JP2003266950A - Dye dispersion and thermal recording material using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal recording material which is excellent in productivity and free of liquid covering and in-liquid agglomeration and can be made into particulates and which has high coloring sensitivity and a high degree of whiteness of the ground and is excellent in the shelf stability of a colored image and the ground, in a method of dispersion using a medium. <P>SOLUTION: In a dispersion of leuco dye, the leuco dye is dispersed with an anionic surfactant contained as a dispersant. The average particle diameter of the leuco dye is 0.10-0.30 μm. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more specifically, it has high coloring sensitivity and high whiteness of the background.
The present invention also relates to a heat-sensitive recording material excellent in storage stability of a color image and background.

[0002]

2. Description of the Related Art In recent years, with the diversification of information and the expansion of needs, various recording materials have been researched, developed and put into practical use in the information recording field.
Since (1) simple image recording can be performed only by a heating process, (2) necessary mechanism is simple, downsizing is easy, and recording material is easy to handle and inexpensive. Information processing field (desktop computer, computer output, etc.), medical measurement recorder field, low / high speed facsimile field, automatic ticket vending machine field (tickets, entrance tickets, etc.), thermal copying machine field, P0S system label field, etc. Widely used. As these heat-sensitive recording materials, materials which rapidly develop a high density color and have high fastness to the colored image and the background are demanded.

Among them, as a means for rapidly developing a high density of color (= higher sensitivity), a material which is eutectic with a leuco dye or a color developer as a low melting point developer or a sensitizer to cause a melting point drop. However, basically, lowering the melting point of the color developer and sensitizer is highly effective for increasing the sensitivity, but since the color development temperature decreases, the sensitivity is improved and the background fog is low at low temperatures. It has the drawback of occurring. Further, in recent years, a developer having a high molecular weight has been developed as a developer for improving chemical resistance (WO99 / 51444, WO00).
/ 14058, JP-A-8-333329, etc.). However, because of the high molecular weight of these developers,
Even if the sensitivity is increased by using a sensitizer, the sensitivity and color density are still insufficient, and further improvement in sensitivity is desired.

On the other hand, as another means for increasing the sensitivity, various proposals have heretofore been made to make the leuco dye into fine particles to make the heat-sensitive recording material highly sensitive. For example, use of a leuco dye having a volume average particle diameter of 2 μm or less (Japanese Patent Laid-Open No. Sho 5
7-47693), two or more types of leuco dyes, which are pulverized at the same time so that the volume average particle diameter is 2 μm or less, are used (described in JP-A-7-223375). A heat-sensitive recording material (described in JP-A-7-186527) containing a leuco dye having a particle diameter of 0.1 to 0.8 μm, a coloring agent, and colloidal silica has been proposed.

These fine particles of leuco dyes are prepared by dispersing a water-soluble polymer such as a cellulose-based polymer material or polyvinyl alcohol as a dispersant in a water disperser such as a ball mill, a sand mill, a high speed jet mill or an attritor. It is a method of dispersing until a predetermined particle size is achieved, but it requires labor, time, machinery, etc. to make it into fine particles, which results in high cost, and 0.3 μm using a water-soluble polymer.
When the particle size is less than m, the surface of the dye is activated and secondary agglomeration of the dispersoid in the liquid easily occurs, resulting in poor liquid stability. Also, the surface of the leuco dye is activated and dispersed for a long time. As a result, fog of the dye dispersion liquid is generated, and when it is used as a heat-sensitive recording material, the whiteness of the background is lowered, and the like.

Further, in order to solve the above-mentioned problem of mechanical dispersion, a method has been proposed in which a leuco dye is made into fine particles by an emulsification method. For example, JP-A-61-218
No. 7,283 discloses that a solution of a leuco dye in an organic solvent is emulsified in water, but a step of removing the organic solvent after emulsification is required, and a background fog is generated due to the residual organic solvent. There are drawbacks such as. Further, JP-A-56-164890 discloses that a leuco dye is emulsified with a heat-fusible substance, but the heat-fusible substance lowers the melting point and heat-resistant storage stability. Further, Japanese Patent Application Laid-Open No. 7-186531 describes a heat-sensitive recording material in which the volume average particle diameter of the leuco dye is 0.3 μm or less and contains an ultraviolet absorber. , A dye is heat-melted and emulsified with a high-pressure homogenizer using a silicon-based emulsifier. In addition, JP-A-7-22337
No. 9 discloses that the volume average particle diameter of the leuco dye is 1.0 μm.
What is emulsified and dispersed is described below, and here, it is described that what is obtained by heating and melting a leuco dye is emulsified and dispersed by high pressure spraying from a high speed stirrer or a nozzle using an emulsifier. The melting point of leuco dye is usually 150.
C. or higher, and a special device such as a high-pressure container is required to heat-melt the leuco dye and emulsify it in water as described in JP-A-7-186531 and JP-A-7-223379. Therefore, it is industrially difficult to mass-produce.

With respect to the support of the thermal paper, synthetic paper, film, plastic, etc. are known in addition to general high-quality paper, but recently, from the viewpoint of resource conservation, recovered paper is used and used as a raw material. Is required to do. JP-A-58-25986 and JP-A-2000-272248
The publication discloses a heat-sensitive recording paper in which a heat-sensitive recording layer is coated on a paperboard containing waste paper pulp. However, when a support containing waste paper pulp is used as the thermal recording paper, there arises a problem that the storage stability is lowered (especially, the image is deteriorated under high temperature and high humidity).

[0008]

DISCLOSURE OF THE INVENTION The object of the present invention is to improve the above-mentioned drawbacks of the prior art, and in the dispersion method using a medium, the productivity is good, and it is possible to form fine particles without liquid fog or aggregation in the liquid. It is an object of the present invention to provide a heat-sensitive recording material having high color development sensitivity and high whiteness of the background when used as a thermal paper, and excellent in storage stability of a color image and background.

[0009]

Means for Solving the Problems The present invention was conducted in the mechanical dispersion method, and as a result of studying fine particle formation of a leuco dye having good productivity and free from liquid fog and liquid aggregation,
By using an anionic surfactant as the dispersant, it is possible to improve the dispersion stability of the leuco dye pulverized into fine particles, improve secondary aggregation and liquid fog, and shorten the dispersion time (improve dispersion efficiency). The volume average particle size is 0.1
It has been found that there is provided a leuco dye dispersion characterized in that it is ˜0.3 μm. Further, it has a polyoxyethylene group as an anionic surfactant, the number of moles of polyoxyethylene in the surfactant having a polyoxyethylene group is 15 or less, and 0.07 μm or less in the leuco dye dispersion liquid. Particle size component content is 1%
The following content, 5 to 25% by weight of a surfactant with respect to the leuco dye, and 1 to 10% by weight of a silicone emulsion with respect to the leuco dye. On the other hand, by providing a leuco dye dispersion liquid containing a polymer dispersant, wherein the polymer dispersant is partially saponified polyvinyl alcohol or polyvinyl alcohol acrylic sulfonic acid metal salt Has been found to be resolved.

When the water-soluble polymer which has been used as a dispersant has been made into fine particles of 0.3 μm or less, the water-soluble polymer cannot cover the surface of the fine particles, which is increased due to the formation of fine particles, so that electrical stability is improved. It is known to lose and cause secondary aggregation. Further, when polyvinyl alcohol or the like is usually used as a dispersant to disperse the leuco dye into fine particles, the smaller the particle size, the higher the coloring density of the dispersion. Further, when it is mixed with a color developer, the coloring becomes more violent, and when it is used as a thermal recording paper, the background density becomes higher. As a cause for this, the unsaponifiable portion of polyvinyl alcohol changes due to high shearing due to atomization, and the pH of the dispersion decreases due to the formation of acetic acid, causing a partial color development, and a part of the dye particles being amorphous. It is presumed that the color will be easily changed and color will be easily generated. In addition, in the dispersion method using the medium until reaching the fine particles of up to 0.3 μm, it is difficult to put into practical use because the dispersion time requires a long time.

In the present invention, it was discovered that the use of the above-mentioned surfactant as a dispersant can solve various drawbacks occurring in a water-soluble polymer compound, and the stability of dye fine particles can be improved. Secondary aggregation and liquid fog were improved, and dispersion time was shortened (improvement of dispersion efficiency).

There are various compounds as anionic surfactants, such as fatty acid metal soaps, polycarboxylic acid type polymer activators, higher alcohol sulfate ester salts, alkyl polyether sulfate ester salts and higher alcohols. Ethylene oxide adducts, alkylaryl sulfonates, alkyl sulfonic acids, aryl sulfonic acids, phosphoric acid esters, aliphatic phosphoric acid esters, aromatic phosphoric acid esters, polyoxyethylene alkyl sulfuric acid esters, polyoxy Ethylene aryl sulfates, polyoxyethylene alkyl aryl sulfates, dialkyl sulfosuccinates, alkylbenzene sulfonates, polyoxyalkylene alkyl ether phosphates, polyoxyalkylene aryl ethers Esters, polyoxyalkylene alkylaryl ether phosphate esters, and the like, anionic surfactants in particular having a polyoxyethylene group Among these are preferred from the viewpoint of dispersion stability. Specifically, for example, sodium polyoxyethylene lauryl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, triethanolamine polyoxyethylene lauryl ether sulfate, ammonium polyoxyethylene lauryl ether sulfate, Polyoxyethylene sodium lauryl sulfosuccinate, sodium polyoxyethylene xylyl phenyl ether sulfate, sodium polyoxyethylene styryl phenyl ether sulfate, ammonium polyoxyethylene styryl phenyl ether sulfate, triethanolamine polyoxyethylene xylyl phenyl ether sulfate, polyoxyethylene Examples include styryl phenyl ether sulfate triethanolamine. These anionic surfactants may be a mixture of two or more.

The surfactant having a polyoxyethylene group used in the present invention has an addition mole number of ethylene oxide (EO) of 60 or less, preferably 20 or less, particularly preferably 15 or less. In the surfactant having a group, a terminal ether residue is preferably a saturated or unsaturated aliphatic hydrocarbon group, an aryl group, or an aryl group substituted with a saturated or unsaturated aliphatic hydrocarbon group, and these aryl groups are preferable. As a basis,
Examples thereof include a phenyl group, a naphthyl group, a biphenyl group, a binaphthyl group, a terphenyl group, and a quaterphenyl group. More preferable substituents include saturated or unsaturated aliphatic hydrocarbon groups having 8 to 20 carbon atoms such as octyl group, nonyl group, lauryl group, tridecyl group, cetyl group, stearyl group, and oleyl group, and , Octylphenyl group, nonylphenyl group, laurylphenyl group, tridecylphenyl group, cetyl group, phenyl, stearylphenyl group, oleylphenyl group, etc. substituted with a saturated or unsaturated aliphatic hydrocarbon group having 8 to 20 carbon atoms. An aryl group, and further, a ring assembly hydrocarbon group of an aromatic ring which may be substituted with an alkyl group or an alkenyl group such as a phenylxylyl group, a styrylphenyl group, a biskisilylphenyl group and a trixylylphenyl group. Can be mentioned. Further, the content of the particle size component of 0.07 μm or less in the leuco dye dispersion is 1% or less, and the anionic surfactant is contained in an amount of 5 to 25% by weight based on the leuco dye. It is preferable to add 1 to 10% by weight of silicon emulsion to the dye. By using the leuco dye dispersion thus prepared, a thermal recording material having high sensitivity, high heat resistance and excellent background whiteness can be provided. In particular, regarding the background whiteness, it was found that the surfactant having a polyoxyethylene group as a dispersant for the leuco dye varies depending on the number of moles of polyoxyethylene, and the smaller the number of moles, the more the background whiteness of the thermal recording material. Tends to improve. Above all, the effect is recognized when the number of moles is 20 or less, and particularly when the number of moles is 1
It becomes remarkable when it is 5 or less.

The amount of the anionic surfactant used is
If the amount used is less than 5%, the particle size does not decrease, and
There are problems such as secondary aggregation of particles, and 25%
When it is used in excess of the above range, when it is used as a thermosensitive recording medium, color development may be impeded, resulting in problems such as a decrease in color density and a decrease in storage stability.

On the other hand, with respect to the volume average particle size of the leuco dye, the smaller the particle size, the higher the sensitivity, but the particle size is less than 0.
When the thickness is 1 μm or less, heat-resistant surface fog occurs in heat-resistant storage stability, causing a problem in practical use. Therefore, 0.1
It is desirable to control the volume average particle diameter in the range of 0.3 μm to achieve both heat resistant storage stability and high sensitivity. Furthermore,
When the ratio of the particle size is 0.07 μm or less, the background fog occurs as in the case of the volume average particle size, and the ratio is 1
Since it becomes remarkable when it exceeds%, a ratio of 1% or less is particularly preferable.

Particularly preferred surfactants having a polyoxyethylene group used in the present invention include, but are not necessarily limited to, the compounds represented by the following general formula (III).

[0017]

X-O- (CH2CH2O) n-SO3-Y (III) (In the formula, X is a saturated or unsaturated aliphatic hydrocarbon group, an unsubstituted or saturated or unsaturated aliphatic hydrocarbon group, Alternatively, it represents an aryl group substituted with an unsubstituted or saturated unsaturated aliphatic hydrocarbon group, and Y is Na, NH4, N
(CH2CH2OH) 3 and the like, and n represents an integer of 60 or less. Here, n is 20 or less as a preferable number,
More preferable number is 15 or less. X may represent two or more kinds of substituents,
For example, when X is an alkyl group having 12 and 13 carbon atoms, it means a mixture of compounds having these alkyl groups. ) Specific examples of the substituent X include a saturated or unsaturated aliphatic hydrocarbon group having 8 carbon atoms such as octyl group, nonyl group, lauryl group, tridecyl group, cetyl group, stearyl group and oleyl group. To 20 saturated or unsaturated aliphatic hydrocarbon groups, on the other hand, in the aryl group substituted with an unsubstituted or saturated unsaturated aliphatic hydrocarbon group, the unsubstituted aryl group is a phenyl group, Examples thereof include naphthyl group, biphenyl group, binaphthyl group, terphenyl group, and quaterphenyl group. Further, in the above aryl group, the aryl group substituted with a saturated or unsaturated aliphatic hydrocarbon group includes an octylphenyl group, a nonylphenyl group, a laurylphenyl group, a tridecylphenyl group, a cetyl group phenyl, and a stearylphenyl group. , An aryl group substituted with a saturated or unsaturated aliphatic hydrocarbon group having 8 to 20 carbon atoms such as an oleylphenyl group, and further, a xylylphenyl group, a biskisilylphenyl group, a trixylylphenyl group, A ring assembly hydrocarbon group substituted with an alkyl or alkenyl group such as a styrylphenyl group is also included as a preferable substituent in the aryl group substituted with a saturated or unsaturated aliphatic hydrocarbon group.

Examples of the polymer dispersant used together with the anionic surfactant in the present invention include polyvinyl alcohol, modified polyvinyl alcohol starch and its derivatives, and cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose and ethyl cellulose. Among them, polyvinyl alcohol acrylic sulfonic acid metal salt is preferable. Further, the amount of the polymer dispersant used is 2 to 1 part of the leuco dye.
It is preferable to use 10%. If the amount used is less than 2%, the image water resistance improving effect is not recognized. If it is used in excess of 10%, secondary aggregation may occur.

The volume average particle size of the leuco dye is from 0.10 to 0.
Obtaining a 30 μm dye dispersion by a dispersion method using a medium prolongs the dispersion time, and
At present, industrial production is not possible because it is difficult to set conditions that prevent secondary aggregation. By changing the dispersant from a water-soluble polymer to an anionic surfactant, the dispersion efficiency has been considerably improved, but it is still insufficient for industrial production.

Therefore, in the present invention, as a method of further improving the dispersion efficiency, the diameter of the medium used is 0.8 mm to 0.
By making it 3 mm, the dispersion efficiency is improved. When the diameter of the medium used exceeds 0.8 mm, it takes a long time to reach the particle size of the leuco dye to 0.3 μm or less. This is because particles crushed to around 1 μm reduce the probability of collision between media and particles.
When dispersed to 1 μm or less, the dispersion efficiency is lowered and it takes a long time to make the particles fine. Further, when the diameter of the used medium is less than 0.3 mm, it is difficult to separate the medium and the dye dispersion liquid, and the productivity is lowered and the separation is insufficient. Become. Therefore, from the viewpoint of efficiency and productivity of atomization, the media diameter is 0.8
It is preferable to set it to mm to 0.3 mm.

As described above, in consideration of dispersion efficiency, it is preferable to select the media diameter according to the particle diameter, and for particles of 1 μm or more, the diameter of the used media is 0.8.
It is best to select mm to 1 mm for dispersion efficiency.
For particles of less than μm, the diameter of the media used is 0.8 mm
Since 0.3 mm is the best for dispersion efficiency,
0.8mm diameter is the best way to improve dispersion efficiency
Coarsely crushed using ~ 1.0 mm media, then 0.
It is preferable to carry out two-stage dispersion in which dispersion is performed using a medium of 5 mm to 0.3 mm. Although glass is generally used as the material of the medium, considering the dispersion efficiency, a medium such as zirconia having a large specific gravity is used to increase the energy at the time of collision between the particles and the medium,
It is preferable to carry out the pulverization efficiently. Examples of glass media include soda glass (manufactured by AIMEX Co., Ltd.) and HiBeads (manufactured by Ashizawa Co., Ltd.), and examples of zirconia include Nikkato zirconia beads and Toray Co. zirconia beads. Further, bubbles in the liquid at the time of dispersion enter between the particles and the medium, which hinders the collision of the particles with the medium and reduces the dispersion efficiency. Therefore, the removal of bubbles in the liquid improves the dispersion efficiency. .

Therefore, silicone emulsion, mineral oil, higher alcohol, acetylene glycol, higher fatty acid, etc. can be used as the defoaming agent. In particular, silicone emulsion has a high antifoaming effect, and its addition amount is
If it is less than 1% with respect to the leuco dye, and if it exceeds 10%, there is a problem that when it is used as a thermosensitive recording material, color development is inhibited, resulting in a decrease in color density and a decrease in storage stability. By using it in the range of 10%, bubbles in the liquid can be removed, and the dispersion efficiency can be improved.

As the dispersing machine using media, a ball mill, an attritor, a sand mill, an SC mill, a ring mill, a spike mill, a co-ball mill, a dyno mill or the like can be used. Among them, the SC mill, the ring mill and the spike mill have a strong centrifugal force. It is suitable for shortening the dispersion time (improving the dispersion efficiency) because it has a mechanism for adding a force and can increase the shearing force applied to the pulverized material.

In the present invention, when the support made of waste paper pulp is used, the reason why the storage stability is deteriorated has not been clarified yet, but the waste paper pulp contains a surfactant. It is presumed that the storage stability is lowered because the color development of the color developer and the dye is inhibited by. In the present invention, by decreasing the particle size of the dye, the contact probability between the color developer and the dye is increased, and since it is difficult for the surfactant to inhibit color development, when a support made of waste paper pulp is used. However, it is considered that good storage stability can be obtained.

The leuco dyes used in the thermosensitive coloring layer of the present invention may be used alone or as a mixture of two or more kinds.
As such leuco dyes, those applied to this type of heat-sensitive material are arbitrarily applied, for example, triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, indolinophtalide-based, etc. Leuco compounds of dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis ( p-dimethylaminophenyl) -6-diethylaminophthalide,
3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino-5,7 -Dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-
Diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-
(Np-tolyl-N-ethylamino) -6-methyl-
7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3. 6-bis (diethylamino)-
9- (o-chloroanilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-di- n-Butylamino-7- (o-chloroanilino) fluorane, 3-N-methyl-N, n-amylamino-6-
Methyl-7-anilinofluorane, 3-N-methyl-N
-Cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) -5
-Methyl-7- (N, N-dibenzylamino) fluorane,

Benzoyl leuco methylene blue, 6'-
Chloro-8'-methoxy-benzoindolino-spiropyran, 6'-bromo-3'-methoxy-benzoindolino-spiropyran, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2 '-Methoxy-5'-chlorophenyl) phthalide, 3- (2'-hydroxy-4'-
Dimethylaminophenyl) -3- (2'-methoxy-5 '
-Nitrophenyl) phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl) phthalide, 3- (2'-methoxy-4'-dimethylamino) Phenyl) -3- (2'-hydroxy-4'-chloro-5'-methylphenyl) phthalide, 3- (N-ethyl-N-tetrahydrofurfuryl)
Amino-6-methyl-7-anilinofluorane, 3-N
-Ethyl-N- (2-ethoxypropyl) amino-6-
Methyl-7-anilinofluorane, 3-N-methyl-N
-Isobutyl-6-methyl-7-anilinofluorane,
3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoro) Methylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-
Diethylamino-5-chloro-7- (α-phenylethylamino) fluorane, 3- (N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxy Carbonylphenylamino) fluorane, 3-diethylamino-
5-methyl-7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane,

2-chloro-3- (N-methyltoluidino) -7- (pn-butylanilino) fluorane, 3
-Di-n-butylamino-6-methyl-7-anilinofluorane, 3,6-bis (dimethylamino) fluorenspyrro (9,3 ')-6'-dimethylaminophthalide, 3
-(N-benzyl-N-cyclohexylamino) -5,
6-benzo-7-α-naphthylamino-4′-bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-diethylamino-6-methyl-7
-Mesitidino-4 ', 5'-benzofluorane, 3-N-
Methyl-N-isopropyl-6-methyl-7-anilinofluorane, 3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane, 3-diethylamino-
6-methyl-7- (2 ', 4'-dimethylanilino) fluorane, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-
7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-
7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro- (α-phenylethylamino) fluorane,

3- (N-ethyl-p-toluidino) -7
-(Α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-
7- (α-phenylethylamino) fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3- (N-methyltoluidino) -7- (p-N-butylanilino) fluorane,

3,6-bis (dimethylamino) fluorene spiro (9,3 ')-6'-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino)
-5,6-benzo-7-α-naphthylamino-4'-bromofluorane, 3-diethylamino-6-chloro-7
-Anilinofluorane, 3-N-ethyl-N-(-2-
Ethoxypropyl) amino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane, 3
-Diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluorane,

3-p-dimethylaminophenyl) -3-
{1,1-bis (p-dimethylaminophenyl) ethylene-2-yl} phthalide, 3- (p-dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) ethylene-2- Il} -6-dimethylaminophthalide, 3- (p-dimethylaminophenyl) -3-
(1-p-Dimethylaminophenyl-1-phenylethylene-2-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-
1-p-chlorophenylethylene-2-yl) -6-dimethylaminophthalide, 3- (4'-dimethylamino-
2'-methoxy) -3- (1 "-p-dimethylaminophenyl-1" -p-chlorophenyl-1 ", 3" -butadiene-4 "-yl) benzophthalide, 3- (4'-dimethylamino-2) '-Benzyloxy) -3- (1 "-
p-dimethylaminophenyl-1 "-phenyl-1",
3 "-butadiene 4" -yl) benzophthalide, 3-dimethylamino-6-dimethylamino-fluorene-9-
Spiro-3 '-(6'-dimethylamino) phthalide,
3,3-bis {2- (p-dimethylaminophenyl)-
2-p-methoxyphenyl) ethenyl} -4,5,6
7-Tetrachlorophthalide, 3-bis {1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl}-
5,6-dichloro-4,7-dibromophthalide, bis (p-dimethylaminostyryl) -1-naphthalenesulfonylmethane, bis (p-dimethylaminostyryl)-
1-p-tolylsulfonylmethane and the like.

Specific examples of the color developing agent used in the present invention include those shown below. 4,
4'-isopropylidene bisphenol, 4,4'-isopropylidene bis (o-methylphenol), 4,
4'-secondary butylidene bisphenol, 4,
4'-isopropylidene bis (2-tert-butylphenol), 4,4'-methylenebis (oxyethylenethio) diphenol, zinc p-nitrobenzoate, 1,
3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid,
2,2- (3,4′-dihydroxydiphenyl) propane, bis (4-hydroxy-3-methylphenyl) sulfide, 4- {β- (p-methoxyphenoxy) ethoxy} salicylic acid, 1,7-bis (4 -Hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (4-hydroxyphenylthio) -5-oxapentane,

Phthalic acid monobenzyl ester monocalcium salt, 4,4'-cyclohexylidene diphenol,
4,4'-isopropylidene bis (2-chlorophenol), 2,2'-methylene bis (4-methyl-6-tert-butylphenol), 4,4'-butylidene bis (6-tert-butyl-2-methyl) Phenol, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,
3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4'-thiobis (6-
Tert-butyl-2-methyl) phenol, 4,
4'-diphenol sulfone, 4-isopropoxy-
4'-hydroxydiphenyl sulfone, 4-benzyloxy-4'-hydroxydiphenyl sulfone, 4,4'-
Diphenol sulfoxide, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, benzyl protocatechuate,

Stearyl gallate, lauryl gallate,
Octyl gallate, 1,3-bis (4-hydroxyphenylthio) -propane, N, N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, salicylanilide, bis- (4- Hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl)
Acetic acid benzyl ester, 1,3-bis (4-hydroxycumyl) benzene, 1,4-bis (4-hydroxycumyl) benzene, 2,4′-diphenol sulfone, 2,
2'-diallyl-4,4'-diphenol sulfone, 3,
4-dihydroxyphenyl-4'-methyldiphenyl sulfone, zinc 1-acetyloxy-2-naphthoate, 2
-Zinc acetyloxy-1-naphthoate, zinc 2-acetyloxy-3-naphthoate, α, α-bis (4-hydroxyphenyl) -α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, Tetrabromobisphenol S, 4,4'-thiobis (2-methylphenol), 4,4'-thiobis (2
-Chlorophenol), (poly) 4-hydroxybenzoic acid derivative (described in WO99 / 51444), urea urethane compound (described in WO00 / 14058), diphenylsulfone derivative, sulfonylaminocarbonylamide group (A color developer described in JP-A-08-333329), a polycondensation of a trivalent or higher polyvalent isocyanate compound represented by the following formula (I) and an aromatic amine represented by the formula (II) An oligomer composition obtained by the reaction,

[0035]

Embedded image X (NCO) a (I)

[0036]

[Chemical 6] (In the formula, X represents a group having a valence of 3 or more, and a represents an integer of 3 or more.
Further, b and c are integers of 0 to 5 and are combinations satisfying the relation that b + c is an integer of 1 to 5. Z represents a hydrogen atom, an alkyl group, an alkenyl group or an aryl group, and in the case of an aryl group, it also includes the case where a condensed ring structure is formed. d is an integer of 0 to 4, such as b + c + d = 1 to 5 (provided that b + c = 1 to 5 is an integer), and the like.

Here, the oligomer composition used as the color developer has an isocyanate group (NC) as the trivalent or more polyvalent isocyanate represented by the general formula (I).
Those having 3 or more O groups) in the molecule may be used alone or in combination. X in the general formula (I)
Is a trivalent or higher valent group, and the structure thereof is not particularly limited, but examples thereof include the following structures. Examples of X include (a) 3 derived from a carbonyl group, a sulfonyl group, an aliphatic hydrocarbon, and an aromatic hydrocarbon.
A group having a valence of 3 or more, and (b) a valence of 3 or more derived from an aliphatic hydrocarbon containing at least one hetero atom, a carbonyl group, a sulfonyl group, an ester group, an amide group, a urethane group or an aromatic ring in the main chain. Group (c) one or more heteroatoms, a carbonyl group, a sulfonyl group, an ester group, an amide group, a urethane group, an alkylene, three or more linked by an aliphatic hydrocarbon containing a heteroatom in the main chain And trivalent or higher valent groups derived from the aromatic hydrocarbons. Further, although included in the above description, examples of X include those having the structures represented by the following general formulas (III) and (IV).

[0038]

[Chemical 7]

[0039]

[Chemical 8] In the formula, Y represents a divalent group, and X in the formula is (d) a carbonyl group, a sulfonyl group, a divalent group derived from an aliphatic hydrocarbon or an aromatic hydrocarbon, and (e) in the main chain. One or more heteroatoms, a carbonyl group, a sulfonyl group, an ester group, an amide group, a urethane group, a divalent group derived from an aliphatic hydrocarbon containing an aromatic ring, (f) one or more heteroatoms,
Carbonyl group, sulfonyl group, ester group, amide group,
A divalent group derived from a urethane group, alkylene, and two aromatic hydrocarbons linked by an aliphatic hydrocarbon containing a hetero atom in the main chain is shown. Various types of trivalent or higher polyvalent isocyanates represented by the general formula (I) containing X can be used. These trivalent or higher polyvalent isocyanate compounds can be generally derived from various diisocyanate compounds. Examples of the diisocyanate compound used here include tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, polymethylene polyphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 1,5-
Naphthalene diisocyanate, various (o, m, p) xylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, various (o, m, p) phenylene diisocyanate, 1,4-cyclohexyl Various compounds including diisocyanate, lysine diisocyanate, 3,3-dimethylbiphenyl-4,4′-diisocyanate, dianisidine diisocyanate and various (m, p) tetramethylxylene diisocyanate can be mentioned. Reaction with a polyhydric alcohol having a valence of 3 or more such as trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, or diisocyanate Trimmer structured or may be made three or more valences isocyanate compound of various structures by biuret structured.

The following are trivalent polyisocyanate derivatives derived from 1,6-hexamethylene diisocyanate, tolylene diisocyanate, xylene diisocyanate, 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate and 1,4-cyclohexyl diisocyanate. Is illustrated.

[0041]

[Chemical Formula 9] I-1 (Coronate H made by Nippon Polyurethane)
L)

[0042]

[Chemical Formula 10] I-2 (Coronate L made by Nippon Polyurethane)

[0043]

[Chemical Formula 11] I-3 (Takenate D110 manufactured by Takeda Pharmaceutical Co., Ltd.
N)

[0044]

[Image Omitted] I-4 (Coronate 20 made by Nippon Polyurethane)
67)

[0045]

[Chemical Formula 13] I-5 (Takenate D120 manufactured by Takeda Pharmaceutical Co., Ltd.
N)

[0046]

[Chemical Formula 14] I-6 (Takenate D140 manufactured by Takeda Pharmaceutical Co., Ltd.
N)

[0047]

[Chemical Formula 15] I-7 (Nippon Polyurethane Coronate H
X)

[0048]

[Image Omitted] I-8 (Coronate 20 made by Nippon Polyurethane
30)

[0049]

[Chemical Formula 17] I-9 (Sumika Bayer Urethane Death Module Z-4470)

[0050]

[Chemical formula 18] I-10 (Sumijour N3200 made by Sumika Bayer Urethane Co., Ltd.)

On the other hand, the following are specific examples of the aromatic amine derivative of the general formula (II) which constitutes the oligomer composition. 4-aminophenol, 3-aminophenol, 2-aminophenol, 2-amino-3-methylphenol, 2-amino-4-methylphenol, 2
-Amino-5-methylphenol, 4-amino-2-methylphenol, 3-amino-2-methylphenol,
4-amino-3-methylphenol 5-amino-2-methoxyphenol, 2-amino-4-t-butylphenol, 2-amino-4-chlorophenol, 6-amino-2,4-dimethylphenol, 4-amino -2,6-
Dichlorophenol, 4-amino-2,5-dimethylphenol, 4-amino-2,6-dibromophenol,
4-amino-2,3-dimethylphenol, 5-amino-1-naphthol, 1-amino-2-naphthol, 4-
Aminophenol derivatives such as amino-1-naphthol and 3-amino-2-naphthol. 4-aminobenzoic acid,
3-aminobenzoic acid, 2-aminobenzoic acid (anthranilic acid), 2-amino-3-methylbenzoic acid, 2-amino-6-methylbenzoic acid, 2-amino-5-methylbenzoic acid, 2-amino- 3-methoxybenzoic acid, 3-amino-
4-methoxybenzoic acid, 2-amino-5-chlorobenzoic acid, 3-amino-2-methylbenzoic acid, 3-amino-4
-Methylbenzoic acid, 4-amino-3-methylbenzoic acid,
2-amino-3-chlorobenzoic acid, 2-amino-4-chlorobenzoic acid, 3-amino-4-chlorobenzoic acid, 4-
Amino-2-chlorobenzoic acid, 5-amino-2-chlorobenzoic acid, 2-amino-5-bromobenzoic acid, 2-amino-5-iodobenzoic acid, 2-amino-4-fluorobenzoic acid, 2- Amino-5-fluorobenzoic acid, 4-nitroanthranilic acid, 5-nitroanthranilic acid, 2-
Aminoterephthalic acid, 5-aminoisophthalic acid, 3,5
-Dimethyl anthranilic acid, 3,5-dibutyl anthranilic acid, 4-amino-3,5-diaiodobenzoic acid,
3,5-diaiodoanthranilic acid, 4-amino-5-
Chloro-2-methoxybenzoic acid, 2-amino-4,5-
Benzoic acid derivatives such as dimethoxybenzoic acid and 3-amino-2-naphthoic acid. Salicylic acid derivatives such as 4-aminosalicylic acid, 5-aminosalicylic acid, 3-aminosalicylic acid, 5-hydroxyanthranilic acid, and 3-amino-4-hydroxybenzoic acid, and hydroxybenzoic acid derivatives.

The developer is 2-1 to 1 part of the leuco dye.
Used 0 parts. In order to produce a thermal paper having improved chemical resistance, a (poly) 4-hydroxybenzoic acid derivative,
Urea urethane compound, diphenyl sulfone derivative,
4,4'-dihydroxydiphenyl sulfone, a developer having a sulfonylaminocarbonylamide group, and an oligomer composition obtained by a polycondensation reaction of a polyvalent isocyanate compound and an aromatic amine are preferable, and any of these developers is preferable. A dye having a normal particle size has a low sensitivity and is insufficient in practical use, but when combined with a finely divided dye, the sensitivity can be improved, and the sensitivity can be improved to a level at which it can be actually used. It is also possible to use a nonionic surfactant and a water-soluble polymer together with the above-mentioned anionic surfactant in order to make the leuco dye fine particles, improve the dispersion efficiency, and stabilize the liquid.

Examples of the nonionic surfactant and water-soluble polymer used in the present invention include the following.
Polyoxyethylene octyl phenyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene tridecyl ether, polyoxyethylene castor oil ether, polyoxyethylene cetyl ether, polyoxyethylene Stearyl ether, polyoxyalkylene alkyl ether,
Polyoxyethylene oleate, polyoxyethylene nonyl phenyl ether, sorbitan laurylate, sorbitan stearate, sorbitan oleate, sorbitan trioleate, polyoxyethylene sorbitan laurate, polyoxyethylene sorbitan stearate,
Polyoxyethylene sorbitan oleate, polyoxyethylene sorbitan trioleate, polyoxyethylene polystyrene phenyl ether, polyethylene glycol, polyoxyethylene polyoxypropylene ether, etc.

Examples of the water-soluble polymer include polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose and ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylic acid ester. Polymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein, etc. In addition to water-soluble polymers, polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, Len / emulsion and styrene / butadiene copolymer vinyl acetate copolymer, latexes such as styrene / butadiene / acrylic copolymer.

The ratio of the above-mentioned polymer dispersant or nonionic surface active agent used in combination with the anionic surface active agent is 0.05 to 1 part per 1 part of the anionic surface active agent to form fine particles and It is possible to contribute to the improvement of dispersibility and the stability of the dispersion liquid.

The volume average particle size and particle size distribution measuring method of the present invention are based on, for example, laser analysis / scattering method (Microtrack HRA9320-X100 type, Horiba L
A920 type, Rosentech FBRM apparatus), a centrifugal sedimentation method, a Coulter counter, an electron microscope, or the like, and can be used for measurement. Further, it is possible to increase the sensitivity by using a sensitivity improver together with a dye or a color developer.

The sensitivity improver used in the present invention includes:
The following are mentioned. Fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, fatty acid metal salts such as zinc stearate, aluminum stearate, calcium stearate, zinc palmitate and zinc behenate, p-benzyl Biphenyl, terphenyl, triphenylmethane, p
-Benzyl benzyloxybenzoate, β-benzyloxynaphthalene, phenyl β-naphthoate, phenyl 1-hydroxy-2-naphthoate, methyl 1-hydroxy-2-naphthoate, diphenyl carbonate, glare coal carbonate, dibenzyl terephthalate , Dimethyl terephthalate, 1,4-dimethoxynaphthalene, 1,4-
Diethoxynaphthalene, 1,4-dibenzyloxynaphthalene, 1,2-diphenoxyethane, 1,2-bis (3
-Methylphenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,4-diphenoxy-2-butene, 1,2-bis (4-methoxyphenylthio) ethane, dibenzoylmethane, 1,4 -Diphenylthiobutane, 1,4-diphenylthio-2-butene, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4-bis (2-vinyloxyethoxy) benzene, p- (2-
Vinyloxyethoxy) biphenyl, p-aryloxybiphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane,
Dibenzyl disulfide, 1,1-diphenylethanol, 1,1-diphenylpropanol, p-benzyloxybenzyl alcohol, 1,3-phenoxy-2-propanol, N-octadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoyl Benzene, 1,2-bis (4-methoxyphenoxy)
Propane, 1,5-bis (4-methoxyphenoxy)-
3-oxapentane, dibenzyl oxalate, bis (4-methylbenzyl) oxalate, bis (4-chlorobenzyl) oxalate and the like.

In order to produce the heat-sensitive recording material of the present invention,
When the above materials are bound and supported on a support, various commonly used binders can be appropriately used, and specific examples thereof include the following.

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid. Other than water-soluble polymers such as ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein, Polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer Emulsion and styrene / butadiene copolymers such as the body, styrene / butadiene / latex such as acrylic copolymer. As the filler material, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide can be used, and also a cross-linking material can be used. You can

As the support in the present invention, high-quality paper,
A support made of waste paper pulp (particularly, it is preferable to use waste paper pulp in an amount of 50% or more), synthetic paper, laminated paper and the like can be used. Further, an undercoat layer between the support and the thermosensitive recording layer or an overcoat layer may be provided on the thermosensitive recording layer. As the material for forming the undercoat layer or the overcoat layer, the binder, filler, cross-linking agent or the like used in the heat-sensitive recording layer can be used. It is particularly preferable to use hollow resin particles as a filler in the undercoat layer because the heat insulating property thereof can improve the sensitivity.

The hollow particles used in the present invention have a thermoplastic resin as a shell and contain air or other gas inside, and are fine hollow particles which are already in a foamed state and have a volume average particle diameter. Is 2 to 10 μm. If the volume average particle diameter (particle outer diameter) is smaller than 2 μm, there is a production problem such that it is difficult to obtain an arbitrary hollow ratio. On the contrary, if the volume average particle diameter is larger than 10 μm, the surface after coating and drying is smooth. As a result, the adhesiveness with the thermal head is reduced, and the sensitivity improving effect is reduced. Therefore, such a particle distribution is preferably such that the particle diameter is within the above range and the distribution peak is uniform with little variation.

Further, the hollow microparticles used in the present invention preferably have a hollowness of 50% or more, more preferably 70% or more. In addition, the hollow ratio referred to here is
The ratio of the outer diameter to the inner diameter of the hollow particles, which is expressed by the following formula. Hollow ratio = (inner diameter of hollow particles) / (outer diameter of hollow particles) × 1
00

The fine hollow particles used in the present invention have a shell of a thermoplastic resin as described above, and examples of the resin include polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate and polyvinyl resin. Examples thereof include acrylic acid ester, polyacrylonitrile, polybutadiene, isobornyl acrylate, acrylonitrile, methacrylonitrile, and copolymer resins thereof. In particular, a copolymer mainly composed of vinylidene chloride and acrylonitrile and a copolymer resin mainly composed of isobornyl acrylate, acrylonitrile and methacrylonitrile are preferable. Usually, the hollow particles are used as an intermediate layer between the thermosensitive coloring layer and the support to improve high heat insulation and adhesion to the head, thereby improving coloring sensitivity.

The recording method of the heat-sensitive recording material of the present invention is not particularly limited to a heating pen, a thermal head, laser heating, etc. depending on the purpose of use.

[0065]

EXAMPLES The present invention will now be described in more detail with reference to examples. The parts and% shown below are based on weight. The particle size was measured with LA-920 manufactured by Horiba Ltd. (1) Preparation of liquids A and B (dye dispersion liquid) 3-dibutylamino-6-methyl-N-7-anilino
A leuco dye dispersion was prepared by dispersing 30 parts of fluoran, a composition of the surfactant shown in Table 1, a silicone emulsion, and a polymer dispersant (dye content: 30%) under the dispersion conditions shown in Table 1. The sand mill is DYN for the sand mill.
OMILLType KDLPilot (manufactured by Backerfen), SC mill used SC-100 (manufactured by Mitsui Mining Co., Ltd.), ring mill used SRG-100 (manufactured by Araki Iron Works) spike mill used SHG-4 (manufactured by Inoue Seisakusho).

[0066]

[Table 1-1]

[0067]

[Table 1-2]

[0068]

[Table 1-3] For the evaluation of liquid fog, the current dispersion liquid (B-1) was compared,
X: Liquid fog is larger than (B-1), ◯: (B-1)
Less liquid fog, ◎: Almost no liquid fog,
Evaluated as.

From the results shown in Table 1, the dye dispersion of the present invention is
It is clear that a dispersion liquid free from liquid fog can be prepared with high productivity because the ratio of the extremely small particle components having a volume average particle diameter of 0.10 to 0.30 μm and 0.07 μm or less is 1% or less. is there.

(2) Preparation of liquid C (developer dispersion) (2) -14 20 parts of 4-isopropoxy-4'-hydroxydiphenyl sulfone, 10% aqueous solution of polyvinyl alcohol 20
Parts and 60 parts of water were dispersed by a sand mill to obtain a dispersion liquid having a volume average particle diameter of 0.81 μm. (2) -2 A polyester of 4-hydroxybenzoic acid (K-5 manufactured by Asahi Denka Kogyo Co., Ltd.) was used instead of 4-isopropoxy-4′-hydroxydiphenylsulfone of (2) -1. , (2) -1, and the volume average particle size is 0.95.
A μm dispersion was obtained. (2) -3 Same as (2) -1, except that a urethane urea compound (UD manufactured by Asahi Kasei Co., Ltd.) was used instead of 4-isopropoxy-4′-hydroxydiphenylsulfone of (2) -1. To obtain a dispersion liquid having a volume average particle diameter of 0.78 μm. (2) -4 A diphenylsulfonic acid derivative (D-90 manufactured by Nippon Soda Co., Ltd.) was used in place of 4-isopropoxy-4′-hydroxydiphenylsulfone of (2) -1.
A dispersion having a volume average particle size of 0.72 μm was obtained in the same manner as in (2) -1. (2) -5 Instead of 4-isopropoxy-4'-hydroxydiphenylsulfone of (2) -1, a compound having a sulfonylaminocarbonylamide group (Ciba Specialty Chemicals Co., Ltd. pergafast201) was used. A volume average particle diameter of 0.88 μm dispersion liquid was obtained in the same manner as in (2) -1. (2) -6 and (2) -1 except that 4,4′-dihydroxydiphenyl sulfone (bisphenol S) was used instead of 4-isopropoxy-4′-hydroxydiphenyl sulfone of (2) -1. Similarly, the volume average particle size is 0.88 μm
A dispersion liquid of was obtained. (2) -7 In place of 4-isopropoxy-4'-hydroxydiphenyl sulfone of (2) -1, 1,3,5-tris (6
-Isocyanatohexyl) -1,3,5-triazine-
A volume average particle diameter of 0.88 μm was obtained in the same manner as in (2) -1, except that an oligomer composition composed of 2,4,6- (1H, 3H, 5H) -trione and 4-aminosalicylic acid was used.
A dispersion was obtained.

(3) Preparation of Thermosensitive Coloring Coating Liquid Dye Dispersion A and Dye Dispersion B Liquid 20 parts, Developer Dispersion C Liquid 60 parts, colloidal silica (solid content 20%) 10
Parts, styrene butadiene latex (solid content 50%) 2
0 parts, stearic acid amide dispersion liquid (solid content 20%) 15
Parts, dioctylsulfosuccinic acid aqueous solution (solid content 5%) 1
To prepare a thermosensitive color developing layer coating liquid.

(4) Preparation of Undercoat Layer Forming Liquid (4) -1 Calcined Kaolin 20 parts Styrene / butadiene copolymer latex (solid content concentration 47.5%) 20 parts Water 60 parts (4) -2 Hollow resin particles 25 parts (hollowness 90%, volume average particle size 3.5 μm, solid content 40%) Styrene / butadiene copolymer latex (solid content concentration 47.5%) 15 parts Water 60 parts The above mixture is stirred and dispersed to give an under A coating layer forming liquid was prepared.

(5) Preparation of Overcoat Layer Forming Liquid Aluminum hydroxide 20 parts 10% polyvinyl alcohol aqueous solution 20 parts Water 60 parts The above mixture was dispersed by a ball mill for 24 hours to prepare (solution E).

Preparation of thermal recording paper On the paper having a basis weight of 60 g / m ² , the undercoat liquid shown in Table 2 was applied so that the dry coating amount would be 3.0 g / m ² , and dried. Then, a thermosensitive color-developing coating liquid was prepared by using the dye dispersion liquid and the color developer dispersion liquid shown in Table 2 above, and the coating liquid was dried so that the dye adhesion amount was 0.45 g / m ² , and further thereon. The resin was applied to the above so as to have a resin adhesion amount of 1.5 g / m ² and dried (the adhesion amount represents a dry adhesion amount). Then, it processed with the super calender and the thermal recording material of the Example and the comparative example was obtained.

[0075]

[Table 2]

Evaluation Method (Sensitivity Magnification) A calendered product was tested with a thermal printing experimental device having a thin film head manufactured by Matsushita Electric Parts Co., Ltd., head power 0.45 W / dot 1 line, recording time 20 msec /
L, scanning density 8 × 385 dots / mm, 1 ms
Prints with a pulse width of 0.0 to 0.7 mmsec for each ec,
The print density was measured with a Macbeth densitometer RD-914, and the pulse width at which the density became 1.0 was calculated. Using Comparative Example 1 as a reference, (pulse width of Comparative Example 1) / (measured sample pulse width) = sensitivity magnification is calculated. The larger the value, the better the sensitivity (thermal response). The evaluation results are shown in Table 3.

(Image Density) The calendered product was printed with a pulse width of 0.5 mmsec using the above-mentioned thermal printing experimental apparatus, and the printing density and background density were measured by Macbeth densitometer RD-9.
It was measured at 14.

(Heat resistance) The samples printed under the above conditions were left at 80 ° C. for 15 hours, and then the densities of the image area and the background area were measured.

(Heat and humidity resistance) The samples printed under the above conditions were allowed to stand at 40 ° C.-90% for 15 hours, and then,
The density of the image part and the background part was measured.

[0080]

[Table 3] From Table 3, the thermal recording material using the dye dispersion of the present invention,
It is clear that the thermal paper has high sensitivity, low background density, and excellent storage stability.

Next, basis weight 60 g / m^TwoTable 4 on the paper
Dry coating amount of 3.0 g / m using the undercoat liquid of^Two
It was coated so that Then add Table 4 on it
A heat-sensitive color-developing coating liquid using the above dye dispersion liquid and developer dispersion liquid.
Was added, and the amount of dye attached was 0.45 g / m^TwoTo be
After coating and drying, the amount of resin deposited on it is 1.5 g / m ^Two
Coated and dried (adhesion amount is dry adhesion amount
Represent). After that, process with Super Calendar,
Thermal recording material papers of Examples and Comparative Examples were obtained. Prepared heat sensitivity
The recording materials were evaluated as follows. (Color development sensitivity) Calendared products are manufactured by Matsushita Electric Parts Co., Ltd.
Head power in a thermal printing experimental device with a thin film head
0.45W / dot 1 line, recording time 20msec /
L, scanning density 8 × 385 dots / mm, 1 ms
Print with a pulse width of 0.0 to 1.2 msec for each ec
Character density was measured with Macbeth densitometer RD-914,
Was calculated to obtain a pulse width of 1.0. Based on Comparative Example 8
Then, (pulse width of Comparative Example 8) / (measured sample
Pulse width) = Sensitivity magnification, find the sensitivity magnification calculated as
I have The larger the sensitivity magnification value, the better the sensitivity (thermal response).
It means being good.

(Heat resistance test) A non-printed sample was
After leaving in the environment at 80 ° C. for 15 hours, the density of the non-printed portion was measured.

(Hunter whiteness of background area) With 10 sheets of non-printed samples stacked, the whiteness of the background area was measured with a digital Hunter whiteness meter (manufactured by Toyo Seiki Co., Ltd.). The results of each measurement are shown in Table 4.

[0084]

[Table 4] From the results shown in Table 4, the number of moles of polyoxyethylene in the surfactant having a polyoxyethylene group is 15 or less, and the terminal ether residue in the surfactant having a polyoxyethylene group is an alkyl group or an alkylphenyl group. Group, a phenylxylyl group, and a styrylphenyl group, the content of the particle size component of 0.07 μm or less in the leuco dye dispersion is 1% or less, and the surfactant is by weight with respect to the leuco dye. 5-25% content,
Further, by using a leuco dye dispersion having a volume average particle diameter of 0.10 to 0.30 μm, which is characterized by using a surfactant having a polyoxyethylene ether structure and a polymer dispersant as a dispersant, high sensitivity can be obtained. Therefore, it is clear that it is possible to provide a thermal paper having a high degree of whiteness of the background and excellent heat resistance of the background.

[0085]

EFFECTS OF THE INVENTION As is clear from the detailed and specific description above, the dye dispersion liquid of the present invention has good productivity in the dispersion method using a medium, and is free from liquid fog and liquid aggregation to form fine particles. Therefore, for example, when used in the production of thermal paper, it has high sensitivity and high whiteness of the background,
Further, it is possible to provide a thermal paper having excellent storage stability.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takeshi Kajikawa             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Shuji Miyamoto             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Yoshikazu Kaneko             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Yuichi Kawaguchi             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F term (reference) 2H026 AA07 BB25 BB26 BB28 BB30                       DD40 DD48 DD53 DD57 EE03                       HH03

Claims (26)

[Claims] 1. A leuco dye dispersion, characterized in that a leuco dye is dispersed by containing an anionic surfactant as a dispersant, and the volume average particle diameter of the leuco dye is 0.10 μm to 0.30 μm. liquid. 2. The leuco dye dispersion according to claim 1, wherein the volume average particle size of the dye particles in the leuco dye dispersion is in the range of 0.10 μm to 0.20 μm. 3. The leuco dye dispersion liquid according to claim 1, wherein an anionic surfactant having a polyoxyethylene group is used as a dispersant for the leuco dye dispersion liquid. 4. The number of moles of polyoxyethylene in the anionic surfactant having a polyoxyethylene group is 1.
It is 5 or less, The leuco dye dispersion liquid of Claim 3 characterized by the above-mentioned. 5. The anionic surfactant having a polyoxyethylene group is a saturated or unsaturated aliphatic hydrocarbon group, or an aryl group substituted with an unsubstituted or saturated or unsaturated aliphatic hydrocarbon group. The leuco dye dispersion according to claim 3, which has a terminal ether residue selected from the group consisting of: 6. 0.07 μm in said leuco dye dispersion
The leuco dye dispersion liquid according to any one of claims 1 to 5, wherein the content ratio of the following particle size components is 1% or less. 7. The leuco dye dispersion liquid according to claim 1, wherein an anionic surfactant is contained in the leuco dye in an amount of 5 to 20% by weight. 8. The leuco dye dispersion liquid according to claim 1, wherein the leuco dye contains 1 to 10% by weight of a silicon emulsion. 9. The leuco dye dispersion liquid according to claim 1, further comprising a polymer dispersant for the leuco dye. 10. The polymer dispersant is polyvinyl alcohol, polyacrylic sulfonic acid metal salt or partially saponified polyvinyl alcohol.
The leuco dye dispersion described in 1. 11. A dispersion method, characterized in that the leuco dye dispersion according to any one of claims 1 to 10 is obtained by carrying out sand mill dispersion using a glass medium having a diameter of 0.8 mm to 0.3 mm. 12. A dispersion method, characterized in that the leuco dye dispersion according to any one of claims 1 to 10 is obtained by carrying out sand mill dispersion using a zirconia media having a diameter of 0.8 mm to 0.3 mm. 13. A two-stage sand mill dispersion method comprising coarsely crushing using a medium having a diameter of 0.8 mm to 1.0 mm and then dispersing using a medium having a diameter of 0.5 mm to 0.3 mm. A leuco dye dispersion according to the present invention is obtained. 14. A dispersion method characterized in that the dispersion liquid according to any one of claims 1 to 10 is obtained by performing dispersion with an SC mill disperser using a zirconia media having a diameter of 0.8 mm to 0.3 mm. . 15. A dispersion method, wherein the dispersion liquid according to claim 1 is obtained by dispersing with a ring mill disperser using zirconia media having a diameter of 0.8 mm to 0.3 mm. 16. A dispersion method according to any one of claims 1 to 10, wherein dispersion is carried out by a spike mill disperser using zirconia media having a diameter of 0.8 mm to 0.3 mm. . 17. A heat-sensitive recording material having a heat-sensitive recording layer containing, as a main component, a leuco dye and a color developing agent which develops the color of the leuco dye when heated, on a support.
A heat-sensitive recording material produced by using the leuco dye dispersion obtained by the dispersion method according to any one of 1. 18. The thermal recording material according to claim 17, wherein an intermediate layer containing thermoplastic hollow resin particles is provided between the support and the thermosensitive coloring layer. 19. The thermosensitive recording material according to claim 17, wherein the color developer contains a (poly) 4-hydroxybenzoic acid derivative. 20. The heat-sensitive recording material according to claim 17, wherein the color developer contains a urea urethane compound. 21. The heat-sensitive recording material according to claim 17, wherein the color developer contains a diphenylsulfonic acid derivative represented by the following general formula. [Chemical 1] (In the formula, n represents 1 to 12.) 22. The heat-sensitive recording material according to claim 17, wherein the developer contains a developer having a sulfonylaminocarbonylamide group. 23. The heat-sensitive recording material according to claim 17, wherein the developer contains 4,4′-dihydroxydiphenyl sulfone (bisphenol S). 24. The heat-sensitive recording material according to claim 17, wherein the developer contains 4-isopropoxy-4′-hydroxydiphenyl sulfone. 25. An oligomer composition obtained by the polycondensation reaction of a trivalent or higher polyvalent isocyanate compound represented by the following general formula (I) and an aromatic amine represented by the formula (II), The heat-sensitive recording material according to claim 17 or 18, containing a substance. Embedded image X (NCO) a (I) embedded image (In the formula, X represents a group having a valence of 3 or more, and a represents an integer of 3 or more.
Further, b and c are integers of 0 to 5 and are combinations satisfying the relation that b + c is an integer of 1 to 5. Z represents a hydrogen atom, an alkyl group, an alkenyl group or an aryl group, and in the case of an aryl group, it also includes the case where a condensed ring structure is formed. d is an integer of 0 to 4 and is a combination that satisfies the relationship of being an integer of b + c + d = 1 to 5 (where b + c = 1 to 5). ) 26. The heat-sensitive recording material according to claim 17, wherein the support is made of waste paper pulp.