JPH03169355A - Method for wet pulverization of organic solid substance and recording material coated with aqueous dispersion of fine particle of organic solid substance - Google Patents

Abstract

PURPOSE:To enhance pulverization efficiency by continuously grinding an aqueous dispersion of an org. solid substance using a plurality of sand mills constituted so that the diameter of the grinding media used in the sand mill of a later stage is made smaller than that of the grinding media used in the sand mill used in an earlier stage. CONSTITUTION:A plurality of sand mills constituted so that the diameter of the grinding media used in the sand mill of a later stage is made smaller than that of the grinding media used in the sand mill of an early stage are arranged. An aqueous dispersion of org. solid substances such as org. pigment, an org. dye, an org. coupler or an org. heat-meltable substance is continuously subjected to wet pulverization using a plurality of the sand mills. The diameter of the opening part of a separation mechanism part separating the aqueous dispersion and grinding media in each of the sand mills is pref. 3/5-2/5 the diameter of the grinding media. The aqueous dispersion containing the fine particles of pulverized org. solid substances is applied to a support and dried to form a thermal recording material.

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a wet pulverization method for organic solid substances, and more particularly to a method for efficiently wet pulverization of an aqueous dispersion of an organic solid substance using various types of sand mills filled with grinding media. The present invention also relates to an aqueous dispersion of an extremely uniformly finely divided organic solid substance, and various recording media such as heat-sensitive recording media and pressure-sensitive copying paper that have high quality obtained by coating the aqueous dispersion. It is. "Prior Art" Various types of organic solid substances such as organic pigments, organic dyes, and organic solid substances are used in various types of recording media such as heat-sensitive recording media and pressure-sensitive copying paper. It is desirable to use it as a finely divided aqueous dispersion as much as possible. Various methods are known for micronizing organic solid substances. For example, a solution obtained by dissolving an organic solid substance in a good solvent is added to a poor solvent for the organic solid substance to reprecipitate the organic substance. A method in which a solution obtained by dissolving an organic solid substance in a solvent is emulsified in another solvent using an emulsifying machine such as a homogenizer, and then the solvent is removed by distillation to make it fine. A method in which the organic solid substance is directly dissolved in a hammer mill or ball mill. , a dry grinding method using a grinder such as a jet stream mill, a method in which an organic solid substance is dispersed in water or a solvent, and then the organic solid material is dispersed in a sand grinder, ball mill, etc.
A method of wet grinding using a grinder such as an attriter, or a method of dispersing an organic solid substance in water or a solvent, heating it above the melting point of the organic substance, and then using a grinder such as a sand grinder, ball mill, attritor, or homogenizer. A method of wet pulverization using an emulsifier has been proposed. These micronization methods are selected and used as appropriate depending on the type of organic solid substance, the desired degree of micronization, etc., but since the use of an organic solvent is essential in the method of dissolving the organic solid substance in a solvent. However, there are problems in terms of safety, economy, etc. Furthermore, if the average particle size of the organic solid substance is 10 μm or less, dry pulverization poses a risk of dust explosion, so wet pulverization is preferably employed. "Problems to be Solved by the Invention" Various organic solid substances such as organic pigments, organic dyes, and organic solid substances used in various recording media such as heat-sensitive recording media and pressure-sensitive copying paper are generally It is used after being miniaturized to a size of 1 μm or less, but in recent years, with the remarkable increase in speed of recording equipment, there has been a demand for a significant improvement in recording sensitivity.In particular, in thermal recording media, organic dyes and organic color developers are finely divided to 1 μm or less. There is a demand for ultra-fine design down to about 0.3 μm. However, in various sand mills filled with grinding media, which is the most common grinder used in the wet grinding method,
Although it is possible to make particles as fine as 1 μm or less, it is not easy to grind them to fine particles of 1 μm or less, and the current situation is that a very long grinding process is required. In view of the current situation, the inventors of the present invention have conducted intensive research on a method for efficiently wet-pulverizing various organic solid materials using a sand mill filled with grinding media, and have found that the method of wet-pulverizing various organic solid substances efficiently has the following results: If the diameter of the media is used differently, that is, as the diameter of the organic solid particles becomes finer in the range from coarse to ultra-fine pulverization, the pulverization process is carried out using a sand mill filled with pulverizing media that satisfies specific conditions for each sand mill. When this is done, the atomization efficiency is extremely remarkable, and the opening of the separation mechanism of the grinding media is specified to 3/5 to 2/5 of the diameter of the grinding media, and the dispersant is added in parts in each sand mill area. By doing so, the separation efficiency of fine media and liquid is improved, and even in the case of fine slits and narrow opening screens, separation is extremely good, there is no breakdown of the separation mechanism, and the process is uniformly ultra-fine in a short time. Furthermore, when the aqueous dispersion of the ultrafine organic solid material thus obtained is applied to various recording media, products with extremely high sensitivity (high concentration) can be obtained. As a result, the present invention was completely abandoned. "Means for Solving the Problems" The present invention provides a method for continuously wet-pulverizing an aqueous dispersion of an organic solid substance using a plurality of sand mills, in which the diameter of the grinding media used in the subsequent sand mill is A method of wet pulverization of an organic solid substance characterized by making the material finer than that of the previous sand mill, and a recording medium coated with an aqueous dispersion containing fine particles of the organic solid substance obtained by pulverization in this manner. "Operation" The sand mill used in the present invention is a variety of sand mills whose interior is filled with fine beads called grinding media. A specific example of such a sand mill is a stirring tank such as an attritor or a sentry mill, in which media such as glass beads, ceramic balls, steel balls, etc. and a processing dispersion liquid are placed together in a stirring tank and stirred with a vertical arm from above. Sand grinder: A vertical or horizontal cylindrical tank equipped with a shaft with a disk or bottle inside is filled with media, and the processing dispersion liquid is continuously fed into this tank to carry out the grinding process. There are flow tube type mills such as grain mills, pearl mills, matter mills, dyno mills, etc. Conventionally, when processing aqueous dispersions of organic solid substances using these wet grinders, the same types of grinders are connected in series or parallel, and the grinding media used in the grinders are of the same type and the same type. It is common to use one with a certain size (average diameter). In order to increase the degree of pulverization, the material is repeatedly pulverized using the same type of pulverizer, or a plurality of pulverizers are arranged in series and the pulverizers are used to process the same type of pulverizer. However, although it is possible to refine particles to a certain extent with this method, it is not easy to obtain particles that are uniformly refined to 1 μm or less.
Even if repeated pulverization is performed using a flow tube type sand mill filled with 90 kg of glass beads with a diameter of 1.5 to 2.0 mm, the pulverization process takes an extremely long time to obtain fine particles of approximately 1.5 μm or less. This requires the use of more than 10 pulverizers, which is unproductive and poses a serious problem in practice. To this end, methods that have been adopted to promote fine pulverization and ultrafine pulverization include increasing the filling rate of the grinding media filled inside the vessel, increasing the rotation speed of the disk, and changing the material of the grinding media. One method is to use zirconia beads, metal beads, etc., which have as high a specific gravity as possible, for example, instead of glass beads, but all of them have problems, and there is still room for improvement. In other words, if the filling rate of the grinding media is increased, the movement of the media will not be smooth in proportion to it, and the load on the rotational power of the disk will increase.On the other hand, if the rotation of the disk is increased, the power load will increase and the amount of grinding liquid will increase. It is not desirable as it causes fever etc. Furthermore, in the case of beads made of zirconia or metal, there are problems such as high cost and mackerel. Regarding the size (diameter) of the pulverizing media, although the pulverization efficiency may be extremely remarkable when using fine media, the efficiency is not always high. For example, a flow tube type sand mill with a vessel capacity of 100 liters has a diameter of 1.
Diameter 0.5-0 instead of 5-2.0 mm glass beads
．． If 64S+A glass beads are used for coarse pulverization, the pulverization efficiency will be poorer and the separation mechanism will become clogged, which is not preferable. In addition, an aqueous dispersion with an average particle size of 1.6 pm that has been coarsely pulverized is mixed with a diameter of 0.6 to 0.
．． When pulverization is carried out using 8I11I1 glass beads, it can be very efficiently pulverized up to an average particle diameter of about 0.8 μm in the aqueous dispersion; Further refinement is extremely poor. However, the aqueous dispersion of micronized particles with an average particle diameter of about 0.8 μm that has been micronized in this way is ultrafinely pulverized using grinding media with a finer diameter, for example, 0.3 to 0.5 n+m. When treated, extremely efficient pulverization is possible, and pulverization of down to about 0.4 μm is possible on an industrial scale. Conventionally, when wet-pulverizing organic solid materials, a dispersant is added to water, organic solid powders such as dyes and color developers are added to this, and the mixture is stirred with a general propeller ξ mixer to form the liquid before milling. However, this solution contains coarse particles (50 to 200 μmφ).
If you try to process this liquid from the beginning with a sand mill compatible with micro media, it will clog the narrow media separation mechanism, increasing the pressure inside the mill vessel, and causing the vessel rotating shaft sealing mechanism to become clogged. Coarse pulverization is difficult with a sand mill compatible with fine media, which is effective for fine pulverization, as problems such as breakage and an increase in the temperature of the dispersion in the fruit occur. On the other hand, as mentioned above, it is impossible to produce fine grains of ltIII+ or less on an industrial scale with conventionally used sand mills that are compatible with grinding media with a diameter of 1.5 to 2.0 mm+, which is capable of coarse grinding. . In light of the above-mentioned circumstances, the present inventors conducted extensive research on the size of the grinding media and the grinding efficiency, and found that when the diameter of the solid material to be ground is large at the initial stage of grinding, the diameter of the grinding media used for grinding is use a large one,
It has been found that as the diameter of the solid material to be ground is made finer by the pulverizing action, the diameter of the grinding media used can be changed to a finer one, thereby promoting pulverization very efficiently. The reason why pulverization is carried out so efficiently is not necessarily clear, but it is presumed as follows. In other words, when the diameter of the solid material to be crushed is large, it is efficient to apply large impact energy to the solid material using relatively large crushing media to perform coarse crushing. This results in energy loss, consumes power and time, and has poor grinding efficiency. On the other hand, if large grinding media are used for small solid particles, it is presumed that the solid particles are relatively small and the grinding action of the grinding media does not work efficiently on the small particles, resulting in inefficiency. Therefore, in the present invention, as pulverization (the solid particle size becomes finer) progresses, the diameter of the pulverizing media is made finer at each stage, thereby promoting pulverization extremely efficiently. It is. Accordingly, in the method of the present invention, when ultrafinely pulverizing an organic solid substance, the diameter of the pulverizing media used in the sand mill is adjusted to the following (1) or (II) according to the decrease in the average particle diameter of the water-decomposed liquid to be pulverized. ) formula, immediately d2 ≦ 0.9 (n) d+ where D; average diameter of grinding media (llIll) dI; average particle diameter of organic solid material at the entrance of the sand mill (μo
+) d2; Average particle diameter (μm) of the organic solid substance at the exit of the sand mill (however, D < 5 mmd, dr < 15μ
-. ), it is possible to significantly increase the pulverization efficiency in each area of coarse pulverization, fine pulverization, and ultra-fine pulverization.
An aqueous dispersion of a uniformly ultrafine organic solid substance can be obtained on an industrial production scale in a short period of time. The reason why the pulverization efficiency is so remarkable when using fine media in a sand mill is not necessarily clear, but it is thought that the difference in the number of media due to the difference in media diameter for the same vessel volume makes a large contribution. It will be done. For example, the media diameter is 1.5 mm and 0.5 nm.
+mφ has about 30 times more media,
It is presumed that this improves the pulverization efficiency. Normally, when an aqueous dispersion of an organic solid substance is pulverized using a sand mill filled with pulverizing media, the media becomes abraded as the organic solid substance becomes finer, and the diameter of the media becomes smaller. Media that has become smaller due to wear and tear may get stuck in the slits of the separation mechanism or the openings of the screen, causing the screen to become clogged. This is because in commonly used sand mills, the screen and slit openings are set to 1/3 of the media diameter.
This is because the aperture of the separation mechanism is set to such a degree that it is possible to separate the aqueous dispersion and the media even if the media is considerably abraded. However, when the diameter of the grinding media is about 1.5 mm, the passage of the aqueous dispersion is good even if the opening of the separation mechanism is set to 0.5 mm, but the diameter is 0.5 mm, which is effective for ultra-fine grinding.
When using grinding media of about 3 mm, the opening is 1/
3, and as a result, the passage of the aqueous dispersion is markedly reduced, so it is difficult to handle a large amount of the pulverizing liquid. As a result of numerous experiments regarding the diameter of the grinding media and the aperture of the separation mechanism, the inventors of the present invention have found that when the aperture is set to a grinding media (3) sand mill, more preferably around 3/5, the aperture becomes extremely small at 0.3. It was found that even when using a meφ media, the aqueous dispersion passed smoothly, and even if the media was worn out and its diameter became smaller, there was no problem with continuous operation for about 3 to 4 weeks. In order to obtain an aqueous dispersion of an organic solid substance, various dispersants are used. Examples of such dispersants include polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, acrylic acid derivatives, sulfonic acid derivatives, and maleic anhydride. One or more types of surfactants such as acid derivatives, various water-soluble polymer compounds such as gelatin, and various surfactants such as anionic surfactants and nonionic surfactants are appropriately selected and used. The amount of dispersant added to the aqueous dispersion is preferably the minimum necessary amount. However, wet grinding by a mill increases the surface area of the organic solid material, and the amount of dispersant required increases as the grinding progresses. Therefore, it is preferable to additionally add a dispersant during the pulverization process. On the other hand, depending on the type of dispersant, the fluidity form of the aqueous dispersion may change. For example, polyvinyl alcohol has a large dispersing power, but if added in a large amount, it becomes giratant fluid. On this point, methylcellulose-based materials are weak against mechanical shearing force, but exhibit pseudoplastic flow, and have the advantage of not increasing viscosity even at high shear rates, and are suitable for media separation mechanisms with small openings. It does not cause clogging and is one of the preferred dispersants. According to the study results of the present inventors, sand

[Rather than adding the entire amount of dispersant to an aqueous dispersion of organic solid substances from the beginning when processing with a mill, it is preferable to add the dispersant in portions. When wet milling is used, 40 to 60% by weight of the total dispersant required is added just before coarse milling with a sand mill, and the remaining dispersant is added to the organic solid just before each mill. Foaming and thickening phenomena (sludge) occur when the substance is added in parts to an aqueous dispersion.
It has become clear that miniaturization can be achieved extremely efficiently without problems such as clogging in thin separation mechanisms. Of course, when adding the dispersant, it is possible to adopt a method of adding the dispersant in addition to the method described above, which improves efficiency by further dividing the dispersant. The organic solid substances to be pulverized in the method of the present invention include various solid organic substances, and in particular, organic pigments, organic dyes, etc. used in various recording bodies such as heat-sensitive recording bodies and pressure-sensitive copying papers, When the method of the present invention is applied to the miniaturization of various organic substances such as organic color developers and organic thermofusible substances, extremely remarkable effects can be obtained. Note that the method of the present invention can also be applied to the miniaturization of liquid substances that become solid by lowering the temperature. Various organic dyes are known for use in thermal recording media, pressure-sensitive copying paper, etc. For example, 3,3-bis(p-dimethylaminophenyl) is a colorless to light-colored basic dye. )-6-dimethylaminophthalide, 3.3
-bis(p-dimethylaminophenyl)phthalide, 3-
(p-dimethylaminophenyl)-3-(1,2-dimethylindol-3-yl)phthalide, 3-(p-dimethyla4nophenyl)-3-(2-methylindol-3-yl)phthalide, 3,3 -bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindole-3)
-yl)-6-dimethylaminophthalide, 3.3-bis(9-ethylcarbazol-3-yl)-6-dimethylagonophthalide, 3.3-bis(2-phenylindol-3-yl)- 6-dimethylanophthalide, 3-p
-Triallylmethane dyes such as dimethylaminophenyl-3-(1-methylvirol-3-yl)6-dimethylaminophthalide, 4.4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl leuco auramine, N-2.4.5-} diphenylmethane dyes such as dichlorophenyl leuco auramine, thiazine dyes such as penzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, 3-methyl-spirodinaphthobilane, 3- Ethyluth birosinaphthopyran, 3-phenyluth birosinaphthopyran,
3-pendylose spirodinaphthopyran, 3-methylnaphtho(6'-methoxybenzo)spiropyran, 3-
Spiro-based dyes such as propylose spirodibenzobilane,
Lactam dyes such as rhodamine-B anilinolactam, rhodamine (p-nitroanilino) lactam, rhodamine (O-chloroanilino) lactam, 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-6
-Methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7,8-penzofluorane , 3-diethylamino-5-methyl-7-dibenzylaminofluorane, 3-diethylamino-6.7-
Dimethylfluorane, 3-(N-ethyl-P-toluidino)-7-methylfluorane, 3-diethylamino-7
-N-acetyl-N-methylaminofluorane, 3-diethylamino-7-N-methylaminofluorane, 3-
Diethylamino-7-dibenzylaminofluorane, 3
-diethyl-N-benzyl-7-N-methyl-N-benzyl ξ
Nofluorane, 3-diethylamino-7N-chloroethyl-N-methylaminofluorane, 3-diethylamino7-N-diethylaminofluorane, 3-(N-ethyl-p-}luidino)-6-methyl-7-phenylamino Fluoran, 3-(N-cyclopentyl-N-ethylano)-6-methyl-7-anilinofluorane, 3-
(N-ethyl-p-}luidino)-6-methyl-7-(
p-}Louisino) fluorane, . 3-diethylamino-6-methyl-7-phenylaminofluorane, 3-diethylamino-7-(2-carbomethoxyphenylamino)fluoran, 3-(N-ethyl-N-isoarξruaξno)-6- Methyl-7-phenylaminofluorane,
3-(N-cyclohexy-N-methylamino)-6-
Methyl-7-phenylaminofluorane, 3-pyrrolidino-6-methyl-7-phenylaminofluorane, 3-
Piperidino-6-methyl-7-phenylaξnofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, 3-diethylamino-7-(o-chlorophenylaξno)fluorane, 3-dibutylamino-7-
(o-chlorophenylamino)fluoran, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, 3-N-methyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran, 3-N
Examples include fluoran dyes such as -ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane. In addition, various organic color developers that develop color upon contact with basic dyes are known, such as 4-tert-butylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 4-hydroxy Acetophenol, 4-tert-octyltecol, 2.2'-
Dihydroxydiphenol, 2,2'-methylenebis(
4-methyl-6-tert-isobutylphenol)
, 4.4'-isopropylidene bis(2-tart
-butylphenol), 4.4'-sec-butylidene diphenol, 4-phenylphenol, 4,4'
-isobropylidene diphenol (bisphenol A)
, 2.2'-methylenebis(4-chlorophenol), hydroquinone, 4.4'-cyclohexylidene diphenol, benzyl 4-hydroxybenzoate, dimethyl 4-hydroxyphthalate, hydroquinone monobenzyl ether, 4-hydroxyphenyl- Phenolic compounds such as 4'-isoprobyloxyphenyl sulfone, novolac type phenolic resin, phenol polymer, benzoic acid, p-tert-butylbenzoic acid, trichlorobenzoic acid, terephthalic acid, 3-secbutyl-4-hydroxybenzoic acid acid, 3-cyclohexyl-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid,
Salicylic acid, 3-isobrobylsalicylic acid, 3-ter
t-butylsalicylic acid, 3-pendylsalicylic acid, 3-
(α-methylbenzyl)salicylic acid, 3-chloro-5-
(α-methylbenzyl)salicylic acid, 3,5-diter
t-butylsalicylic acid, 3-phenyl-5-(α,α
- Aromatic carboxylic acids such as dimethylbenzyl)salicylic acid, 3.5-di-alpha-methylbenzylsalicylic acid, and these phenolic compounds, aromatic carboxylic acids such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel. Examples include organic acidic substances such as salts with polyvalent metals such as . Furthermore, organic thermofusible substances include, for example, waxes such as zinc stearate, calcium stearate, polyethylene wax, carnauba wax, paraffin wax, and ester wax, stearic acid amide, stearic acid methylene bisamide, oleic acid ξ-do, and valmitine. Fatty acid amides such as acid amides and coconut fatty acid amides, 2,
2°-Methylenebis(4-methyl-5-tert-butylphenol L4,4'-butylidenebis(6-te
rt-butyl-3-methylphenol), 1,1.3
-}Lis(2-methyl-4-hydroxy-5-t
Hindered phenols such as ert-butylphenol)butane, 2-(2'-hydroxy-5'-methylphenyl)penzotriazole, 2-hydroxy=4-
UV absorbers such as penzyloxybenzophenone, dibenzyl terephthalate, 1,2-di(3-methylphenoxy)ethane, 1,2-diphenoxyethane, 1-phenoxy-2-(4-methylphenoxy)ethane, 4.4
'monoethylenedioxybisbenzoic acid shifthenyl methyl ester, terephthalic acid dimethyl ester, terephthalic acid dibutyl ester, terephthalic acid dibenzyl ester, p-pendylubiphenyl, l,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, Various known ones such as 1-hydroxynaphthoic acid phenyl ester can be mentioned. In the various aqueous dispersions of organic solid substances obtained by the method of the present invention, the organic solid substances are extremely uniformly finely divided.
It is effectively used in a wide range of technical fields, including various recording media such as heat-sensitive recording media and pressure-sensitive copying paper. In particular, when applied to heat-sensitive recording materials that require a strong demand for fine grained materials, extremely excellent recording sensitivity can be obtained, making it one of the most effective embodiments by applying the method of the present invention. be. Note that as long as the aqueous dispersion of the organic solid material finely divided by the method of the present invention is used, the method for producing the heat-sensitive recording material is not particularly limited, and various known methods can be appropriately selected and applied. Incidentally, the usage ratio of the basic colorless dye and color developer in the recording layer is generally about 1 to 50 parts by weight, preferably about 1 to 10 parts by weight, per 1 part by weight of the basic colorless dye. In addition to basic colorless dyes and color developers, adhesive components such as starch, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, gum arabic, polyvinyl alcohol, diisobutylene, etc. Maleic anhydride copolymer salt, styrene/maleic anhydride copolymer salt, ethylene/acrylic acid copolymer salt, styrene/acrylic acid copolymer salt, natural rubber emulsion, styrene/butadiene copolymer emulsion, acrylonitrile・Butadiene copolymer emulsion, methyl methacrylate/butadiene copolymer emulsion, polychloroprene emulsion digon, vinyl acetate emulsion, ethylene/vinyl acetate emulsion, etc. are added. In addition, as a pigment,
For example, diatomaceous earth, calcined diatomaceous earth, kaolin, calcined kaolin,
Inorganic pigments such as white carbon, magnesium carbonate, calcium carbonate, zinc oxide, aluminum oxide, titanium oxide, silicon oxide, aluminum hydroxide, barium sulfate, zinc sulfate, talc, clay, calcined clay, styrene micropol, nylon powder , polyethylene powder,
Urea/formalin resin fillers, organic pigments such as raw starch granules, etc. are added, but of course the materials are not limited to these exemplified substances, and it is also possible to use two or more types in combination as necessary. . Furthermore, various other auxiliary agents can be appropriately added to the recording layer coating solution, such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate,
Dispersants such as sodium lauryl alcohol sulfate ester, alginates, fatty acid metal salts, various heat-fusible substances as described above, antifoaming agents, fluorescent dyes, color dyes, etc., may be used. The method of forming the recording layer is not particularly limited either, and the recording layer coating liquid may be applied onto the support using an appropriate coating device such as an air knife coater, blade coater, roll blade, bar coater, gravure coater, or multilayer coater. The shape is determined by the method of drying. The amount of coating liquid applied is not particularly limited, and is generally 2 to 12 g/rr in terms of dry weight.
It is adjusted to about r, preferably in the range of about 3 to 10 g/rd. The support is not particularly limited, and may include paper such as high-quality paper, base paper made with a Yankee machine, single-sided glossy base paper, double-sided glossy base paper, cast coated paper, art paper, coated paper, medium-quality coated paper, etc. Fiber paper, synthetic resin film, etc. are used as appropriate. In addition, after coating and drying the recording layer, smoothing treatment such as super calendering may be performed as necessary, a single layer of overcoat 1 may be provided on the recording layer for the purpose of protecting the recording layer, etc. Various known techniques in the field of heat-sensitive recording materials can be added, such as providing an undercoat layer or a backcoat layer. The heat-sensitive recording material of the present invention obtained in this way has extremely good recording sensitivity and high-speed recording because it uses a uniformly finely divided aqueous dispersion of a basic dye, a color developer, a thermofusible substance, etc. It has excellent characteristics that make it suitable for recording. "Examples" The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these Examples. Further, unless otherwise specified, parts and % in the examples represent "parts by weight" and "% by weight", respectively. Example 1 [Fine pulverization treatment of basic dye dispersion] 3-dibutylano-6-methyl-7-phenylagonofluorane 100 parts 1,2-bis(
250 parts of 3-methylphenoxy)ethane 200 parts of 2% water fJ solution of methylcellulose 10 parts of sodium di(tridecyl)sulfosuccinate
An aqueous dispersion of basic dye consisting of 200 parts was prepared in a dispersion tank, and the aqueous dispersion thus prepared was milled in a sand mill (trade name: Grenkle GMH-S).
50M/manufactured by Asada Tekko Co., Ltd.) six units are arranged in series, with a flow rate of 18
Fine pulverization treatment was performed by continuously passing through six machines at a rate of 0 kg/hour. The conditions for each wheel at this time (material of the grinding media, average particle diameter, filling rate, opening of the separation mechanism, peripheral speed of the rotor, etc.) are shown in Table 1. Note that the average particle diameter of the grinding media was determined by using sequentially finer glass beads according to the order in which the grinding liquid passed. Also, immediately before each mill from the second mill onward, a 10% aqueous solution of polyvinyl alcohol (degree of saponification 88%, degree of polymerization 1000, surface tension 53 dyne/cm, residual acetic acid groups are in the form of blocks) was added to the organic solid substance aqueous dispersion.
Continuous addition was carried out using a metering pump so that the amount reached 0 parts. In this way, serial wet continuous pulverization was performed to obtain an aqueous dispersion of a basic dye having an average particle size as shown in Table 1. Example 2 In Example 1, the flow rate of the aqueous dispersion to be pulverized was set to 24
Series wet continuous pulverization was carried out in the same manner except that the pulverization rate was 0 kg/hour to obtain an aqueous dispersion of a basic dye having an average particle size as shown in Table 1. Comparative Example 1 Except that the coarse grinding media used in the first sand mill in Example 1 was used in all six sand mills,
Grinding treatment was carried out in the same manner. In this case, pulverization to an average particle size of 1 μm or less was impossible. Comparative Example 2 Grinding was carried out in the same manner as in Example 1, except that the finest grinding media used in the sixth sand mill was used in all six sand mills. In this case, the passage holes (openings) of the separation mechanism in the first sand mill device became clogged, making it impossible to perform a satisfactory pulverization process. Comparative Example 3 In Example 1, the entire amount of the required dispersant was added in advance in the process of preparing the aqueous dispersion of the basic dye. The dispersion thus obtained was passed through a sand mill in the same manner as in Example 1, in which the particle size of the grinding media was made finer as the dispersion passed. Furthermore, when no dispersant was added during the process, the pulverization efficiency was extremely reduced. Example 3 [Fine pulverization treatment of color developer dispersion] 4-hydroxy-4"-isoproboxydiphenyl sulfone 400 parts 2% aqueous solution of methyl cellulose 200 parts dioctyl sodium sulfosuccinate 5 parts water
An aqueous dispersion of a color developer consisting of 250 parts was prepared in a dispersion tank, and the prepared aqueous dispersion was subjected to a flow rate of 18% under the same conditions as in the case of the basic dye dispersion applied in Example 1.
Fine pulverization was performed by continuously passing through six mills at a rate of 0 kg/hour to obtain an aqueous developer dispersion having an average particle size as shown in Table 2. Example 4 The aqueous dispersion was pulverized in the same manner as in Example 3, except that the flow rate of the aqueous dispersion to be pulverized was changed to 240 kg/hour. The average particle diameter of the obtained aqueous developer dispersion is shown in Table 2. Comparative Example 4 In Example 3, except that the coarse grinding media used in the first sand wheel was used in all six sand wheels,
Grinding treatment was carried out in the same manner. Table 2 shows the average particle diameter of the color developer water-resolved liquid obtained at this time. Comparative Example 5 Grinding was carried out in the same manner as in Example 3, except that the finest grinding media used in the sixth sand mill was used in all six sand mills. In this case, the passage holes (openings) of the separation mechanism in the first sanding apparatus became clogged, and a satisfactory pulverization process could not be achieved. Comparative Example 6 In Example 3, the entire amount of the required dispersant was added in advance in the process of preparing the aqueous dispersion of the color developer. The thus obtained dispersion was passed through a sand mill in the same manner as in Example 3, in which the particle size of the grinding media was made finer as the dispersion passed. or,
The pulverization treatment was performed without any additional addition of a dispersant during the process. The results at this time are shown in Table-2. The average particle size of the dye and developer is MICROTRA.
C PARTICLE SIZE ANALYZER
(manufactured by LEED & NORTHRUP COMPANY). In addition, the fluidity of the aqueous dispersion was visually observed and evaluated using the following evaluation criteria, and the results are shown in Table 1 and Table 2. [Fluidity of the pulverized liquid of the aqueous dispersion] ◎...Very good O...Good Δ...Slightly poor (slightly muddy) Example 5~
6. 712 parts of the color developer dispersion obtained in Comparative Example 4, 1000 parts of a 10% aqueous solution of methyl methacrylate/acrylamide copolymer, and 100 parts of amorphous silicon oxide were added to this liquid in a dispersion tank using a propeller mixer. After stirring and adding 30 parts of a 30% aqueous dispersion of zinc stearate,
Added 826 parts of the aqueous dispersion of basic dye obtained by the methods of Example 1 and Example 2 (Example 5 and Example 6, respectively).
) and stirred to prepare a coating solution for thermal recording paper. Next, 10 g of amorphous silicon oxide was added to the base of 50 g/rd.
0 parts of water, 10 parts of styrene-butadiene copolymer latex (solid content), and 2 parts of carboxymethyl cellulose (solid content) at a concentration of 35%. ? Rl was coated and dried using a blade coater so that the coating amount after drying was 7 g/+a. After drying the above coating liquid for heat-sensitive recording paper on this coating layer surface using a blade coater, the coating amount was 3.6 g.
The coated sheets were coated and dried so that the surface of the heat-sensitive recording layer had a smoothness of 450 seconds, and then smoothed using a super calender so that the Bekk smoothness of the surface of the heat-sensitive recording layer was 450 seconds to obtain two types of heat-sensitive recording paper. Examples 7 to 8 In Examples 5 and 6, 578 parts of the basic dye aqueous dispersion obtained by the method of Example 1 and Example 2 were added (Example 7 and Example 8, respectively). ), Example 5
Two types of thermal recording paper were obtained in the same manner as in Example 6. Examples 9 to 10 In Examples 5 and 6, the developer dispersion liquid obtained in Example 3 was replaced with that obtained in Comparative Example 4.
Using 498 parts of each of I, and Example 1 and Example 2
The aqueous dispersion of basic dye obtained by the above method was changed to 578 parts, and the coating amount of the coating liquid for thermal recording paper was changed to 3.
Two types of thermal recording paper were obtained in the same manner as in Example 5 and Example 6, except that the coating was applied at 2 g/bo (Example 9 and Example 10, respectively). Comparative Example 7 A thermosensitive recording paper was obtained in the same manner as in Example 5, except that the dye of Comparative Example 1 was used instead of the aqueous dispersion of the basic dye of Example 1. Comparative Example 8 In Comparative Example 7, except that the aqueous dispersion of the salt removal dye obtained by the method of Comparative Example 1 was reduced to 578 parts, and the color developer obtained in Comparative Example 4 was reduced to 498 parts. A thermosensitive recording paper was obtained in the same manner as in Comparative Example 7. [Evaluation of thermal recording paper} The thus obtained thermal recording paper was recorded using a commercially available thermal facsimile machine (product name: NIEFAX-2, manufactured by NEC Corporation), and the recorded density was measured using a Macbeth densitometer. The results obtained are shown in Table-3. "Effects" As is clear from the viscous in the table, when the method of the present invention is used to finely crush the particles, there is no problem with the media separation mechanism, the average particle diameter is extremely small compared to the comparative example, and the fluidity is stable. Thermal recording paper produced using the crushed dye and/or coloring agent exhibited excellent recording sensitivity and extremely high recording density.

Claims (7)

[Claims] (1) A method of continuously wet-pulverizing an aqueous dispersion of an organic solid substance using multiple sand mills, characterized in that the diameter of the grinding media used in the later stage sand mill is made smaller than that of the earlier stage sand mill. A wet pulverization method for organic solid materials. (2) The wet pulverization method for an organic solid substance according to claim (1), wherein the diameter of the grinding media satisfies the following formulas [I] and [II] at the same time. d_1>1.4D/1000≧d_2 [I]d_2/
d_1≦0.9 [II] In the formula, D: Average diameter of the grinding media (mm) d_1: Average particle diameter of the organic solid substance at the entrance of the sand mill (μm) d_2: Average of the organic solid substance at the exit of the sand mill Particle diameter (μm) (However, D<5mm, d_1<15μm.) (3) The opening (opening) of the separation mechanism that separates the aqueous dispersion and the grinding media in a sand mill is 3/3 of the diameter of the grinding media.
The method for wet pulverization of an organic solid substance according to claim 1 or 2, wherein the pulverization ratio is 5 to 2/5. (4) Claim that the dispersant is added in portions to the aqueous dispersion (
1) The method for wet pulverization of an organic solid substance as described above. (5) Claim in which the organic solid substance is an organic pigment, an organic dye, an organic color developer, an organic thermofusible substance, or a mixture thereof (
1) The method for wet pulverization of an organic solid substance as described above. (6) A recording medium coated with an aqueous dispersion containing fine particles of an organic solid substance finely pulverized by the method of claims (1) to (5). (7) The recording material according to claim (6), wherein the recording material is a heat-sensitive recording material.