JPS6251468B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic recording device, and in particular to an electrostatic recording device that uses a magnetic toner that has a developing effect on positive and negative charge images, and is designed to effectively develop only one charge image. This invention relates to an improved electrostatic recording device.

As is well known, a developer is required for electrostatic recording with an electrostatic recording apparatus using an electrostatic recording method. Conventionally,
There are two types of developers: two-component developers made of iron powder and toner, and one-component magnetic toner (so-called magnetic toner) in which the toner itself has magnetism. In general, the former, two-component developer, is mainly used as a developer for an electrostatic recording device using an electrostatic recording method. Although magnetic toner has extremely superior maintainability compared to two-component developers, it has the ability to develop both positive and negative charge images, so electrostatic recording This is because it has the disadvantage that background fog occurs when the medium is used repeatedly. This occurs because the residual charge on the electrostatic recording medium is incompletely erased during repeated use, resulting in it being charged either positively or negatively.

Note that the above-mentioned maintainability refers to the management of the recording density of the toner. That is, the two-component developer has the disadvantage that toner is consumed each time it is developed and only iron powder remains, making it inconvenient to manage recording density. However, magnetic toner does not contain iron powder unlike two-component developers, and has the advantage that recording density can be easily controlled.

On the other hand, the recording voltage applied to the electrostatic recording needle during electrostatic recording is preferably as low as possible in order to avoid the formation of discharge between adjacent electrostatic recording needles. For this reason, it is known to previously charge an electrostatic recording medium to a polarity opposite to that of the recording voltage and to induce discharge with a low recording voltage. In this case, the recorded area and the unrecorded area of the electrostatic recording medium are charged with opposite polarities, and a developer such as a magnetic toner that has the ability to develop both types of charge images cannot record them. Both the recorded area and the unrecorded area are developed. For this reason, two-component developers that selectively develop only one charge image have been used.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrostatic recording device that can use magnetic toner and does not cause background fog.

In summary, this invention uses a magnetic toner that is easy to maintain and develops both charge images, so that one charge can be neutralized and only the other charge image can be effectively developed. This is what I did.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram schematically showing an electrostatic recording apparatus according to an embodiment of the present invention. In terms of structure, an electrostatic recording drum 1, which is an example of an electrostatic recording medium, includes a cylindrical metal drum 2 made of aluminum or the like, and a dielectric layer 3 formed on the outer periphery of the metal drum 2.
The metal drum 2 is grounded. A primary charger 4, which is an example of a first charging means, is disposed at a position facing the outer peripheral surface of the electrostatic recording drum 1 in order to charge the electrostatic recording drum 1. An electrostatic recording head 5 is provided at a position separated by a certain distance in the direction of rotation of the electrostatic recording drum 1 from the position where the electrostatic recording drum 1 is disposed. The electrostatic recording head 5 performs electrostatic recording on the electrostatic recording drum 1 charged by the primary charger 4. The electrostatic recording head 5 is composed of a large number of electrostatic recording needles arranged in the axial direction of the electrostatic recording drum 1.

A secondary charger 6, which is an example of a second charging means, is placed at a certain distance from the electrostatic recording head 5 in order to neutralize the charged portion of the electrostatic recording drum 1 that has not been recorded by the electrostatic recording head 5. A magnetic toner developing device 7 is provided between the electrostatic recording head 5 and the magnetic toner developing device 7. Secondary charger 4
is composed of a housing 10, a metal etched mesh electrode 11, and a corona wire 12. The metal etching mesh electrode 11 is integrally formed with the housing 10 in the form of a dot on the outer peripheral surface of the electrostatic recording drum 1, and has a linear density of 0.5 to 10 lines/mm and a light transmittance of 30% or more. There is. The corona wire 12 is configured inside the housing 10. Corona power supply 1 supplied to secondary charger 6
One end of the corona power supply 13 is connected to the corona wire 12, and the other end of the corona power supply 13 is connected to the housing 10 and the metal etching mesh 12 and grounded.

A magnetic toner developing device 7, which is an example of a magnetic toner developing means, uses a secondary charging device 6 to develop the portion of the electrostatic recording drum 1 that has not been neutralized by the secondary charging device 4.
The transfer charger 6 is provided between the secondary charger 6 and the transfer charger 8 at a certain distance from the transfer charger 8 . The magnetic toner developing machine 7 includes a storage case 7a that stores magnetic toner, and is configured such that a magnet roll 7b is rotatably supported in the storage case 7a. The magnet roll 7b is formed into a columnar shape with magnets arranged along its outer circumference. The transfer charger 8, which is an example of an electrostatic transfer means, transfers the electrostatic recording drum 1 on which magnetic toner has been developed by the magnetic toner developing device 7 onto the recording paper 14, which is an example of a transfer medium. The recording head 5 is provided under the same conditions as the electrostatic recording head 5 at a certain interval from the recording head 5. Transfer charger 8
is composed of a housing 8a and a corona wire 8b. One end of a power supply (not shown) supplied to the transfer charger 8 is connected to the corona wire 8b, and the other end of the power supply is connected to the casing 8a.

The recording paper 14 is connected to a transfer charger 8 and an electrostatic recording drum 1.
The material is fed through a gap provided between the outer circumference of the material and the outer circumference of the material.

A heating or pressure fixing device 15 is provided opposite the transport path of the recording paper 14.

A cleaner 9 is installed on the outer peripheral surface of the electrostatic recording drum 1 between the transfer charger 8 and the primary charger 4 in order to remove residual toner on the electrostatic recording drum 1 that has been transferred by the transfer charger 8. provided.

Next, the operation of this embodiment will be explained with reference to the drawings. FIG. 2 illustrates temporal changes in the surface potential of the electrostatic recording drum 1 of the embodiment shown in FIG. Here, for convenience of explanation, a case will be described in which the electrostatic recording drum 1 is positively charged by the primary charger 4. In order to avoid the formation of discharge from a large number of electrostatic recording needles, the electrostatic recording drum 1 is previously applied with a voltage V ₊ (usually a voltage of 350 V or less) lower than the discharge starting voltage of the electrostatic recording head 5 by a primary charger 4. be done. The surface potential of the electrostatic recording drum 1 at this time corresponds to FIG. 2A. That is, the surface potential of the electrostatic recording drum 1 is charged to a positive potential V ₊ by the primary charger 4, and remains at a positive potential V + while the electrostatic recording drum 1 rotates in the direction of the arrow to the position of the electrostatic recording head 5 _. is maintained. A negative recording voltage V _R having a polarity opposite to that of the positively charged electrostatic recording drum 1 is applied to the electrostatic recording head 5 corresponding to the printing area of the object. The surface potential of the electrostatic recording drum 1 at this time is shown in FIG. That is, the dotted line area in FIG. 2B corresponds to the non-printed area of the subject. Therefore, the negative recording voltage _VR is not applied to the electrostatic recording drum 1. Further, the solid line portion in FIG. 2B corresponds to the printed portion of the subject. Therefore, a negative recording voltage _VR is applied to the electrostatic recording drum 1. Therefore, the surface potential of the electrostatic recording drum 1 is charged to a positive potential depending on the portion not recorded on the electrostatic recording drum 1, and to a negative potential depending on the portion recorded on the electrostatic recording drum 1. The electrostatic recording drum 1 is connected to the secondary charger 6 in the direction of the arrow.
While rotating to the position, each surface potential is maintained. Next, a negative corona voltage Vd is applied to the corona wire 12 formed in the secondary charger 6 from one end of the corona power supply 13, and the casing 10 and the metal etching mesh 11 are connected to the other end of the corona power supply 13. and is grounded. Correspondingly, corona discharge is induced in the secondary charger 6 to generate negative corona ions. Corona ions generated in the secondary charger 6 can be extracted to the outside through the mesh of the metal etching mesh electrode 11. In addition, the corona electric field inside the secondary charger 6 is completely shielded and therefore has no charging ability. In this state, when the electrostatic recording drum 1, which includes a portion recorded with a negative charge, a portion recorded with a positive charge, and a portion not recorded with a positive charge, passes under the metal etching mesh electrode 11, The secondary charger 6 neutralizes only the positive potential portion of the portion that has not been recorded. At the same time as the neutralization is completed, the electric field that draws out the negative corona ions generated in the secondary charger 6 disappears. Therefore, neutralization automatically stops, and the surface potential of the portion not recorded on the electrostatic recording drum becomes zero potential. The temporal change in the surface potential of the electrostatic recording drum 1 at this time corresponds to the dotted line in FIG. 2C. On the other hand, the portion recorded on the electrostatic recording drum 1 has a negative potential, and only negative corona ions are generated in the secondary charger 6, so the surface potential of the electrostatic recording drum 1 does not change at all. It is retained without any problem. The surface potential of the electrostatic magnetic drum 1 at this time corresponds to the solid line portion in FIG. 2C. In this manner, the electrostatic recording drum 1 that has passed under the secondary charger 6 is held at a negative potential in the recorded portion, and at zero potential in the unrecorded portion. after that,
The electrostatic recording drum 1 develops only the portion recorded as a negative charge image by the magnetic toner developing device 11. That is, as the magnet roll 7b rotates, the magnetic toner stored in the storage case 7a is brought to the outer peripheral surface of the electrostatic recording drum 1. A corona voltage is applied to the corona wire 8b of the transfer charger 8 to induce corona discharge within the transfer charger 8.
The corona discharge generated in the transfer charger 8 attracts the developed magnetic toner on the electrostatic recording drum 1 to the recording paper 14 and causes the toner to be transferred. The recording paper 14 that has undergone toner transfer is brought to the fixing device 15 to complete the copying.
On the other hand, the electrostatic recording drum 1 further rotates, residual magnetic toner is removed by the cleaner 9, and the above recording process is repeated again.

In addition, although the polarity of the primary charger 4 is described as positive in the above description, it may be negative polarity. In this case, the applied voltage polarity in each of the other steps may be selected to be opposite to the polarity described above.

Further, although the case where recording paper is used as the toner transfer medium has been described, the present invention is similarly applicable to the case where other transfer medium such as a plastic stick is used, for example. Furthermore, although an electrostatic recording drum with a dielectric layer provided on the outer periphery of a metal drum was used as an electrostatic recording medium, the electrostatic recording medium is not limited to a specific structure; An electrostatic recording film or an electrostatic recording belt comprising a metal electrode and a dielectric layer may also be used. In other words, this invention makes it possible to use a magnetic toner by newly providing a shield type secondary charger that can selectively erase only one polarity of charge image after forming a charge image for printing. However, as long as this condition is met, there is no restriction by other specific components.

As described above, according to the present invention, by providing a shield type secondary charger that can selectively erase only one charge image, magnetic toner can be used as a developer and can be easily maintained. Using this method, a unique effect can be obtained in that fogging can be prevented when the electrostatic recording medium is used repeatedly.

It should be noted that the present invention is not limited to electrostatic recording devices, but can be widely applied to recording means such as facsimiles and printers.

[Brief explanation of the drawing]

FIG. 1 is an illustrative view of an electrostatic recording device according to an embodiment of the present invention. FIG. 2 is a diagram showing the surface potential of an electrostatic recording medium and changes over time to explain the operation of FIG. 1. In the figure, 1 is an electrostatic recording drum, 2 is a metal drum, 3 is a dielectric layer, 4 is a primary charger, 5 is an electrostatic recording head, 6 is a secondary charger, 7 is a magnetic toner developer, and 8 is a A transfer charger, 9 a cleaner, 10 a housing, 11 a metal etching mesh electrode, 8b and 12 a corona beam, 13 a corona beam, 14 a recording paper, and 15 a fixing device.

Claims (1)

[Scope of Claims] 1. An electrostatic recording medium whose surface is formed of an insulating layer and which is provided rotatably; A charging means for charging an electrostatic recording medium to a first polarity, comprising a plurality of needle-like electrodes, and forming an electrostatic latent image on a second polarity opposite to the charging potential of the electrostatic recording medium charged by the charging means. an electrostatic recording head that applies a recording voltage to form a charge image of a first polarity; a magnetic toner developing means for developing an electrostatic latent image charged with a second polarity remaining by the neutralizing means with a magnetic toner; an electrostatic transfer means for transferring an electrostatic recording medium onto a transfer medium, the neutralizing means being located between the electrostatic recording head and the magnetic toner developing means;
Electrostatic recording device. 2. The electrostatic recording device according to claim 1, wherein the neutralizing means neutralizes the first polarity charge image by corona discharge. 3. The neutralizing means includes: a mesh electrode facing the electrostatic recording medium; a corona wire that causes corona discharge between the mesh electrode and the corona wire in response to application of a voltage; 3. The electrostatic recording apparatus according to claim 2, further comprising power supply means for supplying voltage.