JP3484007B2 - Thermal recording method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a multicolor thermosensitive recording material.
More specifically, it relates to a heat-sensitive recording method using a multicolor heat-sensitive recording material having excellent image quality uniformity and running property .
That on the heat-sensitive recording method.

[0002]

2. Description of the Related Art In image recording of a full-color heat-sensitive recording material, a thermal head directly makes contact with the surface of the recording material to perform thermal recording. Therefore, when the surface of the recording material has irregularities, image unevenness occurs. It has been found that the flatness of the recording material largely depends on the flatness of the support used.

Conventionally, as a support, a polyethylene-coated paper in which a polyethylene layer obtained by kneading a white pigment and the like is provided on a base paper manufactured from pulp is usefully used. However, when polyethylene-coated paper is used as a support, the uneven surface of the adjacent base paper results in a rough, rippled, glossy surface, which considerably impairs the uniformity of the image.

As a method for solving the above-mentioned drawbacks, some methods have been proposed in which a base paper is not used for a support and only a thermoplastic resin film is used. JP-A-49-114921
Japanese Patent Publication No. 55-5104 discloses a method of filling a polystyrene resin film with a white pigment. Further, British Patent Nos. 1,563,591 and 1,563,592 disclose a method of adding barium sulfate to polyester and stretching. Japanese Examined Sho 56
No. -4901 discloses a technique of using barium sulfate and titanium oxide as a thermoplastic resin. JP-A-61-1
No. 18746, polyester has an average particle size of 0.1 to 0.1
A technique of adding 0.5 μm surface-treated titanium oxide is disclosed. Since they are hard and brittle, they tend to have knicks and the like during handling, and they have the drawbacks of making them feel as rigid as plastics and having a greatly different texture compared to those obtained by melting and extruding a polyolefin resin on the base paper.

Further, Japanese Patent Application Laid-Open No. 49-12815 discloses a technique for forming a polyolefin layer containing a white inorganic filler on one side of a synthetic paper or a plastic film having writability. It is impossible to adjust the curl after coating.

Further, Japanese Patent Application Laid-Open No. 3-91740 discloses a type of support in which a paper, synthetic paper or film substrate is coated with a polyolefin resin composition containing a specific titanium oxide. The support has a smooth surface. However, it is not easy to handle.

Japanese Unexamined Patent Publication (Kokai) No. 2-230236 discloses a technique of laminating a polyolefin resin on the surface of a thermoplastic resin such as a vinyl chloride resin which is suitable for embossing for ID cards and cashing cards. Compared with a product obtained by melt-extruding a polyolefin resin, it has a drawback that it feels as rigid as a plastic sheet, the texture is greatly different, and the smoothness is insufficient.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks, which is excellent in image quality uniformity while maintaining the texture of a conventional support using a base paper.
Another object of the present invention is to provide a multicolor thermosensitive recording material having excellent running properties.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermosensitive recording method using a multicolor thermosensitive recording material in which two or more thermosensitive recording layers are provided on a support, wherein the support has resin layers on both sides of the base paper. The sheet-like substrate provided with the sheet-like substrate having a rigidity defined by JIS P8125 of 1.5 to 8.
This is achieved by a heat-sensitive recording method using a multicolor heat-sensitive recording material, characterized in that the direction of 0 gf · cm is the printing direction. Here, the printing direction means the direction in which the thermal recording material travels during printing. The rigidity described above is preferably
It is preferably from 3.0 to 6.0 gf · cm, and the resin layers provided on both sides of the base paper are preferably formed by melt extrusion coating or dry lamination of an olefin resin.

The present invention will be described in more detail below. The base paper used for the support for the multicolor thermosensitive recording material according to the present invention is selected from commonly used materials. That is, a natural pulp selected from softwood, hardwood, etc. is used as a main raw material, and if necessary, a filler such as clay, talc, calcium carbonate, urea resin fine particles, rosin, alkyl ketene dimer, higher fatty acid, epoxidized fatty acid amide, paraffin wax. A sizing agent such as alkenyl succinic acid, a starch, a paper-strengthening agent such as polyamide polyamine epichlorohydrin or polyacrylamide, a sulfuric acid band, a fixing agent such as a cationic polymer, and the like are used. Further, a softening agent such as an epoxidized fatty acid amide or a surfactant may be added. Further, synthetic pulp may be used in place of the above natural pulp, or natural pulp and synthetic pulp may be mixed in an arbitrary ratio.

The type and thickness of the base paper substrate are not particularly limited, but the basis weight is 60 g / m ^{2 to} 170.
Since g / m ² is desirable, and a multicolor heat-sensitive recording material is desired to have as high flatness as possible, it is desirable that it has excellent surface smoothness and flatness. Surface treatment is preferably performed by applying heat and pressure. The support for a multicolor heat-sensitive recording material of the present invention is preferably one in which a surface sizing agent is applied to both sides of a base paper. The surface size liquid is an aqueous solution of polyvinyl alcohol and / or its modified products, and other high molecular compounds such as starch, carboxymethyl cellulose, hydroxyethyl cellulose, sodium alginate, cellulose sulfate, gelatin, casein, calcium chloride, sodium chloride and sulfuric acid. Metal salts such as sodium, hygroscopic substances such as glycerin and polyethylene glycol, dyes, coloring such as fluorescent whitening agents, whitening substances, caustic soda, ammonia water, hydrochloric acid, sulfuric acid, sodium carbonate and other pH control agents are added. May be. Further, a softening agent such as an epoxidized fatty acid amide or a surfactant may be added. Further, a pigment or the like can be added if necessary. As a method for impregnating the base paper, it is preferable to impregnate and apply with a size press, a tab size or a gate roll coaster.

The base paper in the present invention is TAPPI US
The internal binding force defined by EFUL METHOD 403 is preferably 0.5 to 1.8 kgf · cm. When the internal binding force of the base paper is less than 0.5 kgf · cm, the strength of the base paper is lowered, papermaking and processing are likely to be difficult, and the running property of the printer when developing the color of the thermal recording material is still poor. is there. On the other hand, when the internal binding force of the base paper is larger than 1.8 kgf · cm, the smoothness of the base paper is poor, and even when the thermoplastic resin layer is formed on the base paper by melt extrusion, the surface smoothness of the thermoplastic resin layer is low. And the thermal recording layer surface provided on the thermoplastic resin layer is also inferior in smoothness, so that the thermal head does not hit the thermal recording layer uniformly, resulting in lack of image uniformity. Moreover, the internal binding force of the base paper is 1.8 kgf · cm.
If it is larger than the above, the compressibility in the thickness direction of the base paper becomes small, so that the compressibility in the thickness direction of the sheet-shaped substrate provided with a resin layer on both sides thereof and the thermal recording material provided with the thermal recording layer becomes small, Since the thermal head does not hit the heat-sensitive recording layer uniformly, the image quality is inferior.

Therefore, the TAP of the base paper in the present invention
When the internal binding force defined by PI USEFUL METHOD 403 is 0.5 to 1.8 kgf · cm, there is no hindrance to the papermaking process and the running property of the product, and the image uniformity in the product is excellent. Become. From this point, especially TAPPI USEFUL METHO of the base paper
Internal bond strength defined by D 403 is 0.5 to 1.6k
More preferably, it is gf · cm. As a means for controlling the above internal binding force in the base paper, it is desirable to select a pulp type, soften the pulp by beating, and adjust the Canadian freeness value. The Canadian freeness value indicates an index of softening of pulp. The smaller the Canadian freeness value, the more the beating and the larger the internal binding force.
Also, the internal binding force can be adjusted by adjusting the addition rate of the chemicals added to the pulp. For example, when the addition rate of sizing agents such as epoxidized fatty acid amides, alkyl ketene dimers, and fatty acid salts increases, the internal binding force decreases, while when the addition rate of paper strengthening agents such as polyacrylamide increases, internal binding Power increases. Therefore, the internal bond strength can be adjusted to a desired value by adjusting the addition rates of these chemicals.

The resin layer formed on both sides of the base paper may be a resin layer formed by melt extrusion coating on the base paper, or a resin layer formed by dry lamination, that is, previously formed. Alternatively, the thermoplastic resin film may be adhered to the base paper with an adhesive. The resin in the resin layer formed by melt extrusion coating on the base paper is preferably a polyolefin resin, for example, α such as polyethylene or polypropylene.
Mention may be made of homopolymers of olefins and mixtures of these various polymers. Particularly preferred polyolefins are high density polyethylene, low density polyethylene, and mixtures thereof. These polyolefins are
There is no particular limitation on the molecular weight of the raw material as long as it can be coated on the raw paper surface by melt extrusion, and therefore, a polyolefin having a molecular weight in the range of 10 ⁴ to 10 ⁶ is usually used.

When a preformed film of a thermoplastic resin is adhered to the base paper with an adhesive, an olefin resin is preferable, and for example, an α-olefin homopolymer such as polyethylene or polypropylene and various kinds of these. Although a mixture of the above polymers can be mentioned, polyethylene terephthalate and the like are particularly preferable. When a resin layer is provided as a back layer on the surface of the base paper opposite to the surface on which the heat-sensitive recording layer is provided, curl balance of the sheet-shaped substrate can be achieved. If the curl balance of the sheet-shaped substrate is poor, it also affects the curl after coating the heat-sensitive recording layer, which adversely affects the paper feeding property and running property of the printer.

It is preferable that the front surface, that is, the thermoplastic resin layer on the side on which the heat-sensitive recording layer is coated, contains a white pigment, and the kind and the amount of the white pigment are known. It can be appropriately selected from the above. Further, it is possible to add known additives such as a fluorescent whitening agent and an antioxidant. Examples of white pigments to be filled include titanium dioxide, barium sulfate, barium carbonate, calcium carbonate, lithopone, white alumina, zinc oxide, silica antimony trioxide, and titanium phosphate. These may be used alone or in combination. Among these, titanium dioxide and zinc oxide are particularly preferable from the viewpoint of whiteness, dispersibility and stability. Titanium dioxide may be rutile type or anatase type, and they may be used alone or in combination. Further, it may be made by the sulfuric acid method or the chlorine method. Titanium dioxide includes hydrated alumina treatment, hydrated silicon dioxide-based treatment, zinc oxide treatment or other surface coating treatment with an inorganic substance, trimethylolmethane, trimethylolethane, trimethylolpropane, 2,4-dihydroxy-2-methyl. It is possible to appropriately use a material whose surface is coated with an organic substance such as pentane or a material which is treated with siloxane such as polydimethylsiloxane. The filling amount of the white pigment in the thermoplastic resin layer varies depending on the thickness of the white pigment used and the thermoplastic resin layer, but is usually selected to be between 5% by weight and 20% by weight. As the extrusion coating equipment for extrusion coating a thermoplastic resin such as polyolefin, a usual polyolefin extruder and laminator are used.

Before the thermoplastic resin layer is extruded and coated on the base paper, it is preferable to pretreat the base paper in order to strengthen the adhesion between the base paper and the resin coating layer. As the pretreatment of the base paper, there are acid etching treatment with a mixed solution of chromic acid sulfate, flame treatment with gas flame, ultraviolet irradiation treatment, corona discharge treatment, glow discharge treatment, anchor coat treatment with alkyl titanate and the like, which can be freely selected. From the viewpoint of simplicity, corona treatment is convenient. In the case of corona treatment, it is necessary to treat so that the contact angle with water is 70 ° or less.

As the anchor coating agent, organic titanium type, isocyanate type (urethane type) polyethyleneimine type, polybutadiene type and the like are known. Specifically, as organic titanium-based materials, alkyl titanates such as tetraisopropyl titanate, tetrabutyl titanate and tetrastearyl titanate, titanium acylates such as butoxytitanium stearate, titanium chelates such as titanium acetylacetonate are known. . Further, as the isocyanate type (urethane type), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), xylylene diisocyanate (XD) is used.
I), isophorone diisocyanate (IPDI) and the like are known.

Further, in order to improve the adhesiveness between the thermoplastic resin coating layer such as polyolefin and the thermosensitive recording layer coated thereon, the surface of the thermoplastic resin layer is subjected to surface treatment such as corona discharge treatment. Alternatively, the surface of the thermoplastic resin layer may be subjected to corona discharge treatment, and an undercoat layer mainly containing gelatin may be provided.

The surface of the base paper opposite to the surface on which the heat-sensitive recording layer is formed, that is, the polyethylene layer on the back surface is usually a matte surface. It is possible to provide an antistatic layer containing an ionic organic antistatic agent such as an alkali metal salt of a polymerizable carboxylic acid, colloidal silica or the like on the polyethylene layer on the back surface thereof, if necessary.

In the present invention, the support is composed of a sheet-like substrate having resin layers formed on both sides of the base paper. This sheet-like substrate is required to have a rigidity defined by JIS P8125 of 1.5 to 8.0 gf · cm in the printing direction. The printing direction means the direction in which the thermal recording material runs during printing. FIG. 1 is an explanatory view showing a relationship between a sheet-shaped substrate and a printing direction of a multicolor heat-sensitive recording material.
In the multicolor heat-sensitive recording material, a band-shaped sheet-shaped substrate 11 having a heat-sensitive recording layer formed on one side of a sheet-shaped substrate is cut into a predetermined size according to the use or the like to form a recording paper 12.

In FIG. 1, for example, in the case of an A type recording paper, if the direction indicated by the arrow A in the drawing is the printing direction, the strip-shaped sheet substrate 11 is JIS P8125 in the A direction.
The rigidity defined by is 1.5 to 8.0 gf · cm,
In the case of the B type recording paper, if the direction indicated by the arrow B is the printing direction, the strip-shaped sheet substrate 11 is in the B direction according to JIS.
The rigidity defined by P8125 is 1.5 to 8.0 gf
It must be cm.

The sheet-like substrate tends to have higher rigidity as the thickness of the base paper increases, and tends to increase as the basis weight of the base paper increases. The rigidity tends to increase as the amount of LBSP increases. In addition, the influence on the stiffness increases in the order of thickness of base paper> basis weight of base paper> blending of pulp. Further, the thicker the resin layers formed on both sides of the base paper, the higher the rigidity. Therefore, the rigidity can be adjusted by arbitrarily selecting the thickness of the base paper, the basis weight of the base paper, the mixture of pulp, the thickness of the resin layer, and the like. For example, the thickness of the base paper is 50 to 160 μm, and the basis weight of the base paper is
60 to 170 g / m ² is preferable, and the thickness of the resin layer is 1
About 0 to 80 μm is preferable. Moreover, as shown in FIG. 1, since the stiffness is usually different between the vertical and the horizontal in the paper,
The purpose can be realized by utilizing the anisotropy. If the thickness of the resin layer is thinner than 10 μm and is thicker than 80 μm together with the adjustment of the rigidity, the stability of the melt extrusion extrusion coating at a high speed is insufficient, which is not preferable.

The sheet-like substrate is JIS in the printing direction.
If the rigidity defined by P8125 is less than 1.5 gf · cm, the running performance is poor, and if it is more than 8.0 gf · cm, the thermal head hits the thermal recording layer unevenly, resulting in an unsatisfactory image. Be uniform.

In order to improve the uniformity of the image, it is necessary that the sheet-like substrate for a multicolor heat-sensitive recording material produced by the above method has high smoothness, and the multicolor heat-sensitive recording layer is formed. The center surface average roughness (SRa) of the surface to be coated is 0.
5 μm or less is desirable, further 0.2 μm
The following is desirable.

The center surface roughness (SRa) is defined by extracting a portion having an area SM from the roughness curved surface and placing the orthogonal coordinate axes, the X axis and the Y axis on the center surface of the extracted portion. When the axis orthogonal to the surface is set as the Z axis, the value given by the following mathematical expression is defined as the center surface average roughness (SRa),
It is expressed in μm.

[0027]

[Equation 1]

However, the LX · LY = SM Z = f (X, Y) center plane average roughness is, for example, a radius of 2 μm using a three-dimensional surface shape measuring instrument (Surfcom 575A-3DF) manufactured by Tokyo Seimitsu Co., Ltd. 2mm or more and 0.4m with diamond needle
It can be determined by measuring the area of 400 mm ² under the condition that the wavelength of m or less is cut.

A support having excellent image uniformity can be obtained by coating a heat-sensitive recording layer on the support thus obtained as described later. The thermal recording layer will be described.

In FIG. 2, a transparent cyan heat-sensitive layer 22, an intermediate layer 23, a transparent yellow heat-sensitive layer 24 are formed on one surface of a support 21.
This is a multicolor thermosensitive recording material in which an intermediate layer 25 and a transparent magenta thermosensitive layer 26 are sequentially laminated and a transparent protective layer 27 is provided thereon. In this case, at least the magenta heat-sensitive layer and the yellow heat-sensitive layer have a color-developing system that is a diazo system, and the cyan heat-sensitive layer may or may not be a diazo system.
In this case, the diazo compound is selected so that its decomposition wavelength range is longer as it is used for the outer heat-sensitive layer.

For recording, first, the outermost heat-sensitive layer is colored with magenta at low heat energy, and then the diazo compound contained in the outermost heat-sensitive layer is decomposed by irradiating light in the decomposition wavelength range from the upper surface. To fix the recorded image on the outermost heat-sensitive layer.

Next, heat energy larger than that at the time of the above-mentioned thermal recording is applied to cause the second heat-sensitive layer to develop yellow color, and the second heat-sensitive layer is developed.
The recorded image of the second layer is fixed by irradiating light in the decomposition wavelength range of the diazo compound contained in the layer. Further, heat energy higher than that applied to the second layer is applied to cause the innermost heat-sensitive layer to develop cyan. If the innermost heat-sensitive layer also uses the diazo color development system, it is possible to irradiate light in the decomposition wavelength range to fix the recorded image in the innermost layer as well to prevent the occurrence of scumming over time. It is possible to do so, which is preferable.

As described above, since cyan, magenta, and yellow can be independently colored, as a result, cyan, magenta, yellow, cyan + magenta (blue), magenta + yellow (red ), Cyan + yellow (green), and cyan + magenta + yellow (black), a total of seven basic colors are realized with good color separation. In this case, those skilled in the art can easily understand that the innermost heat-sensitive layer does not adversely affect the color reproduction even if it is opaque.

If the outermost heat-sensitive layer has sufficient scratch resistance and sticking resistance, it goes without saying that the transparent protective layer may not be provided. Further, those skilled in the art can easily understand that the number of colors that can be realized by color mixing can be synergistically increased by controlling the color development of each unit by appropriately adjusting the applied heat energy. .

As described above, in the present invention, the coloring system of the innermost heat-sensitive layer may not be the diazo system. In this case, it is preferable to use a combination of an electron-donating dye precursor and a developer (leuco system) as a color-developing system other than the diazo system from the viewpoint of heat sensitivity and color density.

Next, the materials used for the multicolor thermosensitive recording material of the present invention will be described in detail. The electron-donating dye precursor in the present invention has a property of developing a color by donating an electron or accepting a proton such as an acid, and is not particularly limited, but it is usually substantially colorless and a lactone. Compounds having partial skeletons such as lactam, sultone, spiropyran, ester, amide, etc., and these partial skeletons are ring-opened or cleaved upon contact with a color developer are used. Specifically, crystal violet lactone, benzoyl leuco methylene blue, malachite green lactone,
Rhodamine B lactam, 1,3,3-trimethyl-6 '
-Ethyl-8'-butoxyindolinobenzospiropyran and the like.

The color developer for these color formers can be appropriately selected and used from known ones. For example, the developer for the leuco dye includes a phenol compound, a sulfur-containing phenol compound, a carboxylic acid compound, a sulfone compound, a urea compound or a thiourea compound, and the details thereof are, for example, Paper Pulp Technology Times. (1
985) 49-54 and 65-70. Among these, those having a melting point of 50 ° C. to 250 ° C. are particularly preferable, and among them, phenol and organic acids having poor solubility in water of 60 ° C. to 200 ° C. are preferable. When two or more developers are used in combination, the solubility increases, which is preferable.

Among the color developers used in the present invention, particularly preferable ones are represented by the following general formulas (1) to (4).

General formula (1)

[Chemical 1] m = 0-2, n = 2-11

General formula (2)

[Chemical 2] R ⁷ is an alkyl group, an aryl group, an aryloxyalkyl group or an aralkyl group, and a methyl group and a butyl group are particularly preferable.

General formula (3)

[Chemical 3] R ⁸ is an alkyl group, especially a butyl group, a pentyl group,
Heptyl and octyl groups are preferred. R ⁹ is a hydrogen atom or a methyl group, and n is 0-2.

General formula (4)

[Chemical 4] R ¹⁰ is an alkyl group, an aralkyl group or an aryloxyalkyl group.

In the present invention, 0.3 to 160 parts by weight of a color developer is added to 1 part by weight of the electron-donating dye precursor.
It is preferable to use 0.3 to 80 parts by weight.

The other diazo compound of the color-forming material of the multicolor heat-sensitive recording material of the present invention is a compound which reacts with a developer called a coupler described later to develop a desired hue, and before reaction. When it receives light of a specific wavelength, it decomposes and after that the coupler no longer has the ability to develop color.

The hue in this color forming system is mainly determined by the diazo dye formed by the reaction of the diazo compound and the coupler. Therefore, as is well known, the coloring hue can be easily changed by changing the chemical structure of the diazo compound or the chemical structure of the coupler, and almost any coloring hue can be obtained depending on the combination. .

The photodecomposable diazo compound in the present invention mainly refers to an aromatic diazo compound, more specifically, a compound such as an aromatic diazonium salt, a diazosulfonate compound, a diazoamino compound or the like. Hereinafter, a diazonium salt will be mainly described as an example.

It is generally said that the photolysis wavelength of a diazonium salt is its absorption maximum wavelength. The absorption maximum wavelength of the diazonium salt is 200n depending on its chemical structure.
It is known to change from the m-position to the 700-nm position ("Photolysis and chemical structure of photosensitive diazonium salts" by Takahiro Tsunoda and Ao Yamaoka, Journal of the Photographic Society of Japan 29 (4) 197-1.
05 (1965)). Further, by changing the chemical structure of the diazonium salt, the hue of the dye produced by the coupling reaction can be changed even when the coupling reaction with the same coupler is performed.

The diazonium salt of the general formula ArN ₂ ⁺ X ^- is a compound represented by. In the formula, Ar represents a substituted or unsubstituted aromatic moiety, N ₂ ⁺ represents a diazonium group, and X ⁻ represents an acid anion.

Of these, compounds having a photolytic wavelength near 400 nm include 4-diazo-1-dimethylaminobenzene, 4-diazo-1-diethylaminobenzene, 4-diazo-1-dipropylaminobenzene, 4-diazo-1-diethylaminobenzene.
Diazo-1-methylbenzylaminobenzene, 4-diazo-1-dibenzylaminobenzene, 4-diazo-1-
Ethylhydroxyethylaminobenzene, 4-diazo-
1-diethylamino-3-methoxybenzene, 4-diazo-1-dimethylamino-2-methylbenzene, 4-diazo-1-benzoylamino-2,5-diethoxybenzene, 4-diazo-1-morpholinobenzene, 4 -Diazo-1-morpholino-2,5-dibutoxybenzene, 4
-Diazo-1-anilinobenzene, 4-diazo-1-toluylmercapto-2,5-diethoxybenzene, 4-
Diazo-1,4-methoxybenzoylamino-2,5-
Diethoxybenzene etc. can be mentioned.

The compounds having a photolytic wavelength in the range of 300 to 370 nm include 1-diazo-4- (N, N-dioctylcarbamoyl) benzene, 1-diazo-2-octadecyloxybenzene, 1-diazo-4- (4. -Tert
-Octylphenoxy) benzene, 1-diazo-4-
(2,4-Di-tert-amylphenoxy) benzene, 1-diazo-2- (4-tert-octylphenoxy) benzene, 1-diazo-5-chloro-2- (4-
tert-octylphenoxy) benzene, 1-diazo-2,5-bis-octadecyloxybenzene, 1-diazo-2,4-bis-octadecyloxybenzene, 1
-Diazo-4- (N-octyltheuroylamino) benzene and the like can be mentioned. The aromatic diazonium compounds represented by the above-mentioned examples can widely change the photolysis wavelength by arbitrarily changing the substituents.

Specific examples of the acid anion include C _n F _{2n + 1}
COO ⁻ (n represents 3 to 9), C _m F _{2m + 1} SO ₃ ⁻
(M represents 2 to 8), (ClF _{2i + 1} SO ₂ ) ₂ CH
^- (I represents 1 to 18),

[0052]

[Chemical 5]

Specific examples of the diazo compound (diazonium salt) include the followings.

[0054]

[Chemical 6]

[0055]

[Chemical 7]

The diazosulfonate compound that can be used in the present invention has the general formula

[0057]

[Chemical 8]

Is a compound represented by: In the formula, R ₁ is an alkali metal or ammonium compound, R ₂ , R ₃ , R ₅
And R ₆ is hydrogen, halogen, an alkyl group, or an alkoxy group, and R ₄ is hydrogen, a halogen, an alkyl group, an amino group, a benzoylamide group, a morpholino group, a trimercapto group, or a pyrrolidino group.

Many such diazosulfonates are known, and they can be obtained by treating each diazonium salt with sulfite.

Of these compounds, preferred compounds are 2-methoxy, 2-phenoxy and 2-methoxy-
4-phenoxy, 2,4-dimethoxy, 2-methyl-4
A benzenediazosulfonate having a substituent such as -methoxy, 2,4-dimethyl, 2,4,6-trimethyl, 4-phenyl, 4-phenoxy, 4-acetamide, or 4- (N-ethyl, N-benzylamino), 4-
(N, N-Dimethylamino), 4- (N, N-diethylamino), 4- (N, N-diethylamino) -3-chloro, 4-pyridinino-3-chloro, 4-morpholino-2
-Methoxy, 4- (4'-methoxybenzoylamino)
-2,5-dibutoxy, 4- (4'-trimercapto)
It is a benzenediazosulfonate having a substituent such as -2,5-dimethoxy. When using these diazosulfonate compounds, it is desirable to perform light irradiation for activating the diazosulfonate before printing.

As another diazo compound which can be used in the present invention, a diazoamino compound can be mentioned. As the diazoamino compound, a diazo group having a dicyandiamide, sarcosine, methyltaurine, N-ethylanthranic acid-5-sulphonic acid,
It is a compound coupled with monoethanolamine, diethanolamine, guanidine and the like.

The coupler used in the present invention forms a dye by coupling with a diazo compound (diazonium salt), and specific examples thereof include resorcin, phloroglucin and sodium 2,3-hydroxynaphthalene-6-sulfonate. , 1-hydroxy-2-naphthoic acid morpholinopropylamide, 1,5-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,3-dihydroxy-6-sulfanylnaphthalene, 2-hydroxy-3-naphthoic acid morpholinopropylamide, 2-Hydroxy-3-naphthoic acid-2'-methylamide, 2-hydroxy-3-naphthoic acid ethanolamide, 2-hydroxy-3-naphthoic acid octylamide, 2-hydroxy-3-naphthoic acid-N-dodecyl-oxy -Propylamide, 2-hydroxy Ci-3-naphthoic acid tetradodecylamide, acetanilide, acetoacetalinide, benzoylacetanilide, 1-phenyl-3-methyl-
5-pyrazolone, 2,4-bis (benzoylacetamino) toluene, 1,3-bis (bivaloylacetaminomethyl) benzene, 1- (2 ', 4', 6'-trichlorophenyl) -3-benzamide- 5-pyrazolone, 1
Examples thereof include-(2 ', 4', 6'-trichlorophenyl) -3-anilino-5-pyrazolone and 1-phenyl-3-phenylacetamido-5-pyrazolone.

Further, by using two or more of these couplers in combination, an image of any color tone can be obtained. Since the coupling reaction between these diazo compound and the coupler easily occurs in a basic atmosphere, a basic substance may be added in the layer.

As the basic substance, a slightly water-soluble or water-insoluble basic substance and a substance which generates an alkali upon heating are used. Examples thereof are inorganic and organic ammonium salts, organic amines, amides, urea and thiourea and their derivatives, thiazoles, pyrroles, pyrimidines, piperazines, guanidines, indoles, imidazoles, imidazolines and triazoles. , Nitrogen-containing compounds such as morpholines, piperidines, amidines, formazines and pyridines. Specific examples of these are described, for example, in Japanese Patent Application No. 60-132990. Two or more basic substances may be used in combination.
The coupler is 0.1-10 with respect to 1 part by weight of the diazo compound.
It is preferable to use 0.1 part by weight and 20 parts by weight of the basic substance.

The materials which cause the above-mentioned color-developing reaction are made from the viewpoint of improving the transparency of the heat-sensitive layer, the viewpoint of raw storability such as preventing contact between the color-developing agent and the color-developing agent at room temperature (prevention of fog), and the desired heat From the viewpoint of controlling the color development sensitivity such that energy is used for color development, it is preferable to encapsulate some of the components essential for color development.

The type of microcapsules used in this case is not particularly limited, but the microcapsules particularly preferred in the present invention prevent contact between substances inside and outside the capsules at room temperature due to the substance separating action of the microcapsule walls. The permeation of a substance increases only while it is heated above a certain temperature, and the permeation initiation temperature can be freely controlled by appropriately selecting the capsule wall material, the capsule core substance, and the additive. It is a thing.
The permeation initiation temperature in this case corresponds to the glass transition temperature of the capsule wall (eg, JP-A-59-91438).
Japanese Patent Application No. 59-190886, Japanese Patent Application No. 59-994.
No. 90).

In order to control the glass transition point specific to the capsule wall, it is necessary to change the type of capsule wall forming agent. As the wall material of the microcapsule, polyurethane, polyurea, polyester, polycarbonate, urea-formaldehyde resin, melamine resin, polystyrene, styrene methacrylate copolymer, styrene-acrylate copolymer, gelatin, polyvinylpyrrolidone,
Examples thereof include polyvinyl alcohol. In the present invention, two or more of these polymer substances may be used in combination. In the present invention, among the above polymeric substances, polyurethane, polyurea, polyamide, polyester, polycarbonate and the like are preferable, and polyurethane and polyurea are particularly preferable.

The microcapsules used in the present invention can be microencapsulated by emulsifying a core substance containing a reactive substance such as a color former and then forming a wall of a polymer substance around the oil droplets. Preferably, in this case the reactant forming the polymeric substance is added inside the oil droplet and / or outside the oil droplet. Details of the microcapsules that can be preferably used in the present invention, such as the preferred method for producing the microcapsules, are described in, for example, JP-A-59-222716.

Here, the organic solvent for forming the oil droplets can be appropriately selected from high boiling point oils in general, and particularly, an organic solvent suitable for dissolving the developer or coupler described later. The use of is preferred because it has excellent solubility in a color former and can increase the color density and color development rate in thermal printing or reduce fog. When making microcapsules, it can be made from an emulsion containing 0.2% by weight or more of the components to be microencapsulated.

The preferred microcapsules produced as described above are not destroyed by heat or pressure as used in conventional recording materials, and the reactive substance contained in the core and outside of the microcapsules is It can react through the walls of the microcapsules.

In the present invention, it is also possible to use a color forming aid. The color-forming aid that can be used in the present invention is a substance that increases the color-developing density during heating printing or lowers the minimum color-forming temperature, such as a coupler, a basic substance, a color-developing agent, a developer or a diazo compound. The effect is to lower the melting point of or to lower the softening point of the capsule wall, thereby creating a situation in which diazo, a basic substance, a coupler, a color developing agent, a color developing agent and the like are likely to react.

Examples of the color-forming assistant include phenol compounds, alcoholic compounds, amide compounds, sulfonamide compounds and the like. Specific examples are p-tert-octylphenol, p-benzyloxyphenol, phenyl p-oxybenzoate, Benzyl carbanylate, phenethyl carbanylate, hydroquinone dihydroxyethyl ether, xylylenediol, N-hydroxyethyl-
Examples thereof include compounds such as methanesulfonic acid amide and N-phenyl-methanesulfonic acid amide. These may be contained in the core substance or may be added outside the microcapsules as an emulsified dispersion.

In the present invention, in order to obtain a substantially transparent thermosensitive color developing layer, the developer for the electron-donating dye precursor or the coupler for the diazo compound is dissolved in a water-insoluble or insoluble organic solvent. After that, this is mixed with an aqueous phase containing a surfactant and having a water-soluble polymer as a protective colloid, and used in the form of an emulsion-dispersed dispersion.

The organic solvent that dissolves the color developer or coupler can be appropriately selected from high boiling point oils. Particularly, it is known as esters and pressure-sensitive oils, and it has two or more benzene rings and has a hetero atom. It is preferable that the number of oils is less than the specified number. Such oils include compounds represented by the following general formulas (5) to (7) and triallylmethane (eg, tritoluylmethane, toluyldiphenylmethane), terphenyl compounds, alkyl compounds (eg, terphenyl), alkylated They are diphenyl ether (for example, propyl diphenyl ether), hydrogenated terphenyl (for example, hexahydroterfel), and diphenyl ether. Above all, it is preferable to use the esters from the viewpoint of the emulsion stability of the emulsified dispersion of the color developer or the coupler.

General formula (5)

[Chemical 9] In the formula, R ¹ is hydrogen or an alkyl group having 1 to 18 carbon atoms, R ^1
2 represents an alkyl group having 1 to 18 carbon atoms. p ¹ , q ¹
Represents an integer of 1 to 4, and the total sum of alkyl groups is 4 or less. The alkyl group of R ¹ and R ² has 1 to 1 carbon atoms.
An alkyl group of 8 is preferred.

General formula (6)

[Chemical 10] In the formula, R ³ is hydrogen or an alkyl group having 1 to 12 carbon atoms, R ^3
4 represents an alkyl group having 1 to 12 carbon atoms. n represents 1 or 2. p ² and q ² represent an integer of 1 to 4. n =
In the case of 1, the total number of alkyl groups is 4 or less, and n
= 2, the total number of alkyl groups is 6 or less.

General formula (7)

[Chemical 11] In the formula, R ⁵ and R ⁶ represent a hydrogen atom or the same or different alkyl group having 1 to 18 carbon atoms. m represents an integer of 1 to 13. p ³ and q ³ represent an integer of 1 to 3, and
The total number of alkyl groups is 3 or less. The alkyl group of R ⁵ and R ⁶ is particularly preferably an alkyl group having 2 to 4 carbon atoms.

Examples of the compound represented by the formula (5) include dimethylnaphthalene, diethylnaphthalene and diisopropylnaphthalene.

Examples of the compound represented by the formula (6) include dimethylbiphenyl, diethylbiphenyl, diisopropylbiphenyl and diisobutylbiphenyl.

As an example of the compound represented by the formula (7), 1
-Methyl-1-dimethylphenyl-1-phenylmethane, 1-ethyl-1-dimethylphenyl-1-phenylmethane, 1-propyl-1-dimethylphenyl-1-phenylmethane.

Examples of the esters include phosphoric acid esters (eg, triphenyl phosphate, tricresyl phosphate, butyl phosphate, octyl phosphate, cresyl diphenyl phosphate), phthalic acid esters (dibutyl phthalate, 2-ethylhexyl phthalate, phthalic acid). Ethyl, octyl phthalate, butylbenzyl phthalate), tetrahydrophthalate dioctyl, benzoic acid ester (ethyl benzoate, propyl benzoate, butyl benzoate, isopentyl benzoate, benzyl benzoate), abietic acid ester (abietic acid) Ethyl, benzyl abietic acid), dioctyl adipate, isodecyl succinate, dioctyl azelate, oxalate ester (dibutyl oxalate, dipentyl oxalate), diethyl malonate, maleate ester (dimethyl maleate, maleic acid) Diethyl acid, dibutyl maleate), tributyl citrate, sorbate (methyl sorbate, ethyl sorbate, butyl sorbate), sebacate (dibutyl sebacate, dioctyl sebacate), ethylene glycol esters (formic acid monoester) And diesters, butyric acid monoesters and diesters, lauric acid monoesters and diesters, palmitic acid monoesters and diesters, stearic acid monoesters and diesters, oleic acid monoesters and diesters), triacetin, diethyl carbonate, diphenyl carbonate, ethylene carbonate, carbonic acid propylene,
Examples thereof include boric acid esters (tributyl borate, tripentyl borate) and the like. The above oils can be used together or with other oils.

In the present invention, an auxiliary solvent may be added to the above organic solvent as a dissolution aid having a low boiling point. As such an auxiliary solvent, for example, ethyl acetate, isopropyl acetate, butyl acetate, methylene chloride and the like can be mentioned as particularly preferable ones.

The water-soluble polymer to be contained as a protective colloid in the aqueous phase mixed with the oil phase in which the developer or coupler is dissolved is a known anionic polymer, nonionic polymer,
Although it can be appropriately selected from the amphoteric polymers, polyvinyl alcohol, gelatin, cellulose derivatives and the like are preferable.

As the surfactant to be contained in the aqueous phase, an anionic or nonionic surfactant which does not cause precipitation or aggregation by acting on the protective colloid is appropriately selected and used. be able to. Preferable surfactants include sodium alkylbenzene sulfonate (for example, sodium lauryl sulfate), dioctyl sodium sulfosuccinate, polyalkylene glycol (for example, polyoxyethylene nonylphenyl ether) and the like.

The emulsified dispersion of the developer or coupler in the present invention is usually prepared by high speed stirring, ultrasonic dispersion, etc. of an oil phase containing the developer or the coupler and an aqueous phase containing the protective colloid and the surfactant. It can be easily obtained by mixing and dispersing using the means used for fine particle emulsification.

At this time, the oil droplet size (diameter) of the emulsified dispersion
Is 7 to obtain a transparent heat-sensitive phase having a haze of 60% or less.
It is preferably μ or less. More preferably 0.1
It is within the range of 5μ.

Or the ratio of oil phase to water phase (oil phase weight /
The water phase weight) is preferably 0.02 to 0.6, and more preferably 0.1 to 0.4. If it is 0.02 or less, the amount of the aqueous phase is too large to be diluted, and sufficient color developability cannot be obtained.

In the present invention, in addition to the above materials, citric acid, tartaric acid, oxalic acid, boric acid, phosphoric acid, pyrophosphoric acid and the like can be added as an acid stabilizer.

The heat-sensitive material of the present invention can be coated using a suitable binder. As the binder, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, arabic rubber, gelatin, polyvinyl pyrrolidone, casein, styrene-butadiene latex, acrylonitrile-butadiene latex, polyvinyl acetate, polyacrylic acid ester, ethylene-vinyl acetate copolymer. It is possible to use various emulsions such as The amount used is 0.5 to 5 g / m ² in terms of solid content.

The coating amount of the heat sensitive layer is 3 g / m ^{2 to} 20.
g / m ^2, it is preferable that particularly is between ^{5g / m 2 ~15g / m 2} . If it is 3 g / m ² or less, sufficient sensitivity cannot be obtained, and even if it is coated at 20 g / m ² or more, no improvement in quality can be seen, which is disadvantageous in terms of cost. In the present invention, it is preferable to provide an intermediate layer between the heat-sensitive layer and the heat-sensitive layer from the viewpoints of raw storability of the heat-sensitive recording material, recorded image storability and improvement of color separation. It is preferable to use a layer in which the polymer is gelled with a polyvalent cation.

The water-soluble polyanionic polymer is preferably a polymer having a carboxyl group, a sulfonic acid group or a phosphoric acid group, and a water-soluble polyanionic polymer having a carboxyl group is particularly preferable. Examples of preferred water-soluble polyanionic polymers include natural or synthetic polysaccharide gums (such as alkali metal alginate,
Gua gum, gum arabic, carrageenan, pectin, tragacanth gum, xanthene gum, etc.), polymers of acrylic acid or methacrylic acid and copolymers thereof, polymers of maleic acid or phthalic acid and copolymers thereof, and cellulose derivatives such as carboxymethyl cellulose. , Gelatin, agar, etc., among which alkali metal alginate is preferable. The water-soluble polyanionic polymer has a molecular weight of 5,000.
0 to 10,000 is preferable, and particularly 10,000 from the viewpoints of barrier properties and production suitability aimed at in the present invention.
-40,000 is preferable. Examples of the polyvalent cation include salts of alkaline earth metals and other polyvalent metals (for example, CaC).
l ₂ , BaCl ₂ , Al ₂ (SO ₄ ) ₃ , ZnSO ₄
Etc.), polyamines (for example, ethylenediamine, diethylenetriamine, hexamethylenediamine, etc.) and polyimines are preferable.

Other preferable examples of the intermediate layer in the invention include an ion complex of a water-soluble polyanionic polymer and a water-soluble polycationic polymer. In this case, the various water-soluble polyanion polymers described above can be used as the water-soluble polyanion polymer.

As the water-soluble polycationic polymer, proteins having a plurality of reactive nitrogen-containing cationic groups, polypeptides such as polylysine, polyvinylamines, polyethyleneamines, polyethyleneimines and the like are preferable.

When the intermediate layer is prepared using these materials, either the water-soluble polyanionic polymer or the polyvalent cation is used to prevent the rapid gelation during coating from being applied to any of the heat-sensitive layers adjacent to each other. It is preferable to apply by incorporating it into one of the heat-sensitive layers, but the temperature should be p
It is also possible to adjust H or to include the one material in the adjacent heat-sensitive layer. Preferred coating weight of the intermediate layer is ^{0.05g / m 2 ~5g / m 2} , more preferably from ^{0.1g / m 2 ~2g / m 2} .

In the heat-sensitive layer of the present invention, at least the outermost heat-sensitive layer and the second heat-sensitive layer are required to be substantially transparent in order to improve color separation. The term “substantially transparent” as used herein means haze (%) (manufactured by Nippon Seimitsu Kogyo Co., Ltd., integrating sphere method H).
It must be 60% or less if expressed by a TR meter). It is preferably 40% or less, more preferably 30% or less. However, the actual transparency of the heat-sensitive layer test sample is greatly affected by light scattering due to fine irregularities on the surface of the heat-sensitive layer. Therefore, the transparency peculiar to the heat-sensitive layer to be a problem in the present invention, that is, when the transparency inside the heat-sensitive layer is measured by a haze meter, a transparent adhesive tape is attached onto the heat-sensitive layer as a simple method, Evaluation is performed by the value measured with surface scattering almost excluded. The transparency as described above can be easily achieved by using a color developer or a coupler in the form of the emulsified dispersion.

On the outermost heat-sensitive layer of the heat-sensitive recording material of the present invention, it is preferable to substantially provide a protective layer for improving scratch resistance and preventing sticking. Two or more protective layers may be laminated. The transparent protective layer that can be used in the present invention comprises at least silicon-modified polyvinyl alcohol and colloidal silica.

The above silicon-modified polyvinyl alcohol is
It is not particularly limited as long as it contains a silicon atom in the molecule, but usually a silicon atom contained in the molecule is an ercoxyl group, an acyloxyl group or a hydroxyl group or its alkali metal salt obtained by hydrolysis or the like. It is preferable to use those having a reactive substituent of.
Details of such a method for producing a modified polyvinyl alcohol containing a silicon atom in the molecule are described in JP-A-58-193189.
It is described in Japanese Patent Publication No.

The colloidal silica used in the present invention is used as a colloidal solution in which ultrafine particles of silicic acid anhydride are dispersed in water with water as a dispersion medium. The particles of colloidal silica have a size of 10 mμ to 100 mμ and a specific gravity of 1.1 to 1.
3 is preferable. In this case, a colloidal solution having a pH value of about 4 to about 10 is preferably used.

When the protective layer is provided on the surface of the heat-sensitive recording material, the surface scattering phenomenon is suppressed as in the case where the transparent adhesive tape is applied, and surprisingly, the transparency of the protective layer is very good. Is. Moreover, since the mechanical strength of the surface of the heat-sensitive layer is improved, the transparency of the whole heat-sensitive material can be further improved.

A suitable blending ratio of the silicon-modified polyvinyl alcohol and colloidal silica in the present invention is 0.5 to 3 parts by weight, more preferably 1 to 1 part by weight of silicon-modified polyvinyl alcohol.
2 parts by weight. If the amount of colloidal silica used is less than 0.5 parts by weight, the effect of improving transparency is small, and if it is used in an amount of 3 parts by weight or more, the protective layer film is cracked and the transparency is rather lowered.

The transparent protective layer may further contain one or more polymers. Specific examples of the polymer that can be used in combination include methyl cellulose, carboxymethyl cellulose,
Hydroxymethyl cellulose, starch, gelatin, gum arabic, casein, styrene-maleic anhydride copolymer hydrolyzate, styrene-maleic anhydride half ester hydrolyzate, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, polyacrylamide derivative , Water-soluble polymers such as polyvinylpyrrolidone, sodium polystyrene sulfonate and sodium alginate, and styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, methyl acrylate-
Examples thereof include water-insoluble polymers such as butadiene rubber latex and polyvinyl acetate emulsion. The amount used in combination is preferably 0.01 to 0.5 parts by weight with respect to 1 part by weight of silicon-modified polyvinyl alcohol.

Pigments, metal soaps, waxes, cross-linking agents and the like are added to the protective layer for the purpose of improving matching with a thermal head during thermal printing and improving water resistance of the protective layer.

The pigment has a refractive index of 1.4 to 1.55 and a particle size of 1 μm.
The following pigments are preferred. Specific examples thereof include calcium carbonate, talc, sekiseki, kaolin, aluminum hydroxide, and amorphous silica, and the addition amount thereof is 0.05 to 0.5 times the total weight of the polymer, particularly preferably 0.1. ~ 0.3 times the amount. When the amount is 0.05 times or less, it is ineffective for improving the matching property with the head, and when the amount is 0.5 times or more, the transparency and sensitivity of the heat-sensitive recording material are remarkably deteriorated and the commercial value thereof is impaired.

Examples of the metal soap include emulsions of higher fatty acid metal salts such as zinc stearate, calcium stearate and aluminum stearate, which are contained in an amount of 0.5 to 20% by weight, preferably 1 to 10% by weight based on the total weight of the protective layer. Added in quantity.

Examples of waxes include emulsions such as paraffin wax, microcrystalline wax, carnauba wax, methyl roll stearamide, polyethylene wax, and silicone, and the total weight of the protective layer is 0.5 to 40.
%, Preferably 1 to 20% by weight.

A surfactant is added to the coating solution for forming the protective layer in order to form the protective layer uniformly on the heat-sensitive layer. Surfactants include sulfosuccinic acid-based alkali metal salts, fluorine-containing surfactants, and the like.
Examples include sodium salts or ammonium salts of (2-ethylhexyl) sulfosuccinic acid, di- (n-hexyl) sulfosuccinic acid, and the like. Further, in the protective layer, a surfactant, a polymer electrolyte or the like for preventing the heat-sensitive recording material from being charged may be added.

The solid coating amount of the protective layer is usually 0.2 to 5 g.
/ M ² is preferable, and more preferably 1 to 3 g / m ² .

In the present invention, an undercoat layer may be provided between the two layers in order to enhance the adhesion between the support and the heat sensitive layer. As a material for the undercoat layer, gelatin, synthetic polymer latex, nitrocellulose or the like is used. The coating amount of the undercoat layer is preferably in the range of ^{0.1g / m 2 ~2.0g / m 2} , preferably in the range particularly ^{0.2g / m 2 ~1.0g / m 2} . If the amount is less than 0.1 g / m ² , the adhesion between the support and the heat-sensitive layer is not sufficient, and even if the amount exceeds 2.0 g / m ² , the adhesion between the support and the heat-sensitive layer reaches saturation. Therefore, there is a cost disadvantage.

When the heat-sensitive layer is coated on the undercoat layer, the image quality recorded on the heat-sensitive layer may be deteriorated if the water contained in the coating solution swells the undercoat layer. It is desirable to cure with a hardener. The following hardeners can be used in the present invention.

(1) Divinisulfone-N, N'-ethylenebis (vinylsulfonylacetamide), 1,3-bis (vinylsulfonyl) -2-propanol, methylene bismaleimide, 5-acetyl-1,3-di Acryloyl-hexahydro-s-triazine, 1,3,5-triacryloyl-hexahydro-s-triazine, 1,3,3
Active vinyl compounds such as 5-trivinylsulfonyl-hexahydro-s-triazine.

(2) 2,4-dichloro-6-hydroxy-s-triazine sodium salt, 2,4-dichloro-
6-methoxy-s-triazine, 2,4-dichloro-6
-(4-sulfoanilino) -s-triazine sodium salt, 2,4-dichloro-6- (2-sulfoethylamino) -s-triazine, N-N'-bis (2-chloroethylcarbamyl) piperazine Active halogen compounds such as.

(3) Bis (2,3-epoxypropyl)
Methylpropylammonium p-toluenesulfonate, 1,4-bis (2 ′, 3′-epoxypropyloxy) butane, 1,3,5-triglycidyl isocyanurate, 1,3-diglycidyl-5- (γ -Acetoxy-
Epoxy compounds such as β-oxypropyl) isocyanurate.

(4) Ethyleneimino compounds such as 2,4,6-triethylene-s-triazine, 1,6-hexamethylene-NN′-bisethyleneurea and bis-β-ethyleneiminoethylthioether.

(5) Methanesulfonic acid ester compounds such as 1,2-di (methanesulfonoxy) ethane, 1,4-di (methanesulfonoxy) butane, and 1,5-di (methanesulfonoxy) pentane.

(6) dicyclohexylcarbodiimide,
1-cyclohexyl-3- (3-trimethylaminopropyl) carbodiimide-p-toluenesulfonate, 1
Carbodiimide compounds such as ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride.

(7) 2,5-Dimethylisoxazole perchlorate, 2-ethyl-5-phenylisoxazole-3'-sulfonate, isoxazole such as 5,5 '-(paraphenylene) bisisoxazole Compounds.

(8) Chromium Inorganic compounds such as alum and chromium acetate.

(9) Dehydrated condensed peptide reagents such as N-carbethoxy-2-isopropoxy-1,2-dihydroquinoline and N- (1-morpholinocarboxy) -4-methylpyridinium chloride; N, N'- Active ester compounds such as adipoyldioxydisuccinimide and N, N'-terephthaloyldioxydisuccinimide.

(10) Isocyanates such as toluene-2,4-diisocyanate and 1,6-hexamethylene diisocyanate.

(11) Glutaraldehyde, glyoxal, dimethoxyurea, 2,3-hydroxy-1,4-
Dialdehydes such as dioxane.

Of these, glutaraldehyde,
Dialdehydes such as 2,3-dihydroxy-1,4-dioxane and boric acid are preferred.

The addition amount of these hardeners is in the range of 0.20% by weight to 3.0% by weight based on the weight of the undercoat material, and the addition amount is appropriate according to the coating method and the desired degree of curing. You can choose. If the added amount is less than 0.20% by weight, the degree of curing will be insufficient no matter how much the material is aged and the undercoat layer will swell when the heat-sensitive layer is applied. On the other hand, if the amount is more than 3.0% by weight, the degree of curing will be too advanced and the adhesion between the undercoat layer and the support will be rather deteriorated, and the undercoat layer will become a film and peel off from the support. . Depending on the curing agent used, if necessary, caustic soda or the like may be further added to bring the pH of the solution to the alkaline side, or the pH of the solution may be brought to the acidic side with citric acid or the like.

It is also possible to add an antifoaming agent to eliminate bubbles generated during coating, or to add an activator to improve the leveling of the liquid and prevent the generation of coating streaks. . Further, an antistatic agent can be added if necessary. Further, a white pigment may be added to the undercoat layer to make it opaque.

Before applying the undercoat layer, it is desirable to activate the surface of the support by a known method. As the activation method, etching treatment with acid, flame treatment with a gas burner, corona discharge treatment, glow discharge treatment, or the like is used, but from the viewpoint of cost or simplicity, US Pat. No. 075, No. 2, 8
No. 46,727, No. 3,549,406, No. 3,
The corona discharge treatment described in, for example, No. 590,107 is most preferably used.

The coating solution according to the present invention is generally well known, for example, dip coating method, air knife coating method, curtain coating method, roller coating method, doctor coating method, wire bar coating method, slide coating method, Gravure coating method or US Pat. No. 2,681,
It can be applied by an extrusion coating method using a hopper described in Japanese Patent No. 294. As required, US Pat. Nos. 2,761,791 and 3,3
508, 947, 2,941, 898, and 3,526, 528, and the method described in Yuji Harasaki, "Coating Engineering", page 253 (published by Asakura Shoten in 1973). It is also possible to divide the coating into two or more layers and simultaneously coat them, and an appropriate method can be selected according to the coating amount, coating speed and the like.

It is necessary to appropriately add a pigment dispersant, a thickener, a flow modifier, a defoaming agent, a foam suppressor, a release agent, and a colorant to the coating liquid used in the present invention, if necessary. It doesn't matter as long as it doesn't hurt.

The multicolor heat-sensitive recording material of the present invention can be used as a multicolor sheet for a printer of a facsimile or an electronic computer which requires high speed recording. In this case, in the case of the present invention in which a diazo compound is used as a color-forming component, it is advantageous to have an exposure zone for photodecomposition, which is advantageous for image storability and multicoloring.

The arrangement of the print head and the exposure zone is roughly classified into two types. First, after printing once, light irradiation for photolysis is performed, and before and after this light irradiation, the recording material feeding mechanism puts the recording material in a print standby state so that it can be printed again at the place where it was once printed. Returning, then printing again, the recording material returns to its original position, so-called 1
It is a head multi-scan method. Another method is a so-called multi-head one-scan method in which recording heads are provided for the number of colors to be recorded and light irradiation zones are provided between them, and both methods may be combined as necessary.
Further, as the light source for photolysis, various light sources that emit light of a desired wavelength can be used, for example, various fluorescent lamps, xenon lamps, xenon flash lamps, mercury lamps of various pressures, photographic flashes, strobes, etc. Various light sources can be used. Further, in order to make the optical fixing zone compact, the light source section and the exposure section may be separated by using an optical fiber.

In the multicolor heat-sensitive recording material of the present invention, each heat-sensitive layer is made to develop a hue of any one of Y (yellow), M (cyan) and C (cyan), so that a full-color image is obtained as a whole. However, the order of C, Y, M or C, M, Y from the support side is preferable from the viewpoint of color reproducibility.

The present invention will be specifically described with reference to the examples, but the present invention is not limited to these examples. Unless otherwise specified, "part" is "part by weight".
Means

[0131]

【Example】

Example 1 Wood pulp comprising 50 parts of LBSP and 50 parts of LBKP was subjected to Canadian Freeness 30 by a disc refiner.
Beating to 0 cc, epoxidized behenic acid amide 0.5 part Anion polyacrylamide 1.0 part Aluminum sulfate 1.0 part Polyamide polyamine epichlorohydrin 0.1 part Cationic polyacrylamide 0.5 part The base paper having a basis weight of 110 g / m ² was made into paper by a rope rope paper machine, and the thickness was adjusted to 97 μm by calendering.

Next, both sides of the base paper were subjected to corona discharge treatment, and then high density polyethylene was coated using a melt extruder to a resin thickness of 50 μm to form a resin layer consisting of a matte surface (this surface Called the face). next,
A low-density polyethylene containing 10% by weight of anatase type titanium dioxide and a trace amount of ultramarine blue was applied to the side opposite to the surface on which the resin layer was formed with a resin thickness of 50 μm.
A resin layer having a glossy surface was formed by coating so as to have a thickness of m (this surface is referred to as a front surface). After the corona discharge treatment on the polyethylene resin coated surface on the back side, aluminum oxide (Alumina sol 100 manufactured by Nissan Chemical Industries) / silicon dioxide (Snow Chicks 0 manufactured by Nissan Chemical Industries) = 1/2 (weight ratio) as water is used as an antistatic agent. And was applied to 0.2 g / m ² by the weight after drying. In this way, a sheet-shaped substrate was produced.

Example 2 A sheet-shaped substrate was prepared in the same manner as in Example 1.

Example 3 A sheet-like substrate was prepared in the same manner as in Example 1 except that the pulp composition was 100 parts LBSP.

Example 4 A sheet-like substrate was prepared in the same manner as in Example 1 except that the basis paper was weighed 140 g / m ² and the thickness was 125 μm.

Example 5 A sheet-like substrate was prepared in the same manner as in Example 1 except that the basis paper was weighed 80 g / m ² and the thickness was 71 μm.

Example 6 50μm thick polyethylene terephthalate film
A multicolor thermosensitive recording layer prepared by melt extrusion biaxial stretching
Was used as the plastic film on the side to be coated. Then LB
Dissolve wood pulp consisting of 50 parts SP50 parts LBKP
Canadian Freeness 300c by refiner
beat to c,               Epoxidized behenic acid amide 0.5 part             Anion polyacrylamide 1.0 part                       Aluminum sulfate 1.0 part Polyamide polyamine epichlorohydrin 0.1 part             Cationic polyacrylamide 0.5 parts Was added at a dry weight ratio of pulp to
80 g / m basis weight depending on machine ²The calender
The thickness was adjusted to 71 μm by the treatment. Then the poly
On one side of the ethylene terephthalate film,
3g / m of polyurethane two-component adhesive²So that
And dry it at 100 ° C for 2 minutes and combine with the above base paper
It thermocompression-bonded at 40 degreeC pressure 20 kg / cm.     Adhesive Polybond AY-651A (manufactured by Sanyo Kasei Co., Ltd.) 100 parts             Polybond AY-651C (manufactured by Sanyo Chemical Industry Co., Ltd.) 15 parts Attach the plastic film of the substrate prepared as above.
Corona discharge treatment was performed on the side of the base paper opposite to the side on which it was attached.
Then, using a melt extruder, the high density polyethylene is
From the matte surface by coating to a thickness of 35 μm
Was formed. Back side polyethylene resin coating
After corona discharge treatment to the surface,
Minium (Alumina sol 100 manufactured by Nissan Chemical Industries) / diacid
Silicon nitride (Snowtex 0 manufactured by Nissan Chemical Industries) = 1/2
(Weight ratio) is 0.2 g / in terms of weight after drying by dispersing in water
m²Applied. In this way, a sheet-like substrate is prepared
It was

Comparative Example 1 A sheet substrate was prepared in the same manner as in Example 1 except that the basis weight of the base paper was 70 g / m ² and the thickness was 60 μm. Comparative Example 2 A sheet-like substrate was prepared in the same manner as in Example 1 except that the basis weight of the base paper was 150 g / m ² and the thickness was 133 μm.

Corona discharge was applied to the supports of Examples 1 to 6 and Comparative Examples 1 to 3 thus obtained, and then the following full-color thermosensitive recording layers were provided. An example of producing a full-color thermosensitive recording material will be shown below. (1) Preparation of cyan thermal recording layer liquid (preparation of capsule liquid containing an electron-donating dye precursor) Solution A 3- (o-methyl-p-dimethylaminophenyl) -3
-(1'-Ethyl-2'-methylindol-3-yl) phthalide (electron donating dye precursor) was added to ethyl acetate 2
After dissolving in 0 part, 20 parts of alkylnaphthalene (high boiling point solvent) was added thereto, and heated to uniformly mix.

A solution A was prepared by adding 20 parts of a 1/3 adduct of xylylene diisocyanate / trimethylolpropane to the resulting solution and stirring the mixture uniformly.

2. Solution B Solution B was prepared by adding 2 parts of a 2% by weight aqueous solution of sodium dodecylsulfonate to 54 parts of a 6% by weight aqueous solution of phthalated gelatin.

Solution A was added to solution B, and the mixture was emulsified and dispersed using a homogenizer to obtain an emulsified dispersion. To the obtained emulsified dispersion liquid, 68 parts of water was added and mixed to homogenize the mixture, which was then heated to 50 ° C. with stirring to encapsulate the microcapsules to an average particle size of 1.2 μm. The reaction was carried out for 3 hours to obtain a capsule liquid.

(Preparation of color developer emulsion dispersion) 1,1- (p
5 parts of -hydroxyphenyl) -2-ethylhexane (developing agent), 0.3 parts of tricresyl phosphate and 0.1 part of diethyl maleate were dissolved in 10 parts of ethyl acetate. The obtained solution was used as a 6% by weight gelatin aqueous solution 50
g and 2 g of a 2 wt% sodium dodecyl sulfonate aqueous solution were added to a mixed solution, and the mixture was emulsified for 10 minutes using a homogenizer to obtain an emulsified dispersion.

(Preparation of coating liquid) The weight ratio of the capsule liquid containing the electron-donating dye precursor / the color developer emulsion dispersion is 1 /
A coating solution was obtained by mixing so as to obtain 4.

(2) Preparation of Magenta Thermosensitive Recording Layer Liquid (Preparation of Capsule Liquid Containing Diazo Compound) 4-N-
2.0 parts of (2- (2,4-di-tert-amylphenoxy) butyryl) piperazinobenzenediazonium hexafluorophosphate (diazo compound: decomposed by light having a wavelength of 365 nm) 2.0 parts were dissolved in 20 parts of ethyl acetate. After that, 20 parts of alkylnaphthalene was further added and heated to uniformly mix. To the resulting solution was added 15 parts of an adduct (capsule wall agent) of xyliresin isocyanate / trimethylolpropane 1/3 and uniformly mixed to obtain a solution of the diazo compound.

The solution of the diazo compound thus obtained was added to a mixed solution of 54 parts of a 6% by weight aqueous solution of phthalated gelatin and 2 parts of a 2% by weight aqueous solution of sodium dodecylsulfonate, and the mixture was emulsified and dispersed using a homogenizer. .

68 parts of water was added to the obtained emulsified dispersion liquid and mixed uniformly, and the mixture was heated to 40 ° C. with stirring to carry out an encapsulation reaction for 3 hours so that the average particle size of the capsules became 1.2 μm. Then, a capsule solution was obtained.

(Preparation of Coupler Emulsion Dispersion) 1- (2 '
-Octylphenyl) -3-methyl-5-pyrazolone (coupler) 2 parts, 1,2,3-triphenylguanidine 2 parts, tricresyl phosphate 0.3 parts and diethyl maleate 0.1 part and ethyl acetate 10. Dissolved in parts. 50 g of a 6% by weight aqueous solution of gelatin was obtained.
And 2 g of 2% by weight sodium dodecyl sulfonate in water
After being added to the mixed aqueous solution, the mixture was emulsified for 10 minutes using a homogenizer to obtain an emulsified dispersion.

(Preparation of coating liquid) A capsule liquid containing a diazo compound / a coupler emulsion was mixed at a weight ratio of 2/3 to obtain a coating liquid.

(3) Preparation of Yellow Thermosensitive Recording Layer Liquid (Preparation of Capsule Liquid Containing Diazo Compound) 2,5-
Dibutoxy-4-tolylthiobenzene diazonium hexafluorophosphate (diazo compound: 420 nm
(Dissolved with light having a wavelength of 3%) was dissolved in 20 parts of ethyl acetate, and then alkylnaphthalene 2
0 part was added and heated to uniformly mix.

To the resulting solution, 1 part of xylylene diisocyanate / trimethylol propane as a capsule wall agent was added.
15 parts of the / 3 adduct were added and mixed uniformly to obtain a solution of the diazo compound.

The solution of the obtained diazo compound was added to a mixed solution of 54 parts of a 6% by weight aqueous solution of phthalated gelatin and 2 parts of an aqueous solution of sodium dodecylsulfonate, and the mixture was emulsified and dispersed using a homogenizer.

68 parts of water was added to the obtained emulsified dispersion, and the homogeneously mixed solution was heated to 40 ° C. with further stirring,
The encapsulation reaction was carried out for 3 hours so that the average particle size of the capsules became 1.3 μm to obtain a capsule solution.

(Preparation of Coupler Emulsion Dispersion) 2-Chloro-5- (3- (2,4-di-tert-pentyl) phenoxypropylamino) acetoacetanilide 2 parts,
1,2,3-Triphenylguanidine 1 part, tricresyl phosphate 0.3 part and diethyl maleate 0.1
Parts in 10 parts ethyl acetate to give 6% by weight of gelatin
50 g of the aqueous solution and 2 g of a 2% by weight aqueous solution of sodium dodecyl sulfonate were added to the mixed solution and emulsified for 10 minutes using a homogenizer to obtain an emulsified dispersion.

(Preparation of Coating Liquid) A capsule liquid containing a diazo compound / a coupler emulsion dispersion was mixed at a weight ratio of 2/3 to obtain a coating liquid.

(4) Preparation of Intermediate Layer Liquid Polyacrylic acid (trade name JULIMER AC-10L: manufactured by Nippon Pure Chemical Co., Ltd.) was added to 10 parts of a 15 wt% aqueous solution of gelatin (# 750: trade name of Nitta Gelatin Co., Ltd.). ) Of 15
3 parts by weight of a wt% aqueous solution was added and mixed uniformly to obtain an intermediate layer liquid.

(5) Preparation of protective layer liquid Itaconic acid-modified polyvinyl alcohol (KL-318:
100 g of 6 wt% aqueous solution of Kuraray Co., Ltd.)
40 wt% zinc stearate dispersion (Hydrin Z: manufactured by Chukyo Yushi Co., Ltd.) was mixed with 10 g of a 30 wt% dispersion of epoxy-modified polyamide (FL-71: trade name of Toho Kagaku Co., Ltd.). (Trade name) 15 g was added to obtain a protective layer liquid.

(6) Preparation of Thermal Recording Material On the polymer layer of each support of Examples 1 to 6 and Comparative Examples 1 to 3, a slide type hopper type bead coating device was used to slide on a slide from the support. Cyan thermal recording layer liquid, intermediate layer liquid, magenta thermal recording layer liquid, intermediate layer liquid,
Multi-layer multilayer coating was performed so as to form a yellow thermosensitive recording layer liquid and a protective layer liquid, and dried to obtain multicolor thermosensitive recording materials.

The coating amount is 6.1 g / m ^{2 for} the cyan heat-sensitive recording layer, 1.0 g / m ^{2 for} the intermediate layer, and 7.8 g / m for the magenta heat-sensitive recording layer in terms of solid content after drying, from the support side. m
² , the intermediate layer was 1.0 g / m ² , the yellow thermosensitive recording layer was 7.2 g / m ^2, and the protective layer was 2.0 g / m ² so that each coating solution was applied.

Using a thermal head KST type (trade name, manufactured by Kyocera Corporation), the applied power and the pulse width were adjusted so that the recording energy per unit area was 34 mJ / mm ^2, and the obtained recording material was obtained. A yellow image was recorded on.

Next, after exposing the yellow thermosensitive recording layer to light by exposing it to an ultraviolet lamp having an emission center wavelength of 420 nm and an output of 40 W for 10 seconds, the applied power and pulse width were adjusted so that the recording energy of the thermal head became 68 mJ / mm ^2. Was adjusted to record a magenta image.

Furthermore, the emission center wavelength is 365 nm and the output is 4
After exposing the magenta thermosensitive recording layer to light for 15 seconds by exposing it to a 0 W ultraviolet lamp, a cyan image was recorded by adjusting the applied power and the pulse width so that the recording energy of the thermal head was 102 mJ / mm ² .

In this way, in addition to the yellow, magenta, and cyan color-developed images, the image portion where the yellow and magenta recordings overlap is red, the image portion where the magenta and cyan recordings overlap is blue, and the yellow The portion where the recordings of cyan and cyan overlap was colored green, and the portion of the image where the recordings of yellow, magenta, and cyan overlap were colored black. Image uniformity was judged by visual inspection, and ○ indicates that the image has no unevenness and is excellent in image uniformity, and ◎ indicates that there is no image unevenness and that the image uniformity is extremely excellent. Further, the mark x indicates that the image unevenness was observed and the image uniformity was poor.

Further, the running property was comprehensively judged by the paper feeding property, the paper discharging property, the stacking property and the like when the thermal recording material was actually printed by the printer. The support stiffness is obtained by measuring the stiffness in the vertical direction and the stiffness in the horizontal direction of the support as the stiffness defined in JIS P8125. The numerical value of () of the support rigidity indicates the rigidity in the printing direction.

[Table 1]

From Table 1, the rigidity in the printing direction is 1.5 to 8.
When 0 gf / cm, the image quality uniformity and the running property are excellent, and particularly when 3.0 g to 6.0 gf / cm, the image quality uniformity and the running property are more excellent.

[0166]

As described above, according to the present invention, the uniformity of an image can be improved and the running property can be improved by adjusting the rigidity of the sheet-like substrate used for the multicolor thermosensitive recording material within a specific range. Can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining rigidity in the present invention.

FIG. 2 is a sectional view showing an embodiment of the multicolor heat-sensitive recording material of the present invention.

[Explanation of symbols]

11 Strip-shaped substrate 12 Recording paper 21 Support 22 Transparent cyan coloring layer 23 Middle class 24 Transparent yellow coloring layer 25 Middle class 26 Transparent magenta coloring layer 27 Transparent protective layer

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-6-336079 (JP, A) JP-A-61-279589 (JP, A) JP-A-3-91740 (JP, A) JP-A-6- 278360 (JP, A) JP 7-164743 (JP, A) JP 6-286309 (JP, A) JP 62-23778 (JP, A) JP 62-268684 (JP, A) JP-A-7-92611 (JP, A) JP-A-6-230517 (JP, A) JP-A-8-187938 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) D21H 11/00-27/42 B41M 5/18

Claims (5)

(57) [Claims] 1. A heat-sensitive recording method using a multicolor heat-sensitive recording material comprising two or more heat-sensitive recording layers provided on a support, wherein the support is a sheet-like substrate having resin layers on both sides of a raw paper. A heat-sensitive recording method using a multicolor heat-sensitive recording material, characterized in that a direction in which the rigidity of the sheet-shaped substrate defined by JIS P8125 is 1.5 to 8.0 gf · cm is set as a printing direction. 2. The sheet-shaped substrate according to JIS P8125.
The heat-sensitive recording method using the multicolor heat-sensitive recording material according to claim 1, wherein the printing direction is a direction having a rigidity of 3.0 to 6.0 gf · cm defined in 1. 3. A heat-sensitive recording method using a multicolor heat-sensitive recording material according to claim 1, wherein the resin layer is formed by melt extrusion coating. 4. A heat-sensitive recording method using a multicolor heat-sensitive recording material according to claim 1, wherein the resin layer is formed by dry lamination. 5. The heat-sensitive recording method using a multicolor heat-sensitive recording material according to claim 1, wherein the resin layer is made of an olefin resin.