JPS5921550B2 - How to develop an electrostatic latent image - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developing method using a conductive magnetic toner as a developer for visualizing an electric latent image formed by electrophotography or electrostatic recording.

Generally, various methods have been proposed for dry development, of which the cascade method and the magnetic brush method are representative.

However, the former cascade method has drawbacks such as difficulty in reproducing halftones, an increase in the size of the developing device, edge effects, and contamination of the device due to toner scattering.

The latter magnetic brush method has advantages such as a small developing device, good halftone reproducibility, no edge effect, and little toner scattering, but it uses a developer that uses a mixture of a magnetic carrier and charged colored toner. Because of this, when the toner content decreases, the image density decreases and furthermore, carrier adheres to the image area. Conversely, when the toner content ratio increases, toner adheres to non-image areas, resulting in fog. For this reason, various devices are required to keep the toner content ratio constant, and the developing device itself becomes complicated. Furthermore, the triboelectric charging properties of the carrier in this developer deteriorate over time, resulting in disadvantages such as the hassle of replacing the carrier. Therefore, as a method to eliminate the above-mentioned drawbacks, a developing method using a carrierless developer, that is, a magnetic toner has been considered, and various methods have been proposed for imparting an electric charge to this magnetic toner. For example, A: a method in which charges are injected from a sleeve using conductive magnetic toner; B: a method where an insulating toner is charged by contact with an electrostatic image support; C: a method where an insulating toner is charged by stirring; D: There is a method of applying a charge to the surface of highly insulating toner by using corona discharge. Of these methods, method A in particular uses an electric field between the electrostatic image support and the sleeve to inject charges into the conductive toner through the sleeve. In some cases, the density is sufficient, but the toner adheres to the non-image areas where the line width of characters and graphic patterns is narrow, causing background stains. There were drawbacks such as a trailing phenomenon that appeared in the non-image area, like a shadow in the pattern. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for developing an electrostatic latent image that can form a recorded image of excellent quality using a conductive magnetic toner.

In order to achieve this object, the present invention uses a conductive magnetic toner having extremely high conductivity as a developer.

Hereinafter, it will be explained in detail using examples.

FIG. 1 is a cross-sectional side view showing an embodiment of the electrostatic latent image developing method according to the present invention.

In the figure, 1 is an electrostatic recording paper consisting of a base paper 1a, a conductive layer 1b, and a recording layer 1c, the details of which are shown in FIG. 3 is a highly conductive magnetic toner; 4 is a toner reservoir that stores the highly conductive magnetic toner 3 and supplies it as needed; 5 is a non-magnetic and conductive toner; The sleeve 6 is the highly conductive, magnetic toner 3 that is inserted into the sleeve 5.
A cylindrical or cylindrical rotatable magnet roll T, in which magnetic poles of opposite polarity are alternately magnetized, is provided on the sleeve 5 in order to convey the magnet while rotating it along the surface of the sleeve 5. This is a regulating member that regulates the amount of highly conductive and magnetic toner 3. In order to simplify the following explanation, it is assumed that the sleeve 5 does not rotate and is fixed A, and the guide plate 2 and the sleeve 5 are electrically grounded.

Further, as a method for forming an electrostatic latent image on the electrostatic recording paper 1, a needle electrode (not shown) is provided close to the recording layer 1c, and a high voltage is applied between the needle electrode and the conductive layer 1b. This is realized by applying a potential to the recording layer 1c. Here, the recording layer 1e
When the discharge voltage determined by the characteristics of the recording layer 1c is defined as V+b, the potential of the electrostatic latent image formed on the recording layer 1c is this +
HI). If the above voltage exists on the recording layer 1c, by bringing a grounded metal into contact with the surface, a discharge will occur up to +h, but the voltage will not drop below V+h. It was also confirmed that if the potential on the recording layer 1c is V+h or less, the potential does not change even if the surface is brought into contact with a grounded metal.
Generally, the potential of an electrostatic latent image formed on electrostatic recording paper is often equal to or less than +h. This shows that even when a highly conductive toner is used during development, the electrostatic latent image on the electrostatic recording paper is not disturbed and it is possible to develop a high quality image. Then, by passing the electrostatic recording paper 1 having this electrostatic latent image between the guide plate 2 and the sleeve 5,
Highly conductive/magnetic toner 3 can be attached and developed. At this time, the distance between the guide plate 2 and the sleeve 5 is set such that the highly conductive magnetic toner 3 is always in contact with the surface having the electrostatic latent image. In addition, the composition of the highly conductive, low-resistance magnetic toner 3 is, for example, made of 50% polyethylene acrylic polymer, 30% magnetic iron oxide, and 20% carbon black in weight ratio. , powder with a particle size of 5 to 40 μm and used as a toner. The conductivity of this toner was determined from the IV characteristics when 100η was placed in a 3.3φ circular tube and pressed from both sides with a force of 50R/(Yn2.This IV characteristic was approximately Shows Ohmic characteristic, 10m0hS/at 100V/demand
The conductivity of C7n was shown. Furthermore, magnetic toners with a conductivity of 102m0hsh can be made with a large amount of carbon, and the results of development experiments using these magnetic toners with a conductivity of 10-102m0hT have shown that they have high optical density with little background smearing. A record with a high quality image was formed. Although the toner composition shown here is capable of heat and pressure fixing, by changing the resin, it can be used for heat fixing, pressure fixing, etc.
It is also possible to make toners for solvent fixing and for combination fixing. Furthermore, if fixing is not required, magnetic metal particles may be used as the developer. At this time, the conductivity of the toner is as high as 10 mOhVi. Next, development of an electrostatic latent image with the above configuration will be explained with reference to FIG. 3.

Here, to simplify the explanation, the highly conductive/magnetic toner 3 is shown in contact with three circles 3a, 3b, and 3c, and states 1 and 2 indicate the order in the developing process, and development is completed in state 1. .

First, if the electrostatic latent image formed on the recording layer 1c of the electrostatic recording paper 1 has negative polarity, for example, the electrostatic latent image formed on the recording layer 1c on the side opposite to the developing device, that is, on the recording layer side in contact with the conductive layer 1b, has a positive polarity. An electrostatic latent image ▲ is formed, and this positive electrostatic latent image is caused by negative charges induced from the grounded guide plate 2 being formed in opposition within the conductive layer 1b. Sometimes, it is only necessary to consider the negative electrostatic latent image formed on the developing unit side of the electrostatic recording paper 1.

Therefore, when the magnet roll 6 rotates clockwise, the highly conductive magnetic toner 3 rotates counterclockwise on the sleeve 5.
It revolves and rotates. First, in state 1, highly conductive magnetic toner 3 maintains a neutral state, but in state 1, highly conductive magnetic toner 3 comes into contact with a negative electrostatic latent image. Therefore, positive charges flow into the highly conductive magnetic toner 3 from the grounded sleeve 5, and the highly conductive magnetic toner 3
Since it is positively charged, it is attracted by the electrostatic latent image and Coulomb F. When this Coulomb force F becomes larger than the force M with which the highly conductive magnetic toner 3 is attracted by the magnet roll 6, the highly conductive magnetic toner 3 remains attracted to the electrostatic latent image, and development is delayed. Complete. Note that the electrostatic recording paper 1
Besides, an electrophotographic photosensitive plate 8 having a three-layer structure shown in FIG. 4 can be used.

This electrophotographic photosensitive plate 8 includes a conductive substrate 8a and a photoconductor layer 8.
b and a transparent insulating layer 8c. In this case, it goes without saying that the electrophotographic photosensitive plate 8 is used in a state in which no discharge occurs even if the potential on the electrophotographic photosensitive plate 8 comes into contact with a grounded metal. In addition, although the structure of the developing device has been described in which the magnet roll 6 is rotated and the sleeve 5 is fixed, it is assumed that the magnet roll 6 is fixed.
Of course, the sleeve 5 may be rotated, or the magnet roll 6 and the sleeve 5 may be rotated together.

Further, although the sleeve 5 has been described as being conductive, it may be insulating, and in this case, the toner storage device 4 and the regulating member 7
It is only necessary that the electrode is conductive and grounded, and it goes without saying that a grounding plate may be provided at a position where it is in constant contact with the magnetic layer 3. Further, the guide plate 2 may be used in a grounded state at all times, but there is no particular need to ground it if the conductive layer 1b of the electrostatic recording paper 1 is used grounded elsewhere. Also,
The above explanation is about using highly conductive/magnetic toner in a grounded state, but if you use highly conductive magnetic toner, it is possible to form recordings of the same quality as when grounded, even without grounding. .

In this case, the range in which a clear image can be formed becomes narrower, and the ratio of the conveying speed V of the recording member to the conveying speed VD of the magnetic toner becomes K.
Then, K=10 to 2.5×10, and when grounded, K=3×− to 2.

It is 5×10.

Furthermore, when a highly conductive magnetic toner is used, high-speed development becomes possible, and excellent recorded matter can be formed even when paper is fed at 100 CWI/S.

As described above in detail, the electrostatic latent image developing method according to the present invention provides high recording density with little background smudge.
Moreover, it is possible to form a recorded matter that can be developed uniformly.

Moreover, it has effects such as excellent characteristics for high-speed development.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional side view showing an embodiment of the electrostatic latent image developing method according to the present invention, FIG. 2 is a cross-sectional view showing the detailed structure of the electrostatic recording paper shown in FIG. 1, and FIG. A diagram for explaining the operation of FIG. 1, and FIG. 4 is a sectional view showing the structure of an electrophotographic photosensitive plate that can be used in FIG. 1... Electrostatic recording paper, 1a... Base paper, 1
b... Conductive layer, 1c... Recording layer, 2.
...Guidance board, 3...Conductive magnetic toner,
4... Toner storage device, 5... Sleeve, 6... Magnet roll 7... Regulating member, 8... Electrophotographic photosensitive plate , 8a... conductive substrate, 8b... photoconductor layer, 8c...
・Transparent insulation layer.

Claims (1)

[Claims] 1 In a method of developing a charge image formed on the surface of an electrostatic charge image support using a conductive magnetic toner as a developer, when the conductive magnetic toner is used in an electric field of 100 V/cm, 1
A method for developing an electrostatic latent image, characterized by using a toner having a high conductivity of 0^-^2 to 10^4 mohs/cm.