JPS6161107B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an electrophotographic device or an electrostatic recording device in which an electrostatic latent image formed on a photoreceptor or dielectric material can be formed using a one-component developer consisting only of powder toner. The present invention relates to an electrostatic latent image developing device that visualizes an electrostatic latent image.

During development, colored fine powder called toner is charged with the opposite polarity to that forming the electrostatic latent image.
This is done by being electrostatically attracted to an electrostatic latent image. In addition to single-component developers consisting only of powdered toner, there are two-component developers consisting of a mixture of powdered toner and magnetic powder called carrier, or fine powder of resin, glass, etc. . In a two-component developer, the toner is charged by friction with the carrier, and the toner is reliably charged. On the other hand, in order to maintain a constant development density, the mixing ratio of toner and carrier, that is, the toner concentration must always be maintained constant. One-component developers consisting only of toner do not require such management of toner concentration, but require special measures to charge the toner, but they are easier to handle than two-component developers, so they have recently been developed. It is becoming more and more used.

One-component developers are classified into insulative and conductive, and below that, non-magnetic and magnetic. Non-magnetic toner is generally a mixture of resin powder and a coloring agent such as carbon, and magnetic toner is a mixture of resin powder and magnetic powder.

Conventional general developing devices using insulating toner charge the toner by frictional charging using a blade. The insulating toner supplied from the developer container is adsorbed onto the rotating conductive rubber surface, and the tip of the blade is brought close to or in pressure contact with the rubber surface to regulate the layer thickness of the toner on the rubber surface and to remove the toner. Triboelectrically charge. The charged toner comes into contact with the latent image on the carrier at a position where the rubber surface and the latent image carrier are close to develop it.

In this case, the charging polarity of the toner is determined by the material of the resin constituting the toner and the material of the blade. If the material of the toner is higher than the material of the blade in the triboelectric charging order, the toner will be positively charged, and if the opposite is the case, the toner will be negatively charged. The material of the blade is generally selected from resins such as Teflon and Delrin.

However, when toner is tribo-electrified by such a blade, the rise of the charging potential is slow;
The charging polarity and potential of the toner are uniquely determined by the toner used and the material of the blade, so there is no margin for error, and if used for a long time, the blade will wear out and the charging efficiency will decrease, etc. There are drawbacks.

The first feature of the present invention is to reduce the charging of the one-component developer supplied onto the conductive developer supply member by the electric charge from a conductive doctor blade provided in close proximity to or in pressure contact with the surface of the developer supply member. This is done by injecting The conductive doctor blade simultaneously regulates the layer thickness of the developer on the developer donor member and charges the developer.

The second feature of this invention lies in the shape of the conductive doctor blade. As described above, this conductive blade must simultaneously regulate the layer thickness of the developer and charge the developer. For this reason, it is important to ensure that a sufficient amount of charge can be imparted to the developer and that the appropriate thickness (approx.
30 μm to 60 μm) developer layer can be formed;
It must satisfy conditions such as not changing its shape even if slightly worn, and not applying excessive force to the developer to cause it to coagulate or solidify. The blade used in this invention satisfies these conditions.

According to the present invention, since the developer is efficiently and sufficiently charged, it is possible to obtain an excellent image with sufficient reproducibility even in a low-contrast image without background stains. In addition, the structure of the device is simple,
A small and inexpensive developing device can be provided.

Accordingly, it is an object of this invention to provide an improved electrostatic latent image development apparatus that uses a one-component powder developer.

A further object of the invention is to provide such an apparatus for charging the developer by charge injection from a conductive doctor blade.

A further object of the present invention is to provide the above-mentioned device in which the role of the conductive doctor blade, regulating the layer thickness of the developer and charging, can be sufficiently performed by devising the shape of the conductive doctor blade. It is in.

Other objects and features of the invention will become apparent from the following description with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of the present invention. The developing roller 1 serving as a developer supplying member is electrically conductive and has a volume resistivity of 10 ⁸ Ωcm or less, preferably 10 ⁵ Ωcm or less. The material may be entirely metal, but a core bar coated with graphite-mixed silicone rubber, chloroprene rubber, polyurethane rubber, etc. is effective in adsorbing and transporting the developer. These rubber materials have appropriate elasticity and are useful for easily forming a developer layer of an appropriate thickness on the surface. The developing roller 1 can also have a multilayer structure in which an elastic body is provided on a core bar, and a thin layer with relatively high hardness is provided thereon. Further, its shape is not limited to a roller shape, but may be a belt shape.

The developing roller 1 rotates counterclockwise, and the surface of the developing roller 1 has a portion extending from the bottom to the top.
A cover 2 is provided along the circumferential surface. The upper part of the cover 2 is bent outward and forms one side wall 4 of the developer container 3. The other side wall of the developer container 3 is replaced by a blade device 5. The blade device 5 includes a metal doctor blade 6.
and an insulating halter 7 that guides and holds it.
A conductive guide rod 8 fixed to the rear end of the blade 6
It consists of an insulating bracket 9 that guides the blade and holds the holder 7, and a compression coil spring 10 that is inserted into the guide rod 8 between the rear end of the blade 6 and the bracket 9. The blade device 5 maintains its positional relationship with the developing roller 1 by attaching a bracket 9 to the developing device main body. The tip of the blade 6 is pressed against the surface of the developing roller 1 with a constant pressure because the entire blade is pressed toward the developing roller 1 by a spring 10. A resistor 11 and a variable power supply 12 for charging are connected in series to the ground through a conductive guide rod 8 to the metal blade 6 . Further, a variable power source 13 for bias development is connected between the developing roller 1 and the ground. The resistor 11 is a protective resistor for preventing excessive current from flowing when the blade and the developing roller come into direct contact without using the developer.
This means that the developing roller is to some extent, e.g. 10 ⁵
Not necessary if the resistance is Ωcm or more.

The developer container 3 contains toner 14, which is a one-component developer. The toner in this example has a volume resistivity of 10 ⁹ Ωcm or more, preferably 10 ¹⁴
It is an insulating non-magnetic toner with a resistance of Ωcm or more. this is,
The main component is epoxy, styrene, phenol, or other resin, and contains dyes such as carbon and additives, such as zinc stearate and molybdenum disulfide to improve fluidity.

The toner 14 in the developer container 3 is affected by the surface energy of the developing roller surface, the cohesive force of the toners,
The toner applied later adheres to the surface of the developing roller due to electrostatic force between the developing roller and the like, and is transported by the counterclockwise rotation of the developing roller 1. The tip of the blade 6 is lightly pressed against the surface of the developing roller 1 by the constant force of the spring 10, but since the developing roller surface has elasticity, some of the toner on the roller surface passes through the tip of the blade. , transported in a uniform thin layer. Therefore, the thickness of the toner layer on the developing roller can be regulated by the degree to which the blade is brought into pressure contact with the developing roller surface. Further, when the toner passes through the tip of the blade, electric charge is exchanged between the blade and the developing roller via the toner, and the toner is injected with electric charge and charged.

When charging the toner 14 positively, the power supplies 12 and 13 are connected so that the blade 6 side is positive and the developing roller 1 side is negative. Conversely, when charging the toner negatively, the respective power supplies are connected so that the blade 6 side is negative and the developing roller 1 side is positive. However, toner 14
is charged even if potentials of the same polarity are applied to the blade 6 and the developing roller 1. The charging polarity of the toner at this time is determined by the direction of the electric field between the blade and the developing roller. That is, even if the potential is the same, if the potential applied to the blade 6 is higher than that of the developing roller, the toner will be positively charged, and if it is lower, the toner will be negatively charged.

The layer thickness is regulated by the blade 6, and the charged toner on the developing roller comes into contact with the electrostatic latent image on the photoreceptor surface 15 moving in the direction of the arrow below the developing roller, and develops it. When the electrostatic latent image is formed with negative charges, it is developed with positively charged toner, and when the latent image is formed with positive charges, it is developed with negatively charged toner. Develop it with When performing reversal development, toner of the same polarity as the latent image is applied. At this time, the developing roller 1 functions as a bias developing electrode to prevent background staining. That is, the developing roller 1
Then, a potential with the same polarity as the background potential of the electrostatic latent image or slightly higher is applied from the power source 13 to attract the toner that is about to adhere to the background part of the latent image to the developing roller surface, and to remove the latent image. Prevents development of the background area.

In this embodiment, if a current flows between the blade 6 and the developing roller 1 even when the development is stopped, that is, when the developing roller 1 has stopped rotating, the blade tip and the surface of the developing roller opposite thereto may Durable heat is generated in the toner between the two, which may cause the toner to melt and adhere to the tip of the blade or the surface of the developing roller. Therefore,
It is preferable to provide a switch between the blade 6 and the charging power source 12 so that the blade voltage is not applied when the developing roller 1 stops rotating.
Then, it is preferable to turn this switch on and off in conjunction with the rotation and stop of the developing roller 1.
Similarly, it is preferable to provide a switch between the developing roller 1 and the bias power source 13, and turn it on and off in conjunction with the rotation and stop of the developing roller.

Further, the charging potential of the toner charged by the blade 6 is determined by the magnitude of the potential applied thereto. Therefore, when developing a low-contrast electrostatic latent image, that is, an electrostatic latent image in which the potential of the image area is low and the potential difference between the image area and the non-image area is low, the voltage of the charging power source 12 is increased; Development is performed using toner with a high charging potential. In this case, the voltage of the bias power source 13 is also increased in conjunction with the charging power source 12. When the charged potential of toner increases,
This is to prevent toner from adhering to non-image areas of the latent image, thereby preventing background stains. In addition, changing the voltages of the charging power source 12 and the bias power source 13 can also be used to adjust the density and gradation of the developed image.

Next, the shape of the blade and its arrangement, which is the second feature of this invention, will be described. The blade in this invention has both the role of regulating the layer thickness of the toner and the role of charging the toner by passing a current through it. For this reason, the blade in this invention must have at least wear-resistant and electrically conductive properties. A material that satisfies this requirement is metal. However, metal materials have a higher coefficient of friction than resin materials used in conventional blades. For example, the coefficient of friction for steel is Teflon 0.04, Delrin 0.10, aluminum 0.36,
Brass is 0.46 and mild steel is 0.40. Therefore, even if the blade shape does not cause problems with a resin blade, if it is used as is in a metal blade, the fluidity of the toner will be inhibited due to the large coefficient of friction, which will cause the problem to occur on the developing roller. It may be impossible to obtain a sufficient amount of toner, or it may be inappropriate for charge injection by the blade.

As shown in FIG. 2, the shape of the blade according to the present invention is such that the outer shape of the cross section at the tip thereof is a flat side surface 6a on the side where the developing roller 1 enters.
A flat side surface on the side where the developing roller 1 advances and is parallel to the side surface 6a at a certain length l, and a side surface 6b perpendicular to these side surfaces 6a and 6b.
It is composed of an end plane 6c facing the surface of the developing roller. A slope 6d is continuously formed on the side surface 6b between it and the side surface 6e on the rear end side of the blade.

The width t of the end plane 6c, that is, the thickness of the tip of the blade, is suitably about 0.05 mm to 1.5 mm, and the thickness of the rear end of the blade is larger than this. If the width t of the end plane 6c is smaller than 0.05 mm, the toner layer 14a will not be sufficiently charged, resulting in a developed image with a dirty background. Furthermore, if the width t exceeds 1.5 mm, the toner layer 14a becomes thick, resulting in an image with a large amount of toner adhesion. In this case, if the pressing force of the blade 6 against the surface of the developing roller 1 is increased in an attempt to forcibly reduce the thickness of the toner layer 14a, the wear of the tip of the blade will be accelerated. The width t of the end plane 6c is
It is determined by the toner used and the material of the blade, the pressure force of the blade against the developing roller surface, the circumferential speed of the developing roller, the potential difference between the blade and the developing roller, etc., and the length l of the parallel part is determined by the strength maintained. It can be freely set up to 2mm as long as it is possible.

In the present invention, the blade having such a shape is arranged such that the side plane 6a on the side into which the developing roller surface enters is perpendicular to the direction of movement of the developing roller surface, that is, parallel to the axial direction of the developing roller. , so that it is substantially contained within a vertical plane, that is, within a normal plane. Then, the tip thereof is brought close to or in pressure contact with the surface of the developing roller as necessary.

In the blade device having such a configuration, the tip 6c of the blade that comes into contact with the toner layer 14a on the surface of the developing roller is flat.
It is possible to sufficiently contact the toner layer 14a and impart sufficient charge to the toner. Also,
Since the tip of the blade has the same cross section over a certain length l, the state of contact with the toner layer does not change even if it wears to some extent, and the charging state or developing state does not change. Furthermore, since the blade is arranged so that the side surface 6a of the blade on the side where the developing roller surface enters is substantially perpendicular to the developing roller surface along the axial direction of the developing roller, the tip of the blade can scrape off the surface. A toner layer of a required thickness can be formed without applying compressive force to the excess toner, and the state of contact of the blade with the surface of the moving developing roller can be maintained stably.

FIG. 3 is a schematic diagram showing another embodiment of the invention. Elements that are equivalent or have the same function as those used in the embodiment shown in FIG. 1 are given the same numbers. Particularly different from the embodiment shown in FIG. 1 are the structure of the developing roller 21 and the type of toner 22 used. The developing roller 21 is
It consists of a conductive non-magnetic sleeve 21a that rotates in a counterclockwise direction, and a bar magnet 21b that has a large number of magnetic poles on its circumferential surface and is statically housed inside the sleeve 21a. The conductive non-magnetic sleeve 21a is a non-magnetic sleeve coated with conductive rubber, and is connected to the bias power source 13. The sleeve itself is
It may be made of metal or resin as long as it is non-magnetic. The magnet housed in the sleeve may be a single bar magnet or a number of bar magnets arranged radially. In this configuration, it is also possible to keep the non-magnetic sleeve 21a stationary and rotate the bar magnet 21b clockwise.

The toner 22 contained in the developer container 3 is a magnetic toner. This toner is made by mixing magnetic powder such as triiron tetroxide into the non-magnetic toner used in the above embodiment, and has a volume resistivity of about 10 ⁹ Ωcm to ^{10 14} Ωcm. In order to avoid the influence of the magnetic force of the magnet in the sleeve, each member of the device is made of non-magnetic material. For example, the guide 2, container 3, and blade 6 are also made of non-magnetic material.

The magnetic toner 22 is attracted to the surface of the sleeve 21a by the magnetic force of the magnet 21b inside the sleeve. The magnetic toner on the sleeve is transferred to the sleeve 21a.
It is conveyed while being attached to the sleeve surface by the counterclockwise rotation of the sleeve. The sleeve becomes stationary;
In a device in which a magnet rotates, toner on a sleeve is transported by rolling on the sleeve in a direction opposite to the direction of rotation of the magnet. Toner 22 in the developer container
When leaving the developer container, the developer is charged by a blade device 5 having a configuration similar to that of the embodiment described above, and the amount of the adhesive is regulated. Then, in the same manner, the electrostatic latent image on the photoreceptor surface 15 is developed. In this embodiment, toner adsorption is better than in the previous embodiment.
This has the advantage of ensuring reliable transportation.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention;
FIG. 2 is a diagram showing the tip shape of a doctor blade used in the present invention, and FIG. 3 is a schematic diagram showing another embodiment of the present invention. 1: developing roller, 3: developer container, 5: blade device, 6: doctor blade, 14: one-component toner, 15: photoreceptor.

Claims (1)

[Scope of Claims] 1. A developer supplying member having an endless conductive surface that carries and moves a one-component developer consisting only of toner on its surface, and a developer that replenishes the developer to this developer supplying member. a container, a conductive doctor blade for regulating the layer thickness of the developer on the developer supply member and charging it, and the conductive doctor blade being brought close to or pressed against the developer supply member with a constant force. and a voltage applying means for applying a voltage between the developer donor member and the conductive blade, and the conductive doctor blade enters the surface of the developer donor member at its tip end. a flat side surface on the side, and a side surface parallel to the side surface at a certain length from which the developer-donor member surface extends;
The blade has an end plane perpendicular to these sides and facing the surface of the developer donor member, and the thickness of the tip of the blade is
The thickness of the blade is about 0.05 mm to 1.5 mm, and the thickness of the proximal end is larger than this. An electrostatic latent image developing device, characterized in that it is arranged so as to be substantially included in a vertical plane perpendicular to a direction crossing the .