JPS58132245A - Image formation - Google Patents

Abstract

PURPOSE:To prevent generation of photographic fogs upon copying for a long time in the formation of reversal toner images by developing with one component type magnetic brushes by operating a developing device only in the stage of developing. CONSTITUTION:For example, conductive toners contg. magnetic powder such as magnetic iron oxide are used as toners, and a developing device provided with a magnetic roll 1 which can rotate relatively in a cylindrical conductive sleeve 2 is used. In order to perform reversal development, that is, such toner development wherein the toners are stuck on the parts where electric charge is annihilated by image exposure, voltage is applied between the sleeve 2 and a conductive substrate 4 which is a photosensitive material. The development is accomplished by rotating the roll 1 or rotating the sleeve 2 or rotating both in mutually different directions while supplying the toners from a hopper 3 to the surface of the sleeve 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an image by electrophotography, and the present invention relates to a method for forming a reversal toner image by electrophotography using -component magnetic brush development. As shown in Fig. 1, the Uko method, which has come to be used as a one-component magnetic brush current method, has a relatively rotating magnetic roller 1 inside a cylindrical conductive sleeve 2. The conductive toner with magnetism in 3 is supplied to the sleeve surface from the core 1-5, and the magnetic roller 21
Or, as the sleeve 2 rotates, it moves along the outer periphery of the sleeve, and a part of the sleeve 2 adheres to the swollen electrostatic latent image 6 formed on the photoconductive layer 51C on the conductive substrate 4 of the photosensitive material, thereby forming the toner image 1. (positive development). In such positive development, first, the photoconductive layer of the photosensitive material is uniformly corona charged in a dark place to give the layer surface a positive or negative charge. When the photoconductive layer is imagewise exposed in this state, the charges in the exposed areas disappear, and charges remain only in the non-exposed areas to form an electrostatic latent image, which is developed with toner as described above to form a toner image. shall be. This developing method has a relatively simple device and can be used even if the diameter of the sleeve or magnetic roller is small, so it is a preferable method when miniaturizing the electrophotographic device. The obtained toner image is fixed as it is or after being transferred to plain paper or the like.

On the other hand, when copying from microfilm by electrophotography, for example, a so-called reversal development method is used, in which a charged photoconductive layer is imagewise exposed and toner is attached only to the exposed areas, that is, the areas where the charge has disappeared. It becomes necessary. To perform reversal development using the one-component magnetic brush development method 2 as described above, as shown in Section 2, a bias voltage is applied between the conductive sleeve 2 and the conductive substrate 4 of the photosensitive material. When the charge on Shun 6 is positive, the sleeve side is connected to the power supply 8, and when the charge is negative, the sleeve side is connected to the power supply 8. Since the toner has the same polarity as the polarity applied to the sleeve, the toner has the same polarity as the electric charge on the electromagnetic material 6, and is repelled and does not adhere to this part. On the other hand, a relative potential difference exists between the exposed area, that is, the area where there is no charge, and the toner particles, and the toner is attracted and adheres only to this area, forming a toner self (reversal development).

As explained above, in the case of reverse development and #, compared to the case of normal development described above, there is a bias in the factors that determine the conditions for the movement and adhesion of toner particles from the conductive sleeve to the conductive substrate on the photosensitive material. The addition of one element, the voltage, creates a rough and delicate surface on the image forming mechanism.

By the way, in order to perform copying by reversal development using a -component magnetic brush method, after the photosensitive material is charged and imagewise exposed as described above, reversal development is performed, and the resulting toner is either fixed directly or supplied separately. After being transferred to flexible paper, film, etc., it is fixed, but in order to simplify the series of operations, the developing device is operated continuously, or it is linked to the drive of the motor for rotating the drum or moving the paper, etc. It's moving. Therefore, when developing a part of a document, the developing device itself is not operated during the operating period other than the actual developing period, that is, during the charging, exposure and fixing periods (for example, about 15 seconds compared to the developing time of 2 to 6 seconds). (rotating one or both of the sleeve and magnetic roll). However, if this type of copying operation using reversal development is continued, capri (in other words, toner adheres to non-exposed areas where electric charges exist) will gradually occur, and the image will become smudged. A problem arose.

The inventors of the present invention investigated the cause of the occurrence of such capri, and found that the occurrence of such capri occurs when the developer is continuously operated during a series of copying operations to obtain the required number of copies. If you find out that this is caused by running the developing unit for 10 minutes or more,
In other words, the average length of toner staying on the sleeve is 10
It has been found that when the time exceeds 10 minutes, the occurrence of capri becomes noticeable in subsequent copied images. Although the reason for this is not clear, it is believed that when the toner continues to move along the sleeve surface VC for a long time, the surface condition of the toner changes, causing a subtle change in resistance.

Based on the above knowledge, the present inventor has determined that when performing a copying operation using reversal development, the developer is operated only during development, and when operations other than development such as charging, image exposure, and fixing are being performed, the developer is operated. It was discovered that by discontinuing the operation of the machine, clear copies could be obtained without any occurrence of capri even if copying was continued for a long time.

The invention has been completed.

That is, in forming a reversal toner image through the steps of charging, image exposure, toner development, and fixing, including a reversal development step using a component-based magnetic brush development, the developing device is operated only during development. This is an image forming method characterized by:

The present invention will be explained in detail below.

The photosensitive material used in the present invention is one in which a photoconductive layer is provided on a metal plate such as aluminum or a paper or film subjected to conductive treatment, and the photoconductive layer includes a vapor deposited layer of selenium, zinc oxide, A layer in which inorganic photoconductor powder such as cadmium sulfide is dispersed in a binder, or polyvinylcarnoζ
A layer of an organic photoconductor such as sol, poly-N-vinylcarbazole, etc. is used.

In the present invention, the above photosensitive materials are used.

An image is formed through a series of steps including charging treatment by corona discharge, image exposure, reversal development by -component magnetic brush development, and fixing (or transfer and fixing). As the corona discharge, one commonly used in electrophotography is used, and the corona discharge may be charged either positively or negatively. Image exposure is image exposure when it is desired to obtain a negative-positive copy, such as copying from a microfilm, and a suitable optical system is used. Upon imagewise exposure, the charge on the photoconductor layer is dissipated in the exposed areas, forming an electrostatic latent image. The photosensitive material on which the electrostatic latent image has been formed is then transferred to a development area and subjected to reversal development. In the present invention, a developing device as shown in FIG. 2 is used in which a magnetic roller 1 that can rotate relative to each other is provided within a cylindrical conductive sleeve 2. As the toner, for example, a conductive toner containing magnetic powder such as magnetic iron oxide is used. The toner particle size is generally about 0.
It is preferably 5 to 100 microns and spherical. In the present invention, a voltage is applied between the conductive sleeve 2 and the conductive substrate 4 of the photosensitive material in order to perform reversal development, that is, toner development in which toner is attached to the portion where the charge has disappeared during image exposure. do. In this case, for example, if the electrostatic latent image is formed by positive charges, the sleeve side should be positive, and if the electrostatic latent image is formed by negative charges, the sleeve side should be Apply voltage so that it becomes negative. For development, the magnetic roller 1 is rotated while toner is supplied from the hopper 6 to the surface of the conductive sleeve 2.

Either the sleeve 2 is rotated, or both are rotated nine times in different directions (expressed as "relatively rotating magnetic rollers" in the present invention). In any case, the developing device is operated by rotating the magnetic rollers relative to each other. For example, in the case of an electrostatic latent image consisting of a positive charge, as shown in M, a voltage is applied between the conductive sleeve 2 and the conductive substrate 4 so that the sleeve side is positive, and the photosensitive material is transferred to the developing drum. Reversal development is performed by operating the developing device while overflowing with water. That is, since the toner is positively charged, it is repelled by the charged portion 6,
A relative potential difference is created between the toner and the portion where no charge exists, and the toner adheres only to this portion. The obtained toner image may be directly fixed by any method such as heat fixing, pressure fixing, solvent fixing, etc., or may be transferred to plain paper and then fixed by a similar method.

In an electrophotographic copying method consisting of a series of steps as described above, the present invention operates a developing device only when developing a photosensitive material, and stops operating the developing device when no photosensitive material is present in the developing area. Alternatively, the idling operation of the developing device is stopped by stopping the rotation of the sleeve.

By doing so, it is possible to prevent the occurrence of capri during reversal development, which is thought to be caused by idle operation of the developing device as described above, and it is possible to obtain clear images even if copying is continued for a long period of time. Various means can be considered to stop the operation of the developing device other than during development. For example, sensors are installed before and after the developing area, and when the photosensitive material enters the developing area, the leading edge of the photosensitive material is caught and a magnetic roller or sleeve is activated. Rotate it, and when the photosensitive material leaves the development area, it catches the rear end and stops the rotation of the magnetic roller or sleeve.

As described above, according to the present invention, when reversal development is performed using a component-based magnetic brush developer, the developer is operated only during development, and by preventing idle operation of the developer, toner particles are It is possible to reduce the residence time on the sleeve, prevent the occurrence of capri, and obtain clear copies without capri even if copying is continued for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing normal development by one-component magnetic brush development, and FIG. 2 is an explanatory diagram showing reversal development. In the figure, 1 is a magnetic roll and 2 is a conductive sleeve. 5 is a hopper, 4 is a conductive substrate. 5 is a photoconductive layer; 6 is an electrostatic latent image. 7 is a toner image, 8 is a bias power supply. It is. (6 others)

Claims (2)

[Claims] (1) - In a method of forming a reversal toner image through the steps of charging, deep exposure, toner development, and fixing, including a reversal development step using component-based magnetic brush development, only during development (operating the developing device) A method for forming both stools. (2) - A component-based magnetic plan developing device is composed of a cylindrical conductive sleeve and a magnetic roller rotatably housed within the sleeve, and the photosensitive material to be developed is a conductive substrate and a conductive substrate. An image according to claim 1, comprising a trapped photoconductive layer, wherein reversal toner development is effected by applying a bias voltage between the conductive sleeve and the nuclear conductive substrate. Formation method.