JP3373572B2 - Method for producing liquid developer for electrostatic image development - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a liquid developer for developing an electrostatic charge image, which is applied to manifest an electrostatic charge image.

[0002]

2. Description of the Related Art Conventionally, a liquid developer has been used as a method of developing an electrostatic charge image formed on an electrostatic latent image carrier in processes such as electrophotography, electrostatic recording and electrostatic printing. A liquid developing method used and a dry developing method using a powder developer are known.
The liquid development method uses a large amount of organic solvent for the developer and is not suitable for general office work due to problems such as solvent vapor diffusion.
In recent years, the dry developing method has become the mainstream because of its ease of handling. However, the dry developing method has a limit in terms of obtaining a high-definition image because the particle size of the powder developer (toner) is as coarse as about 10 μm. On the other hand, in the liquid development method, since the developer particles (hereinafter referred to as toner) are extremely fine compared to the powder toner, it is possible to achieve high image quality, which is a market trend in recent years, and its advantages have been reviewed. There is.

The developer used in the liquid development method (hereinafter referred to as liquid developer) is a suspension of colored fine powder in an electrically insulating organic solvent (carrier liquid) and has a small particle size. Due to the small size, fine line reproducibility is better than that of the dry development method, and a high-contrast image can be obtained, and its characteristics are also obtained in full-color development using four color toners of yellow, magenta, cyan, and black. You can obtain high resolution and high gradation image quality.

As a method for producing a liquid developer, for example, the following method is generally known. Coloring agents such as carbon black and phthalocyanine in liquids with high insulation (10 ⁹ Ωcm or more) and low dielectric constant (3 or less) such as petroleum hydrocarbons, and adjusting the charge of toner particles by adsorbing or coating on them. Toner particles forming resin that contributes to improving the fixing property of images after development, and substances that dissolve or swell in the carrier liquid and increase the dispersion stability of toner particles, and strengthen the charge of toner particles It is prepared by dispersing a stabilizing substance.

In such a liquid developer, the toner particles are extremely fine (1 μm or less), and therefore the dispersion stability is relatively good. However, if the toner is left for a long time, the toner solids will settle in the carrier liquid. If it does, it will solidify and become unusable. In addition, since the particle size is extremely small, the specific surface area increases, and as a result, the amount of the charge-strengthening stabilizer and the dispersion stabilizer having strong hydrophilicity increases, and the obtained image is strongly affected by the operating environment-particularly humidity. Will end up. Further, since the toner particle size is small, the toner mobility is small and it is difficult to speed up the development, and the toner adhesion amount is small, so that there is a problem that the image density is difficult to increase due to insufficient coverage.

Therefore, in place of the liquid developer prepared by dispersing the fine pigment particles in the carrier liquid to melt or swell the resin contributing to the fixing of the toner, a thermoplastic resin for fixing has already been used. Various liquid developers of the type in which fine resin particles in which pigments or dyes are dispersed are suspended in a carrier liquid have been proposed. As a method for producing such a liquid developer, for example, Japanese Patent Publication No. Sho 55-3696,
As disclosed in JP-A-52-125333, JP-A-48-49445 and the like, a carrier liquid containing a toner which is preliminarily miniaturized and contains a pigment or dye and a thermoplastic resin as main components is used as a carrier liquid. There is a way to disperse inside. As a similar one, as described in JP-A-61-36759, a concentrated toner obtained by adding a small amount of a non-aqueous solvent to a thermoplastic resin and a colorant and kneading the mixture with a kneading means such as a ball mill or a high-speed stirrer. Then, there is also a method of dispersing this in a non-aqueous solvent using a disperser. However, the toner particles obtained by such a method have a problem in the particle diameter and the dispersion state of the colorant among the toner particles.

Further, for example, in Japanese Patent Publication No. 2-22946 and Japanese Patent Publication No. 4-13707, a specific resin is dissolved in an aromatic hydrocarbon solvent at a temperature higher than the melting temperature of the resin, and then deposited. A method for producing a liquid developer is disclosed in which the resin is cooled to a temperature below the temperature to form fine particles, and then the solvent is replaced with a highly electrically insulating liquid, and it is described that the colorant can be previously dispersed in the resin. This manufacturing method has an advantage that a toner excellent in agitation, conveyance, and storability can be obtained without causing aggregation and cake formation between the toner particles as described above. However, in this method, after the resin fine particles are generated by precipitation, the solvent must be replaced with a highly electrically insulating liquid in order to be compatible with the liquid development method, and the manufacturing process becomes extremely complicated, and the amount of residual aromatic hydrocarbon solvent remains. There is also a problem in quality control that the developer characteristics are likely to change due to a slight difference in In addition, when actually tracing the manufacturing method, it was found that coarse particles are significantly generated in the knowledge within the range described in the specification, and further, a coarse particle removing step or a crushing step is required, which is sufficient only from the present invention. It is difficult to obtain a liquid developer having performance.

Also, in Japanese Patent Publication No. 4-19547,
There is a description about a manufacturing method similar to the above. in this way,
For example, a mixing or blending vessel equipped with a dispersing medium for dispersing and grinding is charged with at least one resin, a non-polar solvent for dispersing and optionally a colorant. The colorant may be added after the resin and the nonpolar solvent for dispersion are uniform,
A polar solvent may be added if necessary. After the resin is dissolved by heating the container and the contents, each component in the container is sufficiently dispersed while the dispersion medium is irregularly moved in the container. Upon cooling after the completion of dispersion, good toner particles are produced while milling with a dispersion medium to prevent the formation of gel or solid lumps.

In this manufacturing method, since the toner particles do not aggregate or cake when left for a long time as described above, a toner excellent in agitation, transport and storage properties can be obtained. In addition, the manufacturing process has the advantage that it can be performed consistently from the colorant dispersion process to the toner particle generation. However, when actually tracing the examples, the precipitated resin has a strong tendency to cause gelation or solid lumps, and as a result, the generation of coarse particles is suppressed even if it is ground with a dispersion medium. It does not break, and a coarse particle removal process is inevitably required. Furthermore, in this manufacturing method, a polar solvent is added as necessary in order to suppress gelation or lump formation, but the use of a polar solvent is not preferable because it lowers the developability as a liquid developer.

As another method for producing a liquid developer,
For example, there is a method described in JP-A-61-180248. It is insoluble in nonpolar solvents below 40 ° C, and when it exceeds 50 ° C, a thermoplastic resin having the property of being solvated in the nonpolar solvent is once solvated in the nonpolar solvent and then cooled. Is a method for producing a liquid developer by forming finer thermoplastic resin fine particles. This manufacturing method has the following advantages.

1. The toner particles produced by this method have an average particle size of 0.1 to 5 μm and form a plurality of fibers on the surface. This fiber has the following effects. Although the toner particles are relatively coarse as a liquid developer, they settle easily, but due to the presence of fibers, the toner particles do not agglomerate strongly with each other and are easily redispersed by light stirring. b. Excellent reproducibility of fine lines due to the binding force between toner particles during latent image development. 2. In order to solvate the thermoplastic resin with the nonpolar solvent,
The fixing property to the recording medium is significantly improved as compared with the case where only the non-solvating resin is used. 3. Since all manufacturing steps are completed in a non-polar solvent without using a polar solvent, a liquid developer having stable quality can be obtained. 4. The manufacturing process is divided into a process of producing fine resin particles and a process of milling and adding a colorant while forming fibers until the particle size is suitable for the toner. The process can be simplified.

However, even in this manufacturing method,
There are still the following problems. 1. After the resin fine particles are formed, it is necessary to grind while forming fibers until the particle diameter becomes suitable for the toner, and to add a colorant. Among the effects of this step,
It takes an extremely long time to satisfy the effect of grinding to a desired particle size (usually an average particle size of about 3 μm or less in order to realize high image quality, which is a feature of liquid developers). This causes not only the economical problem for reducing the production efficiency per unit time but also the problem of contamination due to abrasion of the grinding (grinding / dispersing) medium in the grinding process which requires a long time. . 2. The resulting toner particle size distribution is very broad,
The coarse particles therein may impair the high definition of the image.

[0013]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made extensive studies to solve the above-mentioned problems, and as a result, produce a liquid developer by precipitating fine resin fine particles by cooling a solvated homogeneous viscous liquid. In the method, by preliminarily dispersing a coloring agent in a high concentration in a part of the resin to produce colored resin fine particles, a liquid developer having a sharp particle size distribution and no coarse particles can be produced economically and stably. The inventors have found that they can do so and have reached the present invention.

[0014]

The present invention provides a thermoplastic resin having a property of being insoluble in a nonpolar solvent below a predetermined temperature and solvating in the nonpolar solvent above a predetermined temperature,
Once solvated in the non-polar solvent and then cooled to form fine thermoplastic resin fine particles, in a method for producing a liquid developer, a coloring agent is previously added to the thermoplastic resin at a high concentration. When dispersed and used in combination with a thermoplastic resin or a composition containing a thermoplastic resin, colored resin fine particles are produced , and the thermoplastic resin is heated by heating.
When cooling from the state of being solvated with the non-polar solvent,
Solvated thermoplastic resin begins to precipitate as fine particles
When the temperature is T ₁ ° C, the temperature of the non-polar solvent during the above cooling
T ₀ is in the temperature range of (T ₁ −10) ° C <T ₀ <(T ₁ +5) ° C.
Control the cooling rate dT / dt of the non-polar solvent within the following range
There is provided a method for producing a liquid developer for developing an electrostatic charge image, the method comprising: -5 ℃ / hour <dT / dt <-0.2 ℃ / hour

The present invention will be described in detail below. First, differences between the manufacturing methods described in Japanese Patent Publication No. 2-22946 and Japanese Patent Publication No. 4-13707 and the manufacturing method described in Japanese Patent Laid-Open No. 61-180248 will be considered. In the former, a resin having a specific structure is dissolved in an aromatic hydrocarbon solvent at a temperature exceeding the melting temperature of the resin, whereas in the latter, the structure of the resin is not particularly limited and heating To solvate with a non-polar solvent. Solvation refers to a phenomenon in which molecules or ions of a solute (here, a resin) in a solution particularly attract some of the solvent molecules adjacent to the solute to form one molecular group.

Here, as a carrier liquid generally used for a liquid developer, a non-polar solvent having a high insulating property and a dielectric constant of about 3 or less is used because of problems such as charge imparting to toner particles and easiness of retaining charges. is necessary. However, such a non-polar solvent usually has extremely poor solubility in a thermoplastic resin used for toner, and it is practically difficult to dissolve even if heated. For this reason, in the former manufacturing method, first, the solvent is once dissolved in an aromatic hydrocarbon solvent having good solubility in the thermoplastic resin, then cooled and solidified to precipitate the resin, and then the solvent is replaced with a nonpolar solvent. It is a complicated process. On the other hand, in the latter case, since the phenomenon of solvation of the resin and the solvent is utilized, it is a major feature that the solvent replacement step is not required. In addition, the formation of solvation significantly changes the characteristics of the resin before solvation, particularly lowers the melting temperature during heating, and improves the fixability.

Here, when the mixture of the resin and the solvent is heated, it is not always easy to strictly distinguish whether the resin is dissolved or solvated in the solvent. One simple idea is that, in the case of dissolution, the resin and solvent do not form one molecular group, so the dissolution start temperature at the time of temperature rise becomes equal to the precipitation start temperature at the time of cooling, but in the case of solvation Sometimes it is not equal. Although the former and the latter have the same effect with respect to the purpose of merely forming resin fine particles, the present invention provides a liquid developer having a sharp particle size distribution and no coarse particles economically and stably, and more specifically, Is to obtain fine particles having a particle size suitable for a toner directly in order to omit the step of grinding or pulverizing the precipitated resin which must be used in any of the above methods. The method described in JP-A-180248 is preferable, in which the resin is solvated with a non-polar solvent by heating and then cooled to precipitate. For the purpose of facilitating solvation, it is possible to add a very small amount of another organic solvent within a range that does not impair the characteristics of the liquid developer.

The non-polar solvent used as the carrier liquid in the present invention is a hydrocarbon solvent having a dielectric constant of 3.0 or less and electrical insulation (volume specific resistance of 10 ⁹ Ωcm or more). A branched-chain aliphatic hydrocarbon is preferable, and it is desirable that the boiling point thereof is in the range of 150 to 220 ° C. in view of handling problems when heating for solvation. Isopar (trade name) manufactured by Exxon Chemical Co., Ltd. is the most common nonpolar solvent having such characteristics.
More specifically, Isopar G, Isopar H, Isopar L and the like are most preferable, but not limited to these. Examples of other solvents include Shellsol A, AB (trade name) manufactured by Shell Co., and Naftesol L, M, H (trade name) manufactured by Nippon Oil Co., Ltd. Can be mentioned.

The thermoplastic resin used in the present invention is not particularly limited as long as it has a property of being solvated by heating with the above carrier liquid. For example, ethyl vinyl acetate copolymer, ethylene copolymer Polymers, acrylic copolymers (ethylene ethyl acrylate, ethylene vinyl acetate, polybutyl methacrylate, polyethyl methacrylate, polymethyl methacrylate, etc.) are suitable. It should be noted that the thermoplastic resin may be only one kind or a mixture of two or more different kinds of resins which are compatible with each other. The thermoplastic resin is insoluble in the nonpolar solvent at a predetermined temperature or lower. The predetermined temperature is about normal room temperature or higher and lower than or equal to the temperature for solvation, but the temperature for solvation varies depending on each thermoplastic resin. If the temperature at which the solvation begins is too high, it will be close to the boiling point of the nonpolar solvent, which is not preferable in terms of handling also from the viewpoint of vapor generation. Therefore, especially 50-100
It is preferably in the range of ° C.

In the method for producing a liquid developer of the present invention, a colorant-dispersed resin is first produced by dispersing a colorant in a high concentration in a part of a thermoplastic resin. Since the colorant in the colorant-dispersed resin is extremely well dispersed by the strong shearing force, it is well distributed among the toner particles even when it is heated and cooled after forming the solvation. The colorant concentration in the colorant-dispersed resin is preferably 30 to 70% by weight. 30% by weight
If it is less than 70% by weight, the energy consumption for producing the colorant-dispersed resin is large and it may take a long time to disperse, which is uneconomical. If it exceeds 70% by weight, the stability of the colorant in the colorant-dispersed resin is high. Is insufficient and reaggregation of the colorant occurs, which is not preferable. Experimentally, especially 40-60% by weight
It has been confirmed that the best results are obtained in the range of.

As a method of dispersing the colorant in the thermoplastic resin, for example, a two-roll mill, a three-roll mill, a pressure kneader, a twin-screw extrusion kneader, or the like is used, and a method of melt kneading and dispersing by shearing force and heat, And, by softening the resin by adding a small amount of a solvent, there is a method of mainly dispersing by shearing force, but for the above purpose, the former usually called a masterbatch is preferable mainly from the viewpoint of dispersion stability, Even in the latter case, the year will be greatly reduced temporarily, so it is necessary to add a dispersant as necessary so that the dispersed colorant does not re-aggregate at that time. As the colorant, pigments or dyes that are commonly used can be used, for example, Hansa Yellow, Disazo Yellow, Quinoline Yellow, Permanent Yellow, Benzidine Orange, Bengala, Fast Red, Resole Red, Permanent Red, Watchyan Red Calcium Salt, Pigments or dyes such as Watchyan red manganese salt, pyrazolone red, lake red C, lake red D, brilliant carmine 3B or 6B, dark blue, phthalocyanine blue, Victoria blue, nigrosine and carbon black can be used.

Next, the above-mentioned colorant-dispersed resin, thermoplastic resin and non-polar solvent are blended at room temperature, and then stirred and mixed while heating, whereby the colorant-dispersed resin and thermoplastic resin are nonpolarized. Solvate in a polar solvent. At this time, this mixture is a slightly viscous and uniform liquid substance. It should be noted here that the resin in this liquid substance is not dissolved in the solvent, so after heating it after it becomes a uniform liquid substance, it may be cooled by mixing conditions (time and shearing force). That is, the property of the resin fine particles of (1) changes greatly. If the resin is simply dissolved, such a difference should not occur, and from this point also, the production method of the present invention is described in Japanese Patent Publication No. 2-22946 and Japanese Patent Publication No. 4-137.
It can be understood that the method is different from the method described in Japanese Patent Publication No. 07. The reason why the thermoplastic resin is used in combination with the above colorant-dispersed resin is to dilute the colorant since the colorant is contained in an ordinary liquid developer in an amount of about 3 to 10% by weight. The thermoplastic resin in which the colorant is dispersed and the thermoplastic resin used in combination with the colorant-dispersed resin may be different types of resins as long as they are compatible with each other.

The following points must be noted as conditions for preparing the non-polar solvent, the colorant-dispersed resin and the thermoplastic resin at room temperature and then stirring and mixing while heating. 1. Thermoplastic resin concentration during solvation: eg 30-50%
It may be better to solvate at higher concentrations of than. When solvating at a high concentration, it becomes a step of diluting with a heated nonpolar solvent and then cooling if necessary, but stirring time after dilution at that time,
Rotational speed is also important. 2. Agitation speed: It may be better to rotate the agitation blade at a high speed. 3. Maximum temperature: The maximum temperature during heating should not be too high from the viewpoint of the particle size of the produced resin fine particles and the economical efficiency. These conditions are specifically, for each thermoplastic resin /
Optimum conditions vary depending on the type of non-polar solvent, so it cannot be specified here. It is necessary to empirically determine manufacturing conditions to some extent.

Next, the uniform viscous liquid of the thermoplastic resin which is solvated with the nonpolar solvent is cooled by heating to deposit colored resin fine particles. At this time, by controlling the cooling rate dT / dt within the following range and specifying the precipitation conditions,
Particles having a very sharp particle size distribution and no coarse particles can be obtained economically and stably. That is, when the temperature at which the thermoplastic resin begins to precipitate as fine particles when the thermoplastic resin is cooled from the state in which the thermoplastic resin is solvated with the nonpolar solvent by heating is T ₁ ° C, the cooling is performed. In the temperature range of (T ₁ −10) ° C. <T ₀ <(T ₁ +5) ° C., the nonpolar solvent temperature T _{0 at} that time is equal to the cooling rate dT / dt of the non-polar solvent of −5 ° C./hour < dT
Control within the range of / dt <-0.2 ° C / hour. At this cooling rate, the resin fine particles that have started to precipitate do not substantially agglomerate at all, and therefore, the shearing force for grinding and atomizing the particles is not required.

Here, the method of measuring dT / dt is as follows.
It is the measured value of the temperature gradient measured by directly inserting a thermometer into the material at regular intervals. The material measured temperature at a certain time ta is Ta ° C., and a time tb after a time Δt from that time.
When the measured material temperature at Tb is dT / dt = (Tb-Ta
) / Δt.

The above-mentioned precipitation starting temperature T ₁ is empirically determined depending on the types of the thermoplastic resin and the nonpolar solvent used. Empirically, it is preferable to make the cooling rate as slow as possible, but if the cooling rate is controlled in the above temperature range, particle formation is not substantially affected in other regions. The precipitation start temperature T ₁ may not always be clearly measured. Therefore, as a guide, by cooling the solvate that was a uniform viscous liquid, it changes to "mashed potato-like" at a certain temperature or lower, and then the volume decreases. Since this "mashed potato-like" state is maintained for approximately 2 to 5 ° C, T ₁ is defined as the first temperature at which the product becomes "mashed potato-like".

Another point to be noted during the production is to effectively stir the solvate during cooling so that the temperature of the solvate becomes uniform and to minimize the shearing force applied to the solvate. May be smaller. If the stirring is insufficient, a temperature distribution occurs in the solvate, uniform and fine resin particles are not generated, and if the shearing force during stirring is large, the precipitated resin particles may aggregate. The problem does not give equally good results. It can be judged that the shear force is excessively applied because when the solvate is cooled at a constant cooling rate, the material temperature of the solvate does not cool at a constant rate due to self-heating due to excessive shear force. As a stirrer for mixing resin and non-polar solvent to form solvation and then depositing resin particles, various stirrers that can be heated / cooled using a normal heat medium can be used, paddle stirrer, turbine stirrer. , A propeller-type stirrer, a spiral-type stirrer, an arm-type stirrer, and the like. Further, the number of stirring blades may be one or plural, and in particular, a method in which each of the plurality of stirring blades revolves around its own axis is preferable because efficient stirring can be performed without applying excessive shearing force.

To the suspension of colored resin fine particles thus produced, a colorant powder is added in order to impart a desired color as in the conventional production method, or a medium stirring mill such as a ball mill, a sand mill or a wet attritor is used. There is no need for a step of fixing the colorant powder to the resin fine particles by treating for a long period of time, or a grinding and crushing step as in various conventionally proposed methods. Actually, when the generated colored resin fine particles are treated for a short time using a medium stirring mill, the average particle diameter is slightly reduced from the initial stage, but this is thought to be mainly for crushing mild aggregates.

The colored resin fine particle suspension thus obtained requires a charge-imparting agent for selective development according to the charge pattern of the electrostatic image. As a result, a liquid developer can be obtained. This charge-giving agent is roughly classified into 2
There are two types. One is a method of coating the surface of toner particles with a substance capable of ionizing or adsorbing ions. Examples of this type include oils and fats such as linseed oil and soybean oil, alkyd resins, halogenated polymers, aromatic polycarboxylic acids, water-soluble dyes containing acidic groups, and oxidative condensation products of aromatic polyamines.

The other is to coexist with a substance that can be exchanged with the toner particles by dissolving it in a carrier liquid, and a metal stone such as cobalt naphthenate, nickel naphthenate and cobalt 2-ethylhexanoate. Kens,
Calcium dodecylbenzene sulfonate, petroleum sulfonate metal salts, sulfonate metal salts such as metal salts of sulfosuccinate, lecithin, polyvinylpyrrolidone resin, polyamide resin, sulfonic acid-containing resin, hydroxybenzoic acid derivative, etc. may be used. it can.

In addition, additional components that may be present in the liquid developer can be added if desired.

[0032]

EXAMPLES The present invention will be described below based on examples.
In the examples, “part” means “part by weight” and “%” means “% by weight”. For image evaluation, a liquid developing and copying machine (Savin870: manufactured by Sabin) using a developer diluted to a nonvolatile content of 1.5%
The printed matter obtained in 1. was used.

Example 1 The following formulation was weighed. Ethylene-methacrylic acid copolymer 100 parts (trade name: Nucrel N1525, manufactured by Mitsui DuPont Polychemical Co., Ltd.) Yellow pigment 100 parts (trade name: Lionol Yellow FG1310, manufactured by Toyo Ink Mfg. Co., Ltd.) Dispersion stabilizer 10 Part This was melt-kneaded with a hot three-roll mill, cooled and solidified, and then crushed into a coarse powder of about 2 mm square. This is designated as colorant dispersion resin A. Next, the following formulation was weighed. Aromatic hydrocarbon-based non-polar solvent 950 g (trade name: Isopar L, manufactured by Exxon Chemical Co., Ltd.) Ethylene-methacrylic acid copolymer 840 g (trade name: Nucrel N1525, manufactured by Mitsui DuPont Polychemical Co., Ltd.) Colorant dispersion Resin A 110g

This was put into a stirrer (trade name: Double Planetary Mixer DP-5, manufactured by Tokushu Kika Kogyo Co., Ltd.) having a jacket for passing a heat medium, and stirred under the following conditions. 1. Temperature rise: Stirring was started with the material at room temperature. When this was heated to a material temperature of 115 ° C. for 1 hour, it became a slightly viscous solvate, and then stirring was continued for another 30 minutes. The rotation speed at this time was set to 6 by the attached rotation speed control scale. 2. Addition of heating solvent: 1050 g of Isopar L heated to 120 ° C. was added thereto, and stirring was continued for another hour. The rotation number at this time was the attached rotation number control scale 6.

3. Cooling: The number of rotations was reduced to 2 and the heating medium in the jacket was cooled to start cooling the material. In the combination of the nonpolar solvent and the resin used in this example, the precipitation start temperature was about 70 ° C, so the material temperature was 75 ° C.
Until about -30 ° C / hour. Material temperature 75 ℃ to 60 ℃
During this period, the cooling rate was −4 ° C./hour. The material temperature became "mashed potato-like" between 70 ℃ and 66 ℃, and then became a viscous substance from 65 ℃ to 61 ℃. After that, when the material temperature was 60 ° C or lower, the cooling rate was again set to -30 ° C / hour. At the material temperature of 59 ° C, a slightly viscous yellow cream-like substance was formed, which did not change until it reached room temperature. The cooling operation was completed when the material temperature reached 40 ° C. The time required for the above cooling was about 6 hours.

After cooling to room temperature, the particle size distribution of the precipitated colored resin fine particles is measured by a centrifugal sedimentation type particle size distribution measuring instrument (trade name:
The SA-CP3L type, manufactured by Shimadzu Corporation, had an average particle size of 2.0 μ, and contained no particles of 5 μ or more and 6% or 8 μ or more. The colored resin fine particle suspension was diluted with Isopar L to a nonvolatile content of 1.5% to obtain a developer.
When lecithin was added at a ratio of 1.0 part to 1000 parts of the developing solution and an image test was conducted, a good image with a reflection density (reflection densitometer, Macbeth RD-918 used) of 1.0 or more and no background stain was obtained. It was

Example 2 The following formulation was weighed. Ethylene-methacrylic acid copolymer 40.0 parts (Brand name: Nucrel 010, manufactured by DuPont) Red pigment 38.9 parts (Brand name: Fines Red F2B, manufactured by Toyo Ink Mfg. Co., Ltd.) Yellow pigment 2.0 Part (Brand name: Lionol Yellow FG1310, manufactured by Toyo Ink Mfg. Co., Ltd.) Dispersion stabilizer 0.5 part This is melted and kneaded with a hot three-roll mill, cooled and solidified, and then crushed with a pulverizer to about 2 mm square It was made into a coarse powder. This is designated as colorant dispersion resin B. Next, the following formulation was weighed. Isopar L 750 g Ethylene-methacrylic acid copolymer 675 g (trade name: Nucrel 010, manufactured by DuPont) Colored resin powder B 75 g

This was put into the same stirrer as in Example 1,
The mixture was stirred under the following conditions. 1. Temperature rise: Stirring was started with the material at room temperature. When this was heated to a material temperature of 130 ° C. for 2 hours, it became a colorless, transparent, and slightly viscous solvate, and the stirring was continued for another 1 hour. The rotation speed at this time was set to 6 by the attached rotation speed control scale. 2. Addition of heating solvent: 1500 g of Isopar L heated to 130 ° C. was added thereto, and stirring was continued for another hour. The rotation number at this time was the attached rotation number control scale 6. 3. Cooling: The resin fine particles were deposited by cooling in the same manner as in Example 1 below. The time required for the above cooling was about 7 hours.

After cooling to room temperature, the particle size distribution of the precipitated colored resin fine particles was measured in the same manner as in Example 1, and it was found that the average particle diameter was 1.2 μm and particles of 5 μm or more were not contained.
This was diluted with Isopar L to a nonvolatile content of 1.5% to obtain a developer. When lecithin was added at a ratio of 1.0 part to 1000 parts of the developing solution and an image test was conducted, a good image having a reflection density (reflection densitometer, Macbeth RD-918 used) of 1.3 or more and no background stain was obtained. It was

[Embodiment 3] Material temperature 75 in Embodiment 1
When the cooling rate from ℃ to 60 ℃ was changed as shown in Table 1, the average particle size and coarse particles (20
The mesh sieve residue%) was as shown in Table 1. Since the average particle diameter of these colored resin fine particles is too large as they are, a suspension of the colorant-dispersed resin is placed in a 5 liter attritor using 3/16 inch stainless beads at room temperature for 240 r.
processed by pm. By treating for 7 hours in Example 3-1 and for 3 hours in Example 3-2, the average particle diameter of the resin fine particles was 3 μm.
It became the following, and substantially no particles of 8 μ or more were contained. An image test was conducted using this as a developer in the same manner as in Example 1. As a result, a good image having a reflection density of 1.3 or more and having no background stain was obtained.

[0041]

[Table 1]

Comparative Example The following formulation was weighed. Isopar L 750 g Ethylene-methacrylic acid copolymer 750 g (trade name: Nucrel 010, manufactured by DuPont) This was stirred, heated and cooled in the same manner as in Example 2 to precipitate fine resin particles. After cooling to room temperature, the particle size distribution of the precipitated resin fine particles was measured in the same manner as in Example 1 to find that the average particle size was 0.9 μm and particles of 5 μm or more were not included. However, since the resin fine particles are not colored, they cannot be used as they are as a liquid developer, and further, weighing and mixing of the colorant are required, which makes the operation extremely complicated, which is not preferable.

[0043]

According to the present invention, a color developer is dispersed in a high concentration in a part of a thermoplastic resin in advance to directly produce fine colored resin particles, whereby a liquid developer having a sharp particle size distribution and no coarse particles. Can be obtained economically and stably.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koji Miyabayashi 2-13-3 Kyobashi, Chuo-ku, Tokyo Toyo Inki Manufacturing Co., Ltd. (56) Reference JP-A-58-152258 (JP, A) JP 58-129438 (JP, A) JP-A-48-82828 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/13

Claims (4)

(57) [Claims] 1. A thermoplastic resin which is insoluble in a non-polar solvent at a predetermined temperature or lower, and has a property of being solvated in the non-polar solvent at a predetermined temperature or higher, is once solvated in the non-polar solvent, A method of producing a liquid developer by forming fine thermoplastic resin fine particles by cooling, in which a coloring agent is dispersed in a high concentration in advance in the thermoplastic resin, and a thermoplastic resin or a thermoplastic resin is included. When used in combination with the composition, to produce colored resin fine particles, and when the thermoplastic resin is cooled from the state of being solvated with the nonpolar solvent by heating, the solvated thermoplastic resin is When the temperature at which precipitation of fine particles begins is T ₁ ° C, the nonpolar solvent temperature T ₀ during the cooling is (T ₁ -10) ° C <T ₀ <(T ₁
Cooling rate dT of the non-polar solvent in the temperature range of +5) ° C
A method for producing a liquid developer for developing an electrostatic charge image, comprising controlling / dt within the following range. -5 ℃ / hour <dT / dt <-0.2 ℃ / hour 2. The method for producing a liquid developer for developing an electrostatic charge image according to claim 1, wherein the solvated thermoplastic resin is cooled while being stirred without being crushed. 3. The method for producing a liquid developer for developing an electrostatic charge image according to claim 1, wherein particles having a particle size of 8 μm or more are substantially absent. 4. The method for producing a liquid developer for developing an electrostatic charge image according to claim 1, wherein a colorant is previously dispersed in the thermoplastic resin at a high concentration and then pulverized.