clear red color development having a black base optical density of 0.36 and a magenta base optical density of 0.56 occurred in the printed portion. This coloring principle is
This is the same as in the first embodiment. The optical density of the red color obtained here is hereinafter referred to as an initial color density for convenience of explanation.

Next, the light-fixing type thermosensitive recording medium of the fifth embodiment was subjected to an acceleration test using a white fluorescent lamp in the same procedure as in the first embodiment. The results are shown in Table 5 below.

[0148]

[Table 5]

As can be seen from the above description, according to the photo-fixable thermosensitive recording medium of the fifth embodiment, the first black
Can be printed, and black printing can be performed using light (wavelength 420 nm).
It can be seen that the second printing with red is possible even after the medium has been left in its normal use environment for a long period of time (at least 5 years in terms of experimental results) after black printing has been completed.

The sample subjected to the above-mentioned forced irradiation, followed by printing and optical density measurement was subjected to a wavelength of 310 nm.
UV light was applied. Then, printing was performed by a thermal head on each of the unprinted portions of these samples. However, no color was observed in any of the samples. The reason why no color formation was observed is that the second diazonium salt absorbs light having a wavelength of 310 nm and is inactivated.

6. Sixth Example Next, a microcapsule dispersion containing 4-diazo-4′-tert-butyldiphenyletherhexafluorophosphate was used as a second microcapsule dispersion, except that the dispersion was a second microcapsule dispersion. Under the conditions described, an optical fixing type thermal recording medium (optical fixing type thermal recording medium of the sixth embodiment) was produced. That is, an optical fixing type heat-sensitive recording medium was produced, which is a great difference from the fifth embodiment in that the second coupler was not used.

The first printing (first printing) is performed on the thus-prepared optical fixing type thermal recording medium of the sixth embodiment by a thermal printer, and the optical density of the printed portion is determined by Macbeth. (Macbeth) Measured with an optical densitometer. As a result, it was found that a clear blue color development having a cyan base optical density of 1.25 occurred in this printed portion. This coloring principle is the same as in the second embodiment.

Next, in order to deactivate the first diazonium salt remaining in the recording layer in an unreacted state, the light-fixed heat-sensitive recording medium of the sixth embodiment after the first printing was completed. On the other hand, an ultraviolet ray having a wavelength of 420 nm was irradiated.

Next, a second printing (second printing) is performed by a thermal head on a portion of the light fixing type thermal recording medium according to the sixth embodiment, on which printing has not yet been performed. The optical density of the part was measured with a Macbeth optical densitometer. As a result, it was found that a clear red color development having a black base optical density of 0.43 and a magenta base optical density of 0.63 occurred in the printed portion. This coloring principle is
This is the same as the case of the second embodiment. The optical density of the red color obtained here is hereinafter referred to as an initial color density for convenience of explanation.

Next, the light-fixing type thermosensitive recording medium of the sixth embodiment was subjected to an acceleration test using a white fluorescent lamp in the same procedure as in the first embodiment. The results are shown in Table 6 below.

[0156]

[Table 6]

As can be seen from the above description, according to the photo-fixing type thermal recording medium of the sixth embodiment, the first blue
Can be printed, and blue printing can be performed using light (wavelength 420 nm).
It can be understood that the second printing by red is possible even after the medium has been left in its normal use environment for a long period of time (at least 5 years in terms of experimental results) after completion of the blue printing.

[0158] Each of the samples subjected to the above-described forced irradiation, and subsequent printing and optical density measurement was performed at a wavelength of 310 nm.
UV light was applied. Then, printing was performed by a thermal head on each of the unprinted portions of these samples. However, no color was observed in any of the samples. The reason why no color formation was observed is that the second diazonium salt absorbs light having a wavelength of 310 nm and is inactivated.

[0159]

As is evident from the above description, according to the photo-fixing type thermosensitive recording medium of the present invention, when it reacts with the coupler, it produces a dye which contributes to printing in the first color, and Produces a first diazonium salt that loses its activity when irradiated with light, and a dye that contributes to printing at least in a second color when reacted with the coupler, and is irradiated with second light having a wavelength different from that of the first light. Then, a recording layer containing a second diazonium salt that loses its activity, at least one kind of coupler, and a basic compound is provided on a support, and as the second diazonium salt, 4-diazo-4′-sec- It contained at least one selected from butyl diphenyl ether hexafluorophosphate and 4-diazo-4′-tert-butyldiphenyl ether hexafluorophosphate. Further, according to the photo-fixing type thermosensitive recording medium of the present invention, the first diazonium which reacts with the coupler to generate a dye contributing to printing in the first color and loses its activity when irradiated with the first light. A salt and a second diazonium salt that reacts with the coupler to produce a dye that contributes to printing at least in the second color, and loses activity when irradiated with a second light having a different wavelength from the first light; A recording layer comprising at least one coupler and a basic compound is provided on a support,
The first diazonium salt includes 4- (4′-methylphenylthio) -2,5-diethoxybenzenediazonium hexafluorophosphate, and the second diazonium salt is 4-diazo-4′-sec-butyldiphenyl ether. It contained at least one selected from hexafluorophosphate, 4-diazo-4′-tert-butyldiphenylether hexafluorophosphate, and 4-diazo-4′-n-butyldiphenylether hexafluorophosphate.

According to the present invention, since the second diazonium salt includes a diazonium salt that loses its activity due to light having a wavelength shorter than 330 nm, the activity of the second diazonium salt is maintained, for example, in a room or in a car. You. Further, the first light for deactivating the first diazonium salt has a wavelength of 3
When the light of 30 nm or more is used, the activity of the second diazonium salt is maintained even in the first light irradiation treatment for fixing the printing of the first color. Therefore, it is a light-fixing type thermosensitive recording medium having a single recording layer and capable of multicolor printing, and the second color after the printing of the first color is completed.
Thus, even if the time required for printing with the color is long, it is possible to realize a light-fixing type thermosensitive recording medium in which the coloring ability of the second color is not substantially impaired.

According to the present invention, the recording layer can be a single layer. Therefore, the production of the medium becomes easier as compared with the optical fixing type thermosensitive recording medium in which the recording layer is of the laminated type, so that an inexpensive optical fixing type thermosensitive recording medium can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an absorption spectrum of 4-diazo-4′-n-butyldiphenyl ether hexafluorophosphate used as a second diazonium salt.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-40193 (JP, A) JP-A-7-276806 (JP, A) JP-A 8-118805 (JP, A) JP-A-6-118805 8621 (JP, A) JP-A-7-117352 (JP, A) JP-A-9-109559 (JP, A) JP-A-10-71771 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 5/28-5/34

Claims (4)

(57) [Claims] 1. A first diazonium salt which is encapsulated in a microcapsule, reacts with a coupler to produce a dye contributing to recording in a first color, and loses activity when irradiated with a first light. Reacts with the coupler to form a dye that contributes to recording at least in the second color, and loses activity when irradiated with a second light having a different wavelength from the first light A light-fixing type thermosensitive recording medium, comprising a recording layer comprising a second diazonium salt, at least one kind of coupler as the coupler, and a basic compound generating an atmosphere for causing each of the reactions, on a support. In the above, as the second diazonium salt, 4-diazo-4′-sec-butyldiphenylether hexafluorophosphate represented by the following formula (1) and the following (2) Indicated 4-diazo-4'-tert
A photo-fixable thermosensitive recording medium comprising at least one selected from butyl diphenyl ether hexafluorophosphate. Embedded image 2. A first diazonium salt which is encapsulated in a microcapsule, reacts with a coupler to produce a dye which contributes to recording in a first color, and loses activity when irradiated with a first light. Reacts with the coupler to form a dye that contributes to recording at least in the second color, and loses activity when irradiated with a second light having a different wavelength from the first light A light-fixing type thermosensitive recording medium, comprising a recording layer comprising a second diazonium salt, at least one kind of coupler as the coupler, and a basic compound generating an atmosphere for causing each of the reactions, on a support. In the above, as the first diazonium salt, 4- (4′-methylphenylthio) -2,5-diethoxybenzenediazonium hexafluorophosphate represented by the following formula (4): Wherein, as the second diazonium salt, the following (1) shown is 4-diazo-4'-sec-butyl ether hexafluorophosphate in formula, the following (2)-4'-tert are 4-diazo of formula
A photo-fixing type thermosensitive recording medium comprising at least one selected from butyl diphenyl ether hexafluorophosphate and 4-diazo-4'-n-butyldiphenyl ether hexafluorophosphate represented by the following formula (3). Embedded image 3. The light-fixing type heat-sensitive recording medium according to claim 1, wherein the at least one coupler is 2-hydroxy-3-naphthoic acid anilide represented by the following formula (5) and (6): N) (2-benzothiazolyl) represented by the formula:
An optical fixing type thermosensitive recording medium comprising two types of acetoacetamide couplers. Embedded image 4. The light-fixing type thermosensitive recording medium according to claim 1, wherein the at least one type of coupler includes 2-hydroxy-3-naphthoic acid anilide represented by the following formula (5). Characteristic light fixing type thermosensitive recording medium. Embedded image