JPH0132981B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a multicolor electrophotographic method, and more particularly to a multicolor electrophotographic method that exhibits excellent multiple transfer properties. Conventionally, electrostatic printing method or electrophotographic method is well-known as a method for visualizing an electrical latent image using a developer. For example, for electrophotography, USP2297691
Specification, Special Publication No. 23910, Special Publication No. 43-
Various methods described in Publication No. 24748 and the like are well known. Generally, a photoconductive substance is used to form an electrical latent image on a photoreceptor exhibiting photoconductivity by various means, and the latent image is then developed with a developer to obtain a visible image; Alternatively, if necessary, a toner powder image is transferred to paper or the like and then fixed by an appropriate means to obtain a visible image. In order to obtain a color multicolor image, the original is exposed using a color separation filter, and the above process is repeated with yellow,
This process is repeated multiple times using color developers such as magenta and cyan to superimpose toner images to form a color image. Therefore, in order to transfer a toner powder image onto a transfer material such as paper and obtain a color image, the second color is transferred onto the transfer material on which the first color toner powder image has been transferred, and then the third color is transferred on top of that. It is necessary to perform multiple transfers in which different colors are transferred, which causes various problems compared to black and white copying in which only one transfer is normally performed. For example, the transfer efficiency of the toner powder image transferred to the second and third colors may decrease in the solid area, and the desired hue may not be reproduced, or the toner of the second and third colors may scatter around the line area. , characters become blurred and sharpness decreases, and other phenomena have been observed. In view of the above circumstances, it is an object of the present invention to provide a multicolor electrophotographic method having excellent multiple transfer properties. In other words, in the present invention, the toner transferred to the second color is larger than the toner transferred to the first color, and
The amount of triboelectric charge of the toner in each developer is controlled so that the toner transferred to the third color has a larger amount of tribocharge than the toner transferred to the second color, and it is good even if the transfer electric field changes. The present invention provides a multicolor electrophotographic method that provides excellent multi-transfer performance by combining developers that ensure excellent transfer performance. The inventor of the present invention focused on and studied the fact that there is a difference in transferability between when the same toner is transferred to the first color and when it is transferred to the second or third color. As a result, (1) Difference in transferability (2) The transferability under a constant transfer electric field depends on the amount of triboelectric charge. (3) The value of triboelectric charge when transferability is almost saturated depends on the transfer method and toner type. We obtained findings such as that it cannot be determined unambiguously because it differs depending on the transfer material and the transfer material. Based on these, studies were conducted as described later in Examples and Comparative Examples, and it was found that multiple transfer can be made good by increasing the amount of triboelectric charge in accordance with the transfer order. In the present invention, any method is preferable for controlling the amount of triboelectric charge of the plurality of developers used, and there are no limitations. For example, a method of controlling the charge by changing the type and amount of an additive called a charge control agent in the toner, a method of controlling the charge by changing the charging characteristics of a binder resin in the toner, or a method of controlling the charge by changing the toner manufacturing process. There are two methods, such as a method in which the amount of heat is controlled by controlling the amount of heat, and a method in which the carrier carrier in the developer is appropriately processed and controlled. As for the constituent components of the developer used in the present invention, such as colorants, binder resins, various additives, carriers, etc., conventionally known components can be widely used. For the amount of triboelectric charge of the toner transferred first,
The amount of triboelectric charge of the toner to be transferred next is an absolute value.
It is good that it is 30% or more (more preferably 45% or more) larger. Here, the amount of triboelectric charge is measured by the blow-off method. That is, the developer is held by a magnet, the toner particles in the developer are forcibly attracted, and the charge amount Q and weight M of the attracted toner are measured.
Calculate Q/M and use it as the triboelectric charge amount. Embodiments of the present invention will be described below with reference to the drawings. First, an example of a color electrophotographic copying machine to which a multicolor electrophotographic method according to the present invention is applied will be described with reference to FIG. The electrostatic latent image formed on the photosensitive drum 1 by a suitable means is made visible by the developer in the developing device _16-1 , and is applied to the transfer material already held on the transfer drum 19 by the gripper 20. A developed toner powder image is transferred by a transfer corotron.
Furthermore, the toner powder image developed by the developer in the developing device 16-2 as _{the second} color is also transferred onto the transfer material by the transfer corotron 21, and the same process is performed for the third color. In this manner, the transfer drum 19 rotates a predetermined number of times while holding the transfer material, and images of a predetermined number of colors are multiple-transferred. The developer in the first color developing device _16-1 , the developer in the second color developing device 16-2, and the developer in the _third color developing device _16-3 are configured as shown in the table below. did. (All parts in the table indicate parts by weight)

[Table] As a result, the color reproduction was more faithful to the original than in the comparative example described later in the black area where three color toners overlap, and the blue area, green area, and red area where two color toners overlap. In addition, the line part also exhibited a sharp black color, and a clear full-color image was obtained. On the other hand, when a developer with the following composition was used as a comparative example, solid black areas became reddish black, blue areas became purple, green areas became yellow-green, red areas became orange, and line areas became orange. However, only a reddish and unclear image could be obtained.

【table】 [Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing a color electrophotographic copying machine to which the multicolor electrophotographic method of the present invention is applied. 1...Photosensitive drum. 16...Developing section. 19...Transfer drum. 20...Gritzpur. 21...Transcription corotron. 22... Separation claw.

Claims (1)

[Claims] 1. Multicolor electrophotography, comprising the steps of transferring a toner onto the surface of a transfer material, and transferring a toner of a different color and having a larger absolute value of triboelectric charge than the toner onto the surface of the transfer material. Method.