JPS6257989B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an electrophotographic developer.

Various electrophotographic methods, typified by the Carlson process, are well known to those skilled in the art. There is a method of transferring and fixing a toner image formed on a material to a transfer paper, and various studies have been conducted and used on dry developers used in these methods. Among these developers, various proposals have been made regarding developers (toner materials) to which capsule technology is applied. For example, JP-A-48-71648 discloses a toner material consisting of a mixture of toner particles and toner-fixing particles made of a toner-fixing material contained in a capsule body;
Publication No. 75032 discloses a toner material comprising a colorant selected from the group consisting of dyes, dyes, and mixtures thereof and an adhesive soft solid core material encapsulated in a shell material.

Toner images obtained by developing with toner materials such as those described above can be fixed by applying pressure to the toner materials. However, when the above-mentioned toner material is pressurized and fixed, the capsule wall (i.e. grain) is destroyed, but this destroyed capsule wall material remains as it is, making the image unclear, and Makes retention incomplete. In other words, the destroyed wall material of the capsule may be interposed between the transfer paper and the colorant and prevent the adhesion between the colorant and the transfer paper, or this adhesion may be hindered to ensure sufficient fixing. There are also drawbacks such as the need for high pressure.
The present invention has been made to eliminate these drawbacks, and is characterized by dissolving the capsule wall material after the capsule is destroyed.

The developer or toner material of the present invention is comprised of a mixture of at least two encapsulated toner materials. Capsules and capsules will be explained. A capsule is a capsule containing a colorant (or a colorant and a resin as a fixing agent) and a solvent _A1 for dispersing the colorant in a capsule wall material _B1 ; (or a coloring agent and a resin as a fixing agent) and a solvent A ₂ for dispersing it in a wall material B ₂ of the capsule, and the solvent A ₁ of the capsule is the wall material B of the capsule. ₁
but can dissolve the capsule wall material _B2 , the capsule solvent _A2 is
It does not dissolve its wall material _B2 , but it can dissolve the capsule wall material _B1 . Therefore, after forming a toner image using a toner material composed of a capsule and a mixture of the capsules, when pressure is applied to the toner material to destroy the capsule, the capsule and the solvent contained in the capsule are released. A ₁ and A ₂ flow out and mutually dissolve the wall material of the other capsule, and the wall material of the destroyed capsule does not remain intact. Therefore, a dispersion of colorant, resin (fixing agent) and wall material in a solvent is obtained, and an image is formed by this dispersion, so that the colorant is applied to the substrate (e.g. transfer paper). It adheres firmly to the surface and provides clear images.

The invention will be explained below with examples. The capsules used to make up the toner are as follows:
Different types of capsules were prepared.

Preparation of capsules: 1 g of carbon black (manufactured by Mitsubishi Kasei, Mitsubishi 44)
5 of lauryl methacrylate (molecular weight 10.000)
% toluene solution for 30 minutes using an ultrasonic disperser. Add 30g of this dispersion to NaOH.
10% aqueous solution of gum arabic with pH adjusted to 10 500
ml, use a homomixer to emulsify and disperse until the particle size of the emulsion becomes 5 to 15μ, and then raise the temperature of the dispersion to 40 to 42℃ on a water bath.
Keep it for 30 minutes. To this was added 100 ml of a 10% gelatin (isoelectric point 8.8) aqueous solution whose pH was adjusted to 10 with NaOH. While keeping the temperature of the dispersion liquid at 40 to 42℃ and stirring with a three-one motor, 1% acetic acid aqueous solution was gradually added dropwise over 2 to 2.5 hours to bring the pH from 10 to 10.
It dropped to 4.4. Next, 100 ml of ion-exchanged water at 0°C was added, and while the dispersion container was externally cooled with ice, stirring was continued using a three-one motor, and the temperature of the dispersion was raised to 5-6°C for 30 minutes.
Stirring continued for a minute. 5 ml of a 37% formalin solution to make the capsule walls insoluble in water.
was added, the pH was raised to 7 with NaOH, the solution was heated on a water bath, and the temperature of the liquid was raised to 50°C at a rate of 2°C per minute to complete the encapsulation process.

The above capsule slurry was heated using a Niro spray dryer, with an inlet temperature of 180℃ and an outlet temperature of 80-85℃.
℃, atomizer pressure of 4.8 to 5.5 Kg/cm ² and a slurry dropping rate of 10 ml/min. Powdered capsules were obtained containing a liquid in which black and lauryl methacrylate as a fixing agent were dispersed in toluene.

Preparation of capsules-': To 1 liter of the capsule slurry obtained in the preparation of the above capsules, 10 g of polystyrene latex emulsion (0602 latex emulsion manufactured by Nihon Gosei Rubber Co., Ltd.) was added as a solid content, and the above-mentioned capsules were prepared. The capsule wall is composed of an inner wall made of gelatin and gum arabic, and an outer wall made of polystyrene, and the inside of the capsule is In the same manner as above, powdered capsules containing a toluene dispersion of carbon black and lauryl methacrylate were obtained.

Preparation of capsules: 1.5 g of carbon black (manufactured by Mitsubishi Kasei, Mitsubishi 44) was dispersed for 30 minutes in 100 ml of a 5% ion exchange aqueous solution of polyoxyethylene sorbitan monooleate using an ultrasonic disperser. 10% methylene chloride solution of polystyrene (Etsuso Standard Oil Co., Ltd., D-125) to which 1 g of sodium di-2-ethylhexylsulfosuccinate was added as a dispersant.
Add the above dispersion to 100ml, emulsify and disperse using a homomixer until the particle size of the emulsion becomes 5 to 15μ, and add 1L of 5% gelatin (isoelectric point 5.5) aqueous solution with pH 7 at 40°C while stirring. Add the above dispersion liquid and use a homomixer to emulsify and disperse until the particle size of the emulsion becomes 20 to 30μ to prepare a composite emulsion.This emulsion is then mixed with a three-one motor until the odor of methylene chloride disappears. Heating and stirring were continued for about 2 hours. The slurry obtained in this way is used as a capsule.
In the same way as in the case of , powdered capsules are made by spray drying using a Niro spray dryer, and the walls of the capsules are made of polystyrene, and the capsules contain a liquid dispersion of carbon black as a coloring agent in water. I got -.

The capsules prepared as above and the capsules were mixed in a ratio of 1:1, and this mixture
A developer is prepared by adding 100 parts by weight of iron powder (Nippon Iron Powder Co., Ltd., EFV) as a carrier to the weight part, and this developer is used in an electrophotographic copying machine (Ricoh PPC copying machine). Then, the toner image formed on the transfer paper is transferred to 100% by a variable pressure pressure fixing machine.
When the toner image was fixed with a pressure of Kg/B-4, the toner image was sufficiently fixed, but the copied image was not sufficiently clear.

In the above, the developer was prepared and the toner image was copied in exactly the same manner as above, except that capsule-' was used instead of capsule-, that is, capsule' and capsule- were mixed. Pressure fixing was performed, and in this case, sufficient fixing and clear copied images were obtained.

The outer wall of the toner made of the above capsules is made of hydrophilic resin such as gelatin and gum arabic, and it easily adsorbs water.When mixed with a carrier, the amount of charge on the toner due to frictional electrification is small, and as a result, the toner is It causes staining of the background of photosensitive materials. Capsule-' has a polystyrene coating on the outside of the gelatin and gum arabic wall, which makes it difficult to adsorb water, and has high electrical resistance, so it generates a large amount of triboelectric charge, resulting in a clear, clean surface without any stains. An image is obtained. Therefore, by using a developer comprising a mixture of capsules and capsules, a clear copy image with excellent fixing properties can be obtained.

In the developer obtained by mixing capsules and capsules in the above, only toluene exists as a solvent, and there is no solvent, that is, water, which dissolves gelatin and gum arabic, so when such a developer is used, As mentioned above, the gelatin and gum arabic remain as they are, and a clear image with excellent fixing properties cannot be obtained.

Claims (1)

[Claims] 1. In an electrophotographic developer consisting of a mixture of at least two types of capsules containing at least a colorant and a solvent in the capsule wall, the solvent contained in one capsule is contained in the wall material of the capsule. The electrophotographic developer described above is characterized in that the capsules are constructed so as to dissolve wall materials of other capsules without dissolving the other capsule wall materials.