JPS60158473A - Developing method - Google Patents

Abstract

PURPOSE:To prevent adverse influence by a magnetic carrier and to perform development to high density by scattering a developer by a magnetic member on the outside circumference of a non-magnetic sleeve and generating powder smoke by the toner separated from the carrier of the two-component type developer. CONSTITUTION:The magnetic brush of a two-component type developer 9 formed to a non-magnetic sleeve 10a by a magnet roll 10 is forced to scatter from one end to the other end of a magnetic member 15 provided to the sleeve 10a. The chain bond of the magnetic carriers 9a of the developer 9 is released by such scattering by which the powder smoke consisting of the toner 9b alone is generated and the latent image on a recording drum is developed. The adverse influence by the magnetic carrier is prevented and the high-density development is executed by such constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a developing method for converting a latent image into a visible image in electrophotography, electrostatic recording, or the like.

[Background of the invention]

In electrophotography, electrostatic recording, etc., the developer that develops the electrical latent image formed on the recording medium is a one-component developer made of magnetic toner, in which the toner itself is magnetic, and a one-component developer made of magnetic carrier and non-magnetic carrier. There are two-part developers mixed with magnetic toner. In general, the developing device uses a cylindrical non-magnetic sleeve and a magnetic roll provided in the non-magnetic sleeve to attract the developer to the surface of the developing roll using the magnetic force of the magnetic roll, and the developer is hidden by the developer. There is one that rubs the surface of a recording medium that has an image to form a latent image, which becomes a visible image (toner image). In this developing method, the surface of the recording medium is rubbed with the developer layer adsorbed on the developing roll, so unless the thickness of the developer layer is regulated with high precision, an appropriate rubbing condition cannot be obtained. No visible image is obtained. Additionally, if the developer is conveyed at a high speed in an attempt to increase the development speed, the rubbing force becomes excessive, making it difficult for the toner to adhere to the recording medium, or the toner that has once adhered to the recording medium may be scraped off, causing the visible image to deteriorate. The disadvantage is that the concentration decreases.

In order to eliminate such drawbacks, in a developing method using an l-component developer, as disclosed in Japanese Patent Laid-Open No. 58-95369, magnetic toner flying from a developing roll acts on a recording medium to develop it. A non-contact developing method has been proposed.

However, when this non-contact development method is applied to development using a two-component developer, relatively large particle-sized magnetic carriers act on the surface of the recording medium, causing damage to the photoconductive photoreceptor layer or adhesion to the latent image. It has been found that satisfactory developing characteristics cannot be obtained because the toner is scraped off.

In addition, in each of the above-mentioned developing methods, the action of scraping off the toner once attached to the latent image is the effect of scraping off the toner that has once adhered to the latent image. The problem is that the color mixture is mixed into the developing device located at the rear, resulting in color mixture.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing method that can develop a latent image formed on a recording medium to a high density using a two-component developer consisting of a magnetic carrier and a toner while preventing the adverse effects of the magnetic carrier.

[Summary of the invention]

In order to achieve the above object, the present invention provides a developing method using a 52-component developer, in which a magnetic member provided along the outer periphery of a non-magnetic sleeve is magnetized by the magnetic force of a magnetic roll rotating inside the non-magnetic sleeve. As a result, the two-component developer conveyed around the outer circumference of the non-magnetic sleeve is caused to fly, and when this developer flies, the toner is separated from the magnetic carrier to generate toner powder smoke, and the latent image formed on the recording medium is By developing with toner powder smoke, it is possible to achieve high precision using toner while preventing the adverse effects of flying magnetic carriers.

[Embodiments of the invention]

FIG. 1 is a schematic diagram of a two-color printing laser beam printer showing an example of application of the method of the present invention. A photoconductive recording drum having a selenium photoconductor layer formed on the outer peripheral surface of an aluminum base rotates in the direction of arrow (A).

The outer peripheral surface of this photoconductive recording drum 1 is as follows.

It is uniformly charged by a charger 2 and then exposed to a first laser beam 3 to form a first electrostatic latent image. This first electrostatic latent image is a negative latent image in which the charge in the portion to which toner is to be attached has disappeared.

The first developing device R4 has a built-in first two-component developer 5 which is a mixture of black toner and a magnetic carrier. A layer (magnetic brush) is formed on the photoconductive recording drum by reversing the first electrostatic latent image (adhering a black 1-toner to the portion where the charge has disappeared) using a non-contact development method to be described later. A black toner image is formed on the surface of 1. Next, the unexposed area on the outer peripheral surface of the photoconductive recording drum 1 is exposed to a second laser beam A.
x7 to form a second electrostatic latent image. This second electrostatic latent image may be either a negative latent image or a positive latent image,
The second developing device 8 develops the image. The second developing device 8 contains a second two-component developer 9 containing a mixture of red toner and magnetic carrier, and this second developer 9 is attracted to a developing roll 10 to form a magnetic brush. A red toner image is formed on the surface of the photoconductive recording drum 1 by performing reversal development or normal development of the second electrostatic latent image using a non-contact development method to be described later. The two-color toner image thus formed on the outer peripheral surface of the photoconductive recording drum l is transferred onto the recording paper 11. After the transfer, the residual toner remaining on the outer peripheral surface of the photoconductive recording drum 1 is removed by a cleaner 12, and the residual charge is erased by uniform cod light from an erase lamp 13.

The present invention is a developing method suitable for such first and/or second developing devices 4 and 8, and will first be described in detail by taking as an example the case of second developing device M8, which is largely affected by color mixing.

FIG. 2 shows an example of the second developing section N8 for carrying out the developing method of the present invention. The developing roll 10 is a fixed sleeve 1 formed in a cylindrical shape from a non-magnetic material such as aluminum.
0a, and a magnetic roll ]Oc'' provided inside the non-magnetic sleeve log so as to rotate in the direction of arrow (b) about an axis 10b.The two-component developer 9 is a magnetic carrier 9a and a black roller. The toners 9b are mixed together and are charged to opposite polarities as they rub against each other, and the toners 9b adhere to the periphery of the magnetic carrier 9a by electrostatic force.

The magnetic roll 10c has an outer circumferential surface that has N poles periodically in the circumferential direction,
It is magnetized to have S pole, N pole...
The magnetic force attracts the developer 9 to the outer circumferential surface of the non-magnetic sleeve 10a, and the developer 9 forms a magnetic brush.

When the magnetic roll loc is rotated in the direction of the arrow (B), the magnetic brush moves the outer peripheral surface of the non-magnetic sleeve 10a in the direction opposite to the arrow (B).
conveyed in the direction.

The doctor blade 14 regulates the thickness of the magnetic brush conveyed on the outer peripheral surface of the non-magnetic sleeve 10a. A region adjacent to the photoconductive recording drum 1 and the non-magnetic sleeve 1Oa is a developing section, and an elongated plate-shaped magnetic member 15 is provided on the outer peripheral surface of the non-magnetic sleeve 10a of the developing section over the entire length in the axial direction. The magnetic member 15 has a width in the circumferential direction that is approximately equal to the magnetic pole spacing of the magnetic roll 10c, and is magnetized in the circumferential direction by the magnetic force of the magnetic roll lOc.

In the above configuration, during operation of the laser beam printer, the photoconductive recording drum 1 and the magnetic roll 10c rotate in the directions of arrows (A) and (B), respectively, and the developer 9 moves along the outer peripheral surface of the non-magnetic sleeve 10a. It is transported in the opposite direction to (b). The developer 9 that has reached the circumferential side end of the magnetic member 15 flies out from this side end in the direction of the photoconductive recording drum 1 and flies along the magnetic force line φ1 generated from the magnetic member 15. Although the reason for the phenomenon in which the developer 9 flies from the side edge of the magnetic member 15 is not clear,
The developer 9 until it reaches the side end of the magnetic member 15 is magnetized and strongly restrained by the lines of magnetic force φ2 of the magnetic roll 10c, whereas the side end of the magnetic member 15 is alternately magnetized as the magnetic roll lOc rotates. This is thought to be due to the repulsive magnetic field being applied to the developer 9.

The developer 9 generates powder smoke of the toner 9b when flying. In a state where the developer 9 forms a magnetic brush, the magnetic carriers 98 are combined by magnetic force to form a chain state, and the toner 9b
are these magnetic carriers9.

8 or mechanically confined between a plurality of magnetic carriers 98. However, during flight, the bonds between the magnetic carriers 9a are broken and they become dispersed, so the toner 9a that had previously been attached to a plurality of magnetic carriers 9a and the mechanical particles between the plurality of magnetic carriers 9a The toner 9b that was trapped in the magnetic carrier 98 is released and becomes free, and the electric field of the latent image easily acts on the toner 9b attached to the dispersed magnetic carrier 98, and the toner 9a is removed from the latent image. It is thought that the toner 9a separates from the magnetic carrier 9a and powder smoke is generated due to an increase in the electrostatic attraction force acting on the magnetic carrier 9a.

In the developing section, the powder smoke of the toner 9b acts on the surface of the photoconductive recording drum 1 to develop a latent image.

When reversing a negative latent image, the magnetic carrier 9a is used so that the toner 9b has a frictional charge of the same polarity as the latent image charge.
and the material of the toner 9b. When a positive latent image is normally developed, the material is set so that the toner 9b is triboelectrically charged to a polarity opposite to that of the latent image.

Incidentally, the concentration of the toner powder smoke generated from the developer 9 in the developing section is proportional to the conveyance amount of the developer 9, and can be reduced by reducing the particle size of the magnetic carrier 9a and increasing the toner mixing ratio in the developer. It increases. The particle size of the magnetic carrier 9a is preferably 20 to 60 μm, and the mixing ratio is preferably 10 to 30% by weight.

Further, the flying height of the developer 9 flying along the magnetic force line φ1 generated from the magnetic member 15 becomes lower as the rotational speed of the magnetic roll 10c becomes higher. Therefore, in order to increase the developing performance by bringing the outer peripheral surface of the photoconductive recording drum l closer to the outer peripheral surface of the non-magnetic sleeve 10a to narrow the gap between the two, it is necessary to prevent the developer 9 from flying away due to the centrifugal force received during conveyance. It is better to make the rotational speed of the magnetic roll 10c as fast as possible within the range.

According to experiments, a non-magnetic sleeve 1 with an outer diameter of 32 mm
Using an 8-pole magnetic roll 10c with a magnetic flux density of 800 Gauss on the outer peripheral surface of 0a, a thickness of 0.5 m and a width of 10
A magnetic member 15 made of n+m steel is installed, a developer 9 containing 25% by weight of toner-9b in a magnetic carrier 9a with an average particle diameter of about 30 μm is used, and a magnetic roll 10c is installed.
7n+m from the non-magnetic sleeve lOa due to the powder smoke of the toner 9b generated by rotating the
A positive latent image formed at a surface potential of 700 μ on a photoconductive (selenium) recording drum 1 that rotates at a peripheral speed of 8 cm/s is regularly developed to obtain a high-precision and good toner image. It was done. In this development, the developer 9 (sometimes the magnetic carrier 9a) flying along the magnetic line of force φ1 does not directly act on the latent image surface, so the toner adhering to the latent image is not scraped off and the effect of preventing color mixture is obtained. Moreover, the effect of preventing damage to the surface of the photoconductive recording drum 1 was also obtained.

FIG. 3 shows another example of a developing device for carrying out the method of the present invention. In this example, the latent images (A) and (G) are reversely developed, so for example, the first
It is suitable for the developing device 4. In this case, the difference from the developing device 8 shown in FIG.
A bias voltage in which a positive DC voltage and an AC voltage are superimposed is applied by 9, and the toner 5b is applied so that the latent image formed on the surface of the photoconductive recording drum 1 is negative and the developing device 4 performs reversal development. is charged with the same polarity as the latent image charge.

The voltage generated by the DC power supply 18 of this developing device 4 is 800V,
The voltage generated by the AC power supply 19 was set to 300 V at 800 Hz, and other conditions were the same as in the above embodiment, and a negative latent image formed on the photoconductive recording drum 1 having a surface potential of 1700 V was developed. A toner image was obtained. In this development, the DC bias current acts to overcome the repulsion of the positively charged toner 5b due to the electric field created by the positive charges on the photoconductive recording drum l, and causes the toner 5b to adhere to the latent image. . The alternating current bias voltage acts to facilitate separation of toner 5b from magnetic carrier 5a by its oscillating electric field, increase toner powder smoke concentration, improve development efficiency, and reduce fog (background stain).

The configuration of this developing device 4 can also be applied to the second developing device 8 of the laser beam printer shown in FIG. 1, and is effective in obtaining clear two-color toner images.

FIG. 4 shows yet another example of a developing device for carrying out the method of the present invention. In this example, collision plates 20 and 21 are added to the structure of the developing device 4 shown in FIG. 3. The developer 5 flies off from the side edge of the magnetic member 17, first collides with the first collision plate 2o, changes direction and travels approximately parallel to the surface of the photoconductive recording drum 1, and then reaches the 'C-th. 2 collision plate 2
1 and changes direction toward the non-magnetic sleeve 6a,
Return to the other side end of the magnetic member 17.

According to this developing device 4, the developer 5 passes through the collision plate 20 while flying through the space of the developing section where the bias electric field is applied. ．． 21
Since the toner 5b collides with the magnetic carrier 5a, the toner 5b is more effectively separated from the magnetic carrier 5a, and a higher concentration of toner powder smoke is generated, thereby improving the developing performance.

FIG. 5 shows still another example of a developing device for carrying out the method of the invention. In this example, the developing section shown in Fig. 4 is
4, the magnetic member 17 is inserted into the non-magnetic sleeve 6a.
The non-magnetic sleeve 6a is rotated in the direction of the arrow by attaching it to another stationary member without fixing it to the magnetic roll 6c. The developer transport by the non-magnetic sleeve 6a acts synergistically on the developer 5, increasing the transport speed of the developer 5. As a result, the amount of developer 5 flying from the side end of the magnetic member 17 in the developing section is reduced. This increases the density of the toner powder smoke, which ultimately improves the developing performance.

According to the experimental results, in the case of the developing section @4 shown in FIG. 4, the peripheral speed of the outer circumferential surface of the photoconductive recording drum l to be developed was 8 cm/s, and the image density of the solid black area was 1.5 cm/s. When the peripheral speed of 1 is increased to 15 cm/s, the image density becomes 0.
It dropped to 68. On the other hand, in the example shown in FIG. 5, by rotating the non-magnetic sleeve 6a by 5 Orpm, the
It was possible to develop an electrostatic latent image on the photoconductive recording tram l rotating at a circumferential speed of s to a density of 1.2.

Figure 6 shows the moving speed v (cm/s) of the recording medium being developed.
and the amount of toner adsorbed to the recording medium M (mg/cm2)
It is a characteristic that shows the relationship between This characteristic is achieved by using a 3 x 5 cm aluminum flat plate instead of forming an electrostatic latent image on the photoconductive recording drum 1, applying a voltage of 1,700 V to this flat plate, and developing the developing device 4 shown in FIG. , when the non-magnetic sleeve 6a and the magnetic member 17 are grounded. With the distance between the surface of the non-magnetic sleeve 6a and the aluminum flat plate (development gap) set to 10 mm and the rotation speed of the magnetic roll 6C set to 130 Orpm, the development characteristics are A when the rotation speed of the non-magnetic sleeve 6a is Orpm.
, the development characteristics are B when the rotation speed is 5 orpm, and the development characteristics are C when the rotation speed is 10 orpm.

The magnetic force and number of magnetic poles of the magnetic roll 6c, the outer diameter of the non-magnetic sleeve 6a, and the developer are the same as those of the developing device explained in FIG.

From this characteristic, it can be understood that by rotating the non-magnetic sleeve 6a, the amount of toner adhering to the aluminum flat plate is increased, and therefore, the developing speed can be increased by rotating the non-magnetic sleeve 6a.

The magnetic members on each side of FIGS. 2 to 4 described above can be embedded in a non-magnetic sleeve or deposited on the sleeve surface by vapor deposition or the like to produce an integrated structure with the same effect.

〔Effect of the invention〕

As described above, the present invention provides a developing method using a two-component developer, in which a magnetic part provided along the outer periphery of a non-magnetic sleeve is magnetized by the magnetic force of a magnetic roll rotating inside the non-magnetic sleeve. The two-component developer that is conveyed around the outer circumference of the magnetic sleeve is made to fly, and when this developer flies, the toner is separated from the magnetic carrier to generate toner powder smoke.
Since the latent image formed on the recording medium is developed with this toner powder smoke, it is possible to realize high-density development without being adversely affected by flying magnetic carriers.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a laser beam printer to which the method of the present invention is applied, FIGS. 2 to 5 are longitudinal sectional side views of the developing section thereof, and FIG. 6 is a development characteristic diagram. DESCRIPTION OF SYMBOLS 1... Photoconductive recording drum, 4... Developing device, 5... Two-component developer, 5a, 9a...
...magnetic carrier, 5b, 9b...toner, 6. Process 0...Development, roll, 6a, 10a...
...Non-magnetic sleeve, 6c. 10c...Magnetic roll, 15.17...
・Magnetic member. 1 Figure 3 Figure 3 Figure 4 Figure 5 Figure 6 V (cm/s)

Claims (1)

[Scope of Claims] 1. A magnetic roll is rotated within a cylindrical non-magnetic sleeve, and a layer of developer attracted to the outer peripheral surface of the non-magnetic sleeve by the magnetic force of the magnetic roll is developed at least by the rotation of the magnetic roll. The latent image formed on the recording medium is conveyed to a developing position, and the developer is flown from one side end to the other side end of a magnetic member provided along the outer periphery of the non-magnetic sleeve at this development position. In this developing method using a flying developer, a two-component developer in which a magnetic carrier and a toner are mixed is used as the developer, and when the developer flies, the toner is separated from the magnetic carrier and toner powder smoke is generated. and developing the latent image with the toner powder smoke. 2. In claim 1, a collision member is provided in the flight path of the two-component developer to collide the two-component developer in flight, and this collision promotes separation of the toner from the magnetic carrier. A developing method characterized by: 3. The developing method according to claim 1, wherein the two-component developer uses a magnetic carrier having a particle size of 20 to 60 μm, and the toner mixing ratio is 10 to 30% by weight.