JP3267716B2 - Liquid developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developer used for an electrophotographic apparatus and ionography.

[0002]

2. Description of the Related Art Electrophotographic developers are classified into a powder developer using a powder toner and a liquid developer in which toner particles are dispersed in a liquid. At present, powder developers are widely used in general, but due to recent demands for higher image quality of printed matter, liquids that can achieve full color and high image quality by using toner particles with a small particle diameter Developers are attracting attention. As a configuration of the liquid developer, basically, a colorant, a resin, a charge control agent,
Generally, a carrier liquid that is a solvent having a high insulating property is used. The colorant, of course, determines the color of the printed matter. In addition, a colorant that has an electric charge and contributes to electrophoresis has been proposed. The role of the resin is to act as a binder between the colorant and the paper or OHP sheet to be printed, or to hold the charge for the toner particles to perform electrophoresis. The role of the charge control agent is to adjust the charge of the toner particles, to give the toner particles dispersion stability, and the like.

As a method for producing a liquid developer, a method of polymerization, a method of pulverizing and dispersing a resin, a method of mixing a resin and a colorant, a method of depositing particles, and the like have been invented. To create toner particles and add a charge control agent. There are two types of charge control agents, one for positive charge and the other for negative charge, and various inventions have been invented for each of them. In particular, many charge control agents for negative charge have been invented, and the demand for such charge control agents has been known. As typical negative charge control agents, surfactants such as lecithin, linseed oil and metal soap are known, and are used alone or in combination. Among them, there are many inventions of liquid developers using a charge controlling agent containing soybean lecithin, but none of them specifically considers a component of lecithin.

However, the stability of the liquid developer using any of the charge control agents has been improved over time. However, when an image is output, the initial image is good, but the image is continuously improved. If output is continued, there is a disadvantage that the image quality gradually decreases. This is because the electric conductivity, which is one index indicating the characteristics of the developer, changes, and as a result, the electrophoretic force of the toner particles is affected. Since the liquid developer used in a high-speed output machine must catch up with the process speed, the electrophoresis speed of the toner particles must be sufficiently high.
The change in electrical conductivity is due to the poor chemical stability and humidity resistance of the surfactant used as the charge control agent. Further, during the development / transfer process in the electrophotographic apparatus, the developer is exposed to an electric field, thereby depleting some components of the charge control agent contained in the developer.

However, this has not been a serious problem in low-speed electrophotographic apparatuses. The reason is that the above-mentioned depleted component is restored with the passage of time, and this is a problem for the first time in a high-speed output machine that does not have a sufficient restoration time. Further, the electrophotographic apparatus is rarely used in a place where the temperature and humidity are constant.
Therefore, due to the hydrophilicity of the charge control agent added to the liquid developer, as a result of taking in atmospheric moisture into the developer, the electric conductivity, which is one index indicating the characteristics of the liquid developer, is reduced. And image quality becomes unstable. Against this background, in addition to adjusting the charge of toner particles and adding dispersion stability to toner particles, which have been the conventional roles of charge control agents, humidity resistance, aging stability, and stability against electric field loads are added. Have been invented and used.

[0006] For example, in the invention of USP 4,897,332,
It is disclosed that when an alkylated polyvinylpyrrolidone or polyvinylpyrrolidone and a surfactant such as lecithin are mixed in a highly insulating solvent and used as a charge control agent, the stability to an electric field load is improved.
Further, the invention of US Pat. No. 5,047,306 discloses that when a polymer in which polyvinylpyrrolidone is a typical example and a surfactant such as lecithin and a basic petroleum sulfonate are used as a charge control agent, the moisture resistance of the developer is reduced. It is disclosed that the performance is improved.

[0007]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the content of the insulating liquid, toner particles, and phosphatidylethanolamine or phosphatidylserine is 40 to 90% by weight. The present inventors have found that a liquid developer containing lecithin has excellent moisture resistance and resistance to electric field load, stably maintains developing performance over a long period of time, and has high toner mobility. The liquid developer of the present invention exerts its effects particularly in a high-speed output electrophotographic apparatus.

[0008]

That is, the present invention relates to a liquid developer containing an insulating liquid, toner particles and a charge control agent, wherein the charge control agent has a phosphatidylethanolamine content of 40 to 90% by weight. A liquid developer comprising lecithin. The present invention also provides a liquid developer in which the charge control agent contains lecithin having a phosphatidylserine content of 40 to 90% by weight.

As the insulating liquid, an electric resistivity of 10 ⁹ Ωc
Use a solvent having a dielectric constant of m or more and a dielectric constant of 3 or less, for example, Isopar H, G, L, M manufactured by Exxon Chemical Co., Ltd. One of the materials constituting the toner particles, dyes and pigments used as a coloring material are conventionally known various materials, such as carbon black, phthalocyanine blue, alkali blue,
Azo pigments can be used without any problem. Further, as a resin that is another material constituting the toner particles, for example,
Acrylic polyacrylates, polymethacrylates, ethylene-based ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and the like can be used, but are not limited thereto.

As the constituent material of the charge control agent, lecithin having a phosphatidylethanolamine or phosphatidylserine content of 40 to 90% by weight is used. Phosphatidylethanolamine and phosphatidylserine mainly act on the charging of toner particles, and when the content of phosphatidylethanolamine or phosphatidylserine is less than 40% by weight, the stability when exposed to an electric field is deteriorated. If the amount is more than 10% by weight, the electric conductivity of the obtained developer is too low. Conventionally, lecithin purified from soybean has been used. The typical lipid composition of soybeans is 18-21% phosphatidylcholine, 12-16% phosphatidylethanolamine, and 11% phosphatidylinositol.
1414%, phosphatidic acid about 2%, phosphatidylserine 3-4%. Purified and marketed as lecithin, the lipid composition is 25-35% phosphatidylcholine and 23-33% phosphatidylethanolamine.
%, Phosphatidylinositol is 10-20%, and phosphatidic acid is 4-12%.

[0011] Petroleum sulfonate can be added to the charge control agent in order to further improve the humidity resistance. As the petroleum sulfonate, basic calcium petronate and basic barium petronate manufactured by Witco are preferably used. Further, an alkyl allyl sulfonate can be further added to the charge control agent. Alkyl allyl sulfonate is soluble in a non-polar solvent. For example, metal salts such as sodium salt and calcium salt of alkylbenzenesulfonic acid having 6 to 20 carbon atoms and organic salts are used.

The charge control agent containing lecithin having a phosphatidylethanolamine or phosphatidylserine content of 40 to 90% by weight is added in an amount of 0.01 to 10 g per 100 g of a liquid developer having a toner particle content of 0.1 to 5.5% by weight. As a result, a good electric conductivity of the liquid developer and an appropriate charging state of the toner particles can be obtained, thereby stabilizing the electrophoretic force of the toner particles. A stable image output can be obtained. In addition, the charge adjusting agent can produce a developer of each color with a substantially constant addition amount without being affected by the color of the coloring agent.

[0013]

The present invention will be described below in further detail with reference to examples. In the examples, “part” indicates “part by weight” and “%” indicates “% by weight”. Example 1 A mixture consisting of 15 parts of lecithin: 15 parts of Isopar H (manufactured by Exxon) containing 40% of phosphatidylethanolamine was prepared and used as a charge control agent. (Example 2) Lecithin: A mixture consisting of 15 parts of Isopar H (manufactured by Exxon) 85 parts containing 80% of phosphatidylserine was used as a charge control agent.

Example 3 Lecithin: 10 parts containing 60% phosphatidylethanolamine Basic barium petronate (manufactured by Witco) 5 parts Isopar H (manufactured by Exxon) 85 parts was prepared as a charge control agent. And (Example 4) Lecithin: 10 parts containing 40% of phosphatidylserine Basic calcium petronate (manufactured by Witco) 5 parts Isopar H (manufactured by Exxon) A mixture consisting of 85 parts was prepared and used as a charge control agent.

(Example 5) Lecithin: 10 parts containing 60% of phosphatidylethanolamine Basic barium petronate (manufactured by Witco) 3 parts Sodium salt of laurylbenzenesulfonic acid 2 parts Isopar H (manufactured by Exxon) 85 parts Was prepared and used as a charge control agent. (Example 6) Lecithin: containing 80% of phosphatidylserine 10 parts Basic barium petronate (manufactured by Witco) 3 parts Sodium salt of laurylbenzenesulfonic acid 2 parts Isopar H (manufactured by Exxon) 85 parts A mixture was prepared. And used as a charge control agent.

Comparative Example 1 A mixture consisting of 15 parts of lecithin: Basis LP-21 (manufactured by Nisshin Oil Co., Ltd.) and 85 parts of Isopar H (manufactured by Exxon) was prepared as a charge control agent. (Comparative Example 2) Lecithin: Basis LP-21 (manufactured by Nisshin Oil Co., Ltd.) 15 parts Alkylated polyvinylpyrrolidone: ANTARON V-216 5 parts (manufactured by ISP) Isopar H (manufactured by Exxon) 80 parts It was prepared and used as a charge control agent.

(Comparative Example 3) Lecithin: Basis LP-21 (manufactured by Nisshin Oil Co., Ltd.) 10 parts Basic barium petronate (manufactured by Witco) 5 parts N-vinyl-2-pyrrolidone (manufactured by ISP) 5 parts 1 part of lauroyl peroxide (manufactured by NOF CORPORATION), 80 parts of Isopar H (manufactured by Exxon) were mixed and heated at 100 ° C. for 10 hours to convert the monomer into polyvinylpyrrolidone, which was used as a charge control agent.

(Toner Liquid Example 1) A mixture composed of 20 parts of ethylene-methacrylic acid copolymer, 1 part of carbon black, and 80 parts of Isopar G (manufactured by Exxon) was put in an attritor and kneaded for 30 hours to prepare a concentrated toner liquid. . This was diluted with Isopar G to a nonvolatile content of 2% to obtain a toner liquid. (Toner liquid example 2) Ethylene-methacrylic acid copolymer 20 parts Pigment Lionol Blue FG7351 (manufactured by Toyo Ink Mfg. Co., Ltd.) 1 part Isopar G (manufactured by Exxon) 80 parts A mixture consisting of 80 parts was kneaded in the same manner as in Example 1. , To give a toner liquid.

(Toner liquid example 3) Ethylene-methacrylic acid copolymer 20 parts Pigment Lionol Yellow FG1310 (Toyo Ink Mfg. Co., Ltd.) 1 part Isopar G (Exxon Co., Ltd.) 80 parts Similarly, the mixture was kneaded and diluted to obtain a toner liquid. (Toner liquid example 4) Ethylene-acrylic acid copolymer 20 parts Pigment Finesthread F2B (manufactured by Toyo Ink Mfg. Co., Ltd.) 1 part Isopar G (manufactured by Exxon) A mixture consisting of 80 parts was kneaded in the same manner as in Example 1. , To give a toner liquid.

(Evaluation 1) 10 g of each of the charge control agents of Examples 1 to 6 and Comparative Examples 1 to 3 was added to each of the combinations shown in Table 1 to 1000 g of the 2% toner liquid prepared in Examples 1 to 4. The developer was used as a developer, and an image output test was performed on plain paper using a copying machine for liquid development: SAVIN870 (manufactured by SAVIN). Image output was performed 10 times with 1000 cycles continuous output, electrical characteristics check immediately after that, and 2 hours left as one cycle.
The solid image density of the last image of each cycle was measured with a reflection densitometer: Macbeth RZ-918 (manufactured by Macbeth). In addition, the measuring method of the electric characteristics is as follows.
Approximately 1 g of the sample was placed between the counter electrodes, and a voltage of 1,500 V DC was applied, and the current flowing at that time was measured. The measured value before image output was set as an initial value, and expressed as a percentage of the initial value. Table 1 shows the results.

[0021]

[Table 1]

(Evaluation 2) In the same manner as in Evaluation 1, a developer was prepared and an image output test was performed. Image output is 10000
The electrical characteristics before and after the continuous sheet output and the image density of the solid portion of the image were measured in the same manner as in Evaluation 1. Table 2 shows the results.
Furthermore, to evaluate the stability over time,
The developer was left at room temperature for 50 days, several images were output, and the image density and the electrical characteristics of the developer were measured in the same manner.

[0023]

[Table 2]

(Evaluation 3) 10 g of each of the charge control agents of Examples 1, 3, and 5 and Comparative Examples 1 and 3 were added to 1000 g of the 2% toner solution prepared in Example 1 of the toner solution to obtain test samples. . Each of these test samples was made in duplicate and 25
A liquid development copier: SAVIN870 (manufactured by SAVIN) performs an image output test on 2,000 sheets of plain paper in an environment of ℃ / 50% RH and 25 ℃ / 90% RH, and visually checks the state of the image. The image density was measured with a reflection densitometer: Macbeth RZ-918 (manufactured by Macbeth). Table 3 shows the results.

[0025]

[Table 3]

As shown in Table 1, when the standing time is provided, the developer recovers, and there is no significant difference between the present invention and the comparative example. This evaluation method simulates a conventional low-speed copier or printer, and it can be seen that this type of evaluation does not cause a serious problem. However, as shown in Table 2, in the simulation of the high-speed machine, that is, when the image is continuously output until the toner particles in the developer are depleted to the extent that replenishment is required, the effect of the present invention is clearly exhibited. Was. Among them, the liquid developer containing a charge control agent to which petroleum sulfonate and alkyl allyl sulfonate are added has particularly excellent performance. In addition, from the storage test of the developer for 50 days, the effectiveness of the present invention also became apparent with respect to the stability over time. Further, as shown in Table 3, the liquid developer containing a charge adjusting agent to which petroleum sulfonate is added has excellent stability against environmental humidity.

[0027]

The liquid developer of the present invention can maintain a stable image output state in a high-speed copier or printer in the case of continuous output, when left for a long period of time, or even in a high environmental humidity condition. Also, a high image density is maintained.

Continuation of front page (56) References JP-A-4-229876 (JP, A) JP-A-4-223479 (JP, A) JP-A-53-109633 (JP, A) JP-A-57-210345 (JP) JP-A-61-278868 (JP, A) JP-A-61-162059 (JP, A) JP-A-57-139753 (JP, A) JP-A-57-90643 (JP, A) 62-266565 (JP, A) JP-A-63-25656 (JP, A) JP-A-63-168662 (JP, A) JP-A-57-90643 (JP, A) JP-A-48-79640 (JP, A A) JP-A-46-7385 (JP, A) JP-B-44-13440 (JP, B1) JP-B-43-21798 (JP, B1) US Patent 4,893,332 (US, A) US Patent 5,047,306 (US, A) ) International Publication No. WO 92/14191 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/12

Claims (5)

(57) [Claims] 1. A liquid developer comprising an insulating liquid, toner particles and a charge control agent, wherein the charge control agent contains lecithin having a phosphotidylethanolamine content of 40 to 90% by weight. Liquid developer. 2. A liquid developer comprising an insulating liquid, toner particles and a charge control agent, wherein the charge control agent contains lecithin having a phosphotidylserine content of 40 to 90% by weight. Liquid developer. 3. The liquid developer according to claim 1, wherein the charge control agent further contains petroleum sulfonate. 4. The liquid developer according to claim 3, wherein the charge control agent further contains an alkyl allyl sulfonate. 5. The liquid developer according to claim 3, wherein the petroleum sulfonate is basic barium petronate or basic calcium petronate.