JPH06208256A - Liquid developer - Google Patents

Abstract

PURPOSE:To provide a liq. developer used in an electrophotographic device and ionography, dspecially a liq. developer effective as a color liq. developer for a high-speed output machine. CONSTITUTION:This liq. developer contains an insulating liq., toner particles and an electric charge regulating agent contg. lecithin or zirconium octate, petroleum sulfonate and alkylated polyvinylpyrro-lidone having 4,000-12,000 average mol.wt. The liq. developer maintains a stable image output state and can maintain high image density in the case of continuous development in a high-speed copying machine or printer, in the case where this liq. developer is allowed to stand over a long period of time and even under the condition of high environmental humidity.

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 in electrophotographic devices and ionography, and more particularly to a liquid developer effective as a color liquid developer for high speed output machines.

[0002]

2. Description of the Related Art Electrophotographic developers can be classified into a powder developer that uses powder toner and a liquid developer in which toner particles are dispersed in a liquid. Currently, powder developers are widely used, but due to the recent demand for higher image quality in printed matter, the use of toner particles with a small particle size makes it possible to achieve full color and high image quality. Developers are attracting attention. The composition of the liquid developer is basically a colorant, a resin, a charge control agent,
It is generally composed of a carrier liquid which is a highly insulating solvent. The colorant, of course, determines the color of the printed matter, but in addition, a colorant that has an electric charge and contributes to electrophoresis has been proposed. The role of the resin is to serve as a binder between the colorant and the printing paper, OHP sheet, or the like, and to retain the electric charge for the toner particles to electrophorese. The role of the charge adjusting 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 by polymerization, a method of crushing and dispersing a resin, a method of mixing a resin and a colorant, a method of precipitating particles, and the like have been invented, and any of these methods can be used. Toner particles are prepared in and a charge control agent is added. There are charge control agents for positive charging and those for negative charging, and various inventions have been made for each of them, but there are many inventions of charge control agents for negative charging in particular, and it is known that the demand thereof is great. Surfactants such as lecithin, linseed oil, and metal soap are known as typical negative charge control agents, and they are used alone or in combination.

However, although the liquid developer using any of the charge control agents is improving in stability over time, when the image is output, the initial image is good, but the image is continuously formed. If the output is continued, there is a drawback that the image quality gradually deteriorates. This is because the electric conductivity, which is one index showing the characteristics of the developer, changes, and as a result, the electrophoretic force of the toner particles is affected. Liquid developers used in high speed output machines must keep up with the speed of the process and therefore the electrophoretic velocity of the toner particles must be fast enough.
The change in electric conductivity is due to the poor chemical stability and humidity resistance of the surfactant used as the charge control agent. Furthermore, during the development / transfer process in the electrophotographic apparatus, the developer is exposed to an electric field, whereby some components of the charge control agent contained in the developer are depleted.

However, this has not been a major problem in low speed electrophotographic devices. The reason is that the above-mentioned depleted component is restored with the passage of time, and such a high-speed output machine with no margin of restoration time becomes a problem for the first time. Further, the electrophotographic apparatus is generally 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, the water content in the atmosphere is taken into the developer, and as a result, the electric conductivity, which is one index showing the characteristics of the liquid developer, is Change and the image quality becomes unstable. Against this background, in addition to the charge control of toner particles and the addition of dispersion stability to toner particles, which were the conventional roles of charge control agents, humidity resistance, stability over time, and stability against electric field loads Invented and used are charge control agents having a.

For example, in the invention of USP 4,897,332,
It has been disclosed that when 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 against an electric field load is improved.
Further, in the invention of USP 5,047,306, when a polymer obtained by binding a surfactant such as lecithin and a basic petroleum sulfonate to a polymer typified by polyvinylpyrrolidone is used as a charge control agent, the moisture resistance of the developer is reduced. It is disclosed that the property is improved.

[0007]

DISCLOSURE OF THE INVENTION As a result of intensive studies to solve the above problems, the present inventors have found that an insulating liquid, toner particles, lecithin or zirconium octate, petroleum sulfonate, and an average molecular weight of 4000 to 12000. A liquid developer containing a charge control agent containing alkylated polyvinylpyrrolidone is excellent in humidity resistance and resistance to electric field load,
The present invention has been completed by finding that the developing performance is stably maintained for a long period of time and the toner has a high mobility. The liquid developer of the present invention exhibits its effect especially in a high-speed output electrophotographic apparatus.

[0008]

That is, the present invention provides a liquid developer containing an insulating liquid, toner particles, and a charge control agent, wherein the charge control agent is lecithin, petroleum sulfonate, and an alkyl having an average molecular weight of 4000 to 12000. Provided is a liquid developer containing polyvinylpyrrolidone fluoride. The present invention also provides a liquid developer in which the charge control agent contains zirconium octate, petroleum sulfonate, and alkylated polyvinylpyrrolidone having an average molecular weight of 4000 to 12000.

The insulating liquid has an electric resistivity of 10 ⁹ Ωc.
A solvent having a m or more and a dielectric constant of 3 or less, for example, Isopar H, G, L, M manufactured by Exxon Chemical Co., Ltd. is used. Dyes and pigments which are one of the materials constituting the toner particles and used as a coloring material are various conventionally known ones, such as carbon black, phthalocyanine blue, alkali blue,
Azo pigments can be used without any problem. Further, as the resin which is another material forming the toner particles, for example,
Acrylic polyacrylic acid ester, polymethacrylic acid ester, ethylene-based ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer and the like can be used, but not limited thereto.

Lecithin and zirconium octate, which are the constituent materials of the charge control agent, contribute to the charging and transferability of the toner particles. As lecithin, those purified from soybean are generally used. As zirconium octate, any commercially available one can be used without limitation. As the petroleum sulfonate, basic calcium petronate and basic barium petronate manufactured by Witco Co. are preferably used because they further improve the humidity resistance. As an alkylated polyvinylpyrrolidone having an average molecular weight of 4000 to 12000, ANTAR manufactured by ISP
ON V-216 and V-220 are typical examples, which contribute to the stability of the developer when exposed to an electric field. Average molecular weight is
If it is less than 4000, the electrical resistance will not be fully exhibited, and 120
If it exceeds 00, the dispersion in the insulating liquid becomes poor.

The charge control agent containing lecithin or zirconium octate, petroleum sulfonate, and alkylated polyvinylpyrrolidone having an average molecular weight of 4000 to 12000 is 0.01 to 10 g per 100 g of liquid developer having a toner particle content of 0.1 to 5.5% by weight. By adding it, good electric conductivity of the liquid developer and appropriate charge state of the toner particles can be obtained, which stabilizes the electrophoretic force of the toner particles, so that the liquid developer can be used for high-speed electrophotographic apparatus. Then, stable image output can be obtained for a long period of time. Further, it is possible to produce the developer of each color with an almost constant addition amount of the charge control agent without being influenced by the color of the colorant.

[0012]

The present invention will be described in more detail based on the following examples. In the examples, "part" means "part by weight" and "%" means "% by weight". (Example 1) Lecithin: Basis LP-21 (manufactured by Nisshin Oil Co., Ltd.) 10 g Basic barium petronate (manufactured by Witco) 5 g Alkylated polyvinylpyrrolidone: ANTARON V-216 5 g (manufactured by ISP) Isopar H ( (Exxon) 80 g of a mixture was prepared and used as a charge control agent. (Example 2) Lecithin: Basis LP-21 (manufactured by Nisshin Oil Co., Ltd.) 10 g Basic calcium petronate (manufactured by Witco) 5 g Alkylated polyvinylpyrrolidone: ANTARON V-216 5 g (manufactured by ISP) Isopar H ( (Exxon) 80 g of a mixture was prepared and used as a charge control agent.

Example 3 Lecithin: Basis LP-21 (manufactured by Nisshin Oil Co., Ltd.) 10 g Basic barium petronate (manufactured by Witco) 5 g Alkylated polyvinylpyrrolidone: ANTARON V-220 5 g (manufactured by ISP) A mixture of 80 g of Isopar H (manufactured by Exxon) was prepared and used as a charge control agent. (Example 4) Lecithin: Basis LP-21 (manufactured by Nisshin Oil Co., Ltd.) 10 g Basic calcium petronate (manufactured by Witco) 5 g Alkylated polyvinylpyrrolidone: ANTARON V-220 5 g (manufactured by ISP) Isopar H (manufactured by ISP) (Exxon) 80 g of a mixture was prepared and used as a charge control agent.

Example 5 Zirconium Octate (manufactured by Nippon Kagaku Sangyo Co., Ltd.) 10 g Basic barium petronate (manufactured by Witco) 5 g Alkylated polyvinylpyrrolidone: ANTARON V-216 5 g (manufactured by ISP) Isopar H ( (Exxon) 80 g of a mixture was prepared and used as a charge control agent. (Example 6) Zirconium octoate (manufactured by Nippon Kagaku Sangyo Co., Ltd.) 10 g Basic calcium petronate (manufactured by Witco) 5 g Alkylated polyvinylpyrrolidone: ANTARON V-220 5 g (manufactured by ISP) Isopar H (manufactured by Exxon) ) A mixture of 80 g was prepared as a charge control agent.

Comparative Example 1 A mixture of zirconium octoate (manufactured by Nippon Kagaku Sangyo Co., Ltd.) 20 g Isopar H (manufactured by Exxon) 80 g was prepared as a charge control agent. (Comparative Example 2) Lecithin: Basis LP-21 (manufactured by Nisshin Oil Co., Ltd.) 15 g Alkylated polyvinylpyrrolidone: ANTARON V-216 5 g (manufactured by ISP Co.) Isopar H (manufactured by Exxon Co.) 80 g A mixture was prepared. , As a charge control agent.

Comparative Example 3 Lecithin: Basis LP-21 (manufactured by Nisshin Oil Co., Ltd.) 10 g Basic barium petronate (manufactured by Witco) 5 g N-vinyl-2-pyrrolidone (manufactured by ISP) 5 g Lauroyl peroxide (Nippon Yushi-Seiyaku Co., Ltd.) 1 g Isopar H (manufactured by Exxon Co.) 80 g was mixed and heated at 100 ° C. for 10 hours to make polyvinylpyrrolidone as a monomer to obtain a charge control agent.

(Toner Liquid Example 1) Ethylene-methacrylic acid copolymer 20 parts Carbon black 1 part Isopar G (manufactured by Exxon) A mixture of 80 parts was placed 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 Rionol Blue FG7351 (manufactured by Toyo Ink Mfg. Co., Ltd.) 1 part Isopar G (manufactured by Exxon) 80 parts A mixture was kneaded in the same manner as in Example 1. And diluted to obtain a toner liquid.

(Toner Liquid Example 3) Ethylene-methacrylic acid copolymer 20 parts Pigment Lionol Yellow FG1310 (manufactured by Toyo Ink Mfg. Co., Ltd.) 1 part Isopar G (manufactured by Exxon Co.) 80 parts A mixture was used as in Example 1. Similarly, it was kneaded and diluted to obtain a toner liquid. (Toner Liquid Example 4) Ethylene-acrylic acid copolymer 20 parts Pigment Fines Red F2B (manufactured by Toyo Ink Mfg. Co., Ltd.) 1 part Isopar G (manufactured by Exxon) 80 parts A mixture was kneaded in the same manner as in Example 1. And diluted to obtain 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 taken and added to 1000 g of the 2% toner liquids prepared in Toner Liquid Examples 1 to 4 in the combinations shown in Table 1. As a developer, a liquid copying machine: SAVIN870 (manufactured by SAVIN) was used to perform an image output test on plain paper. For image output, 1000 sheets are continuously output, electrical characteristics immediately after that are checked, and left for 2 hours as 1 cycle.
The image density of the solid part of the last image of each cycle was measured by a reflection densitometer: Macbeth RZ-918 (manufactured by Macbeth Co.). In addition, the measuring method of the electrical characteristics is as follows: distance between electrodes is 2 mm
About 1 g of the sample was put between the counter electrodes of, and a voltage of DC1500V was applied, and the current value flowing at that time was measured. The measured value before the image was displayed was used as the initial value and expressed as a percentage. The results are shown in Table 1.

[0020]

[Table 1]

(Evaluation 2) In the same manner as in Evaluation 1, a developer was prepared and an image forming test was conducted. Image output is 10000
The electrical characteristics before and after the continuous output of one sheet and the image density of the solid portion of the image were measured in the same manner as in Evaluation 1. The results are shown in Table 2.
Furthermore, in order to evaluate the stability over time, the
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.

[0022]

[Table 2]

(Evaluation 3) The charge control agents of Examples 1, 3 and 5 and Comparative Examples 1 and 3 were added to 10 g of each and 1000 g of the 2% toner liquid prepared in Toner Liquid Example 1 to prepare test samples. . Make two of each of these test samples and
Under the environment of ℃ / 50% RH and 25 ℃ / 90% RH, copy machine for liquid development: SAVIN870 (manufactured by SAVIN Co., Ltd.) was used to test 2000 images on plain paper, and the image condition was visually checked. The image density was measured with a reflection densitometer: Macbeth RZ-918 (manufactured by Macbeth Co.). The results are shown in Table 3.

[0024]

[Table 3]

As shown in Table 1, the recovery of the developer was observed when the standing time was provided, and no significant difference was observed between the present invention and the comparative example. This evaluation method is a simulation of a conventional low-speed copier or printer, and it can be seen that it does not pose a big problem in that category. However, as shown in Table 2, in the simulation of the high-speed machine, that is, in the case where the toner particles in the developer are continuously output until the toner particles are exhausted to the extent that replenishment is required, the effect of the present invention is clearly exhibited. It was Further, from the storage test of the developer for 50 days, the effectiveness of the present invention was clarified with respect to the temporal stability. Further, as shown in Table 3, the liquid developer of the present invention has excellent stability against environmental humidity.

[0026]

INDUSTRIAL APPLICABILITY The liquid developer of the present invention maintains a stable image output state in a high-speed copying machine or printer in the case of continuous output, in the case of being left for a long period of time, and even under the condition of high environmental humidity. It also maintains high image density.

Claims (2)

[Claims] 1. A liquid developer containing an insulating liquid, toner particles, and a charge control agent, wherein the charge control agent comprises lecithin, petroleum sulfonate, and an alkylated polyvinylpyrrolidone having an average molecular weight of 4000 to 12000. Liquid developer to do. 2. A liquid developer containing an insulating liquid, toner particles and a charge control agent, wherein the charge control agent is zirconium octate, petroleum sulfonate and an average molecular weight of 40.
A liquid developer comprising 00 to 12000 alkylated polyvinylpyrrolidone.