JP2988543B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method in which a toner carrier carrying a developer is disposed on the surface of a photoreceptor and an exposure means is disposed on the back side of the photoreceptor, and the developer is rubbed on the surface of the photoreceptor. The present invention relates to an image forming method for forming an image while performing development almost simultaneously with exposure after charging.

[0002]

2. Description of the Related Art Conventionally, for example, a photosensitive drum formed by laminating a light transmitting conductive layer and a photoconductive layer on a light transmitting support,
Exposure means for generating a light output corresponding to the image information is interpolated, and the light output of the exposure means is converged to form a latent image on the photoconductor layer at the same time or immediately after that, and the photoconductor drum is opposed to the photosensitive drum. An image forming apparatus is known in which the latent image is converted into a visible image (toner image) via a toner carrier that has been made, and the toner image can be transferred to plain paper via a transfer roller or other transfer means. is there. (JP-A-58-15395)
No. 7, etc.)

In this type of image forming apparatus, in order to further simplify the structure and prevent ozone generation and the like, and to prevent ground fogging, the image forming apparatus faces the photosensitive drum without providing an independent charger. Along with carrying the conductive magnetic toner on the developing sleeve arranged as described above, a so-called magnetic brush-like developer rubbing area is provided immediately before the developing position by using a fixed magnetic pole or other magnetic force included in the sleeve, While the surface of the photosensitive drum was rubbed by the rubbing area, a charge was injected into the photoconductive layer of the drum through the rubbing area using a developing bias applied to the developing sleeve side. Then, immediately after the charging, an exposure image is formed and developed using an exposure head included in the drum, and a predetermined image is formed.

[0004]

Therefore, it is premised that the toner used in the above-mentioned apparatus is a conductive toner in order to inject electric charge from the developing sleeve side. As described above, it is not possible to employ an electrostatic transfer means by corona discharge. Therefore, generally, a transfer roller is used, and an electric force, heat, a magnetic force, or the like is applied to the transfer roller to increase transfer efficiency. However, the resistance value on the recording paper side is liable to fluctuate due to humidity and other environmental factors, so that stable and smooth transfer cannot be performed, and it is difficult to form high-quality images.

In order to solve such a drawback, a device using a two-component developer composed of a combination of an insulating toner and a conductive carrier (Japanese Patent Application Laid-Open No. 60-22145) has been proposed. In this case, resistance fluctuation is apt to occur due to the deterioration of the carrier, and the charging potential to the photosensitive drum side also fluctuates due to the resistance fluctuation, so that a stable image cannot be obtained with time. However, when the carrier deteriorates, it cannot be returned to the original state unless the carrier in the developing unit is replaced, which not only increases maintenance work and maintenance cost, but also effectively replaces only the carrier. Is impossible, and the replacement of the unit is forced, which is likely to cause a problem in resource saving.

SUMMARY OF THE INVENTION In view of the drawbacks of the prior art, an object of the present invention is to provide an image forming method capable of securing a stable charging potential and forming an image even if carrier deterioration occurs. It is another object of the present invention is to provide a simple image forming method capable of easily achieving the above object simply by supplementation career in developing container without the replacement of the developing unit.

[0007]

According to the present invention, when the conductive carrier is deteriorated, it is developed and consumed on the photosensitive drum side, and a new developer is always supplied to the rubbing area where the charging is performed. It was made. That is, the present invention is, developing
The developer carrier carrying the developer is exposed to the exposure
Steps are arranged on the back side of the photoconductor respectively, and at least the surface is
Is the carrier subjected to electroprocessing and high-resistance or insulating toner?
Rubbing the surface of the photoreceptor with the developer
And then charge it almost simultaneously with or
Image forming method for forming an image while performing development later
Consisting of a magnetic material dispersed in a binder resin
The conductive fine particles are fixed on the surface of the carrier base particles.
Using a carrier, fixed to the surface of the carrier base particles
Resistance increased due to peeling of conductive particles
Developed carrier with the toner on the surface of the photoreceptor
Consumption, and the carrier concentration changed by the consumption.
The degree or total amount is detected by a detection mechanism and the carrier is detected.
The image forming apparatus is characterized in that the image formation is performed while supplying the toner at appropriate times .

Therefore, it is assumed that a carrier whose resistance increases due to deterioration is used. For example, as shown in FIG. 4, a conductive material is applied to the surface of particles in which a magnetic substance 15 is dispersed in a binder resin 13 as shown in FIG. The conductive fine particles 17 are formed by fixing the conductive fine particles 17 so that the conductive fine particles 1 are deteriorated.
7 is peeled off and changes to a high resistance or insulating property similar to that of the toner, and can be attached to the photosensitive drum using the developing bias.

However, with the above construction, the number of carriers in the developing container is reduced, which hinders appropriate development. Therefore, in such a case, the present invention does not prompt the replacement of the developing unit itself as in the prior art, but detects the carrier concentration or the total amount reduced by the consumption by the detecting mechanism, and replenishes the carrier in a timely manner. Is a second feature.

In this case, it is necessary that the toner does not hinder image formation even when the toner is adhered to the photosensitive drum side. Therefore, at least the particle diameter of the carrier is adjusted.
For example, the diameter of the carrier may be set to 1 to 5 times the diameter of the toner, and the binder resin constituting the carrier may be colored in the same color or an approximate color as the toner.
It is an effective means.

As a result, the carrier has an increased resistance due to deterioration, and can be developed and consumed together with the toner on the photoconductor side. Further, since the developed carrier is adjusted in particle size, there is no problem in image formation.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Not just.

FIG. 1 is a schematic diagram showing the configuration of a printer according to an embodiment of the present invention. Reference numeral 1 denotes a photosensitive drum, which is formed by laminating a light-transmitting conductive layer 1b and a photoconductor layer 1c on a drum-shaped light-transmitting support 1a, and a developing sleeve described later as the light-transmitting conductive layer 1b. A developing bias is applied in between, and the motor can be rotated clockwise by a drive motor (not shown).

Next, the respective parts will be described in detail.
The translucent support 1a is made of a transparent inorganic material such as glass, quartz, sapphire, fluorine resin, polyester, polycarbonate, polyethylene, polyethylene terephthalate, or the like.
There are transparent resins such as vinylon, epoxy, and mylar, and they are formed in a drum shape.

The light-transmitting conductive layer 1b is made of a transparent conductive material such as ITO (indium tin oxide), lead oxide, indium oxide, copper iodide, or a metal such as AI, Ni or Au. It may be formed thin enough to be transparent.

The photoconductor layer 1c is made of a photoconductor made of a-Si: H. When the developing bias is positive, it contains a non-doped or Va group element in order to increase the electron mobility. When the bias is negative, a group IIIa element is preferably contained in order to increase the mobility of holes. Also, if necessary, to obtain desired characteristics such as electrical characteristics such as dark conductivity and photoconductivity, and optical band gap,
Elements such as C, O, and N may be contained. Further, the photoconductor layer 1c is formed of two layers, a photoexcitation layer region having a function of generating photocarriers from the back side and a layer region having a function of transporting carriers, thereby improving photosensitivity and withstand voltage. I can do it.

Reference numeral 2 denotes a developing device, which comprises a toner container 22, a container body 21 containing a carrier and toner, and includes a fixed magnet assembly 23 on the side of the container body 21 facing the photosensitive drum 1. The developing sleeve 20 is disposed and the sleeve 20 is opposite on the side facing the photosensitive drum 1.
Rotatably configured clockwise direction direction.

The toner container 22 and the container body 21 are separated by a partition wall 24. A supply roller 25 is disposed in a slit opening provided at the center of the partition wall 24. The supply roller 25 rotates each time the carrier / toner mixture ratio (developer concentration) decreases, so that the proper concentration ratio is always maintained.

A pair of mixers 27, such as magnet rolls, are disposed in the container body 21 to maintain a uniform carrier / toner mixture ratio in the container body 21. A doctor blade 28 is attached to the entrance end of the container 21 on the lower surface side of the developing sleeve 20 so that the developer guided to the developing position can be regulated to a thin layer. Next, the composition of the developer will be described.

FIG. 4 is a schematic view showing an embodiment of a carrier used in the developer of the present embodiment. The conductive fine particles 17 are formed on the surface of carrier base particles 13 in which a magnetic material 15 is uniformly dispersed in a binder resin. Are fixed to form the carrier 11.

The carrier 11 has a volume resistivity of 10 ^4.
Ω · cm or less, more preferably 1 Ω · cm or less.
0 ⁸ to 10 ⁴ · Ω · cm. If the volume resistivity is too large, the characteristics as a conductive carrier are impaired. For example, when used in a back exposure method, charge injection is not performed promptly, and the photoconductor becomes insufficiently charged. The conductivity of the carrier 11 is mainly given by the conductive fine particles 17.

The volume specific resistance of the carrier 11 was determined by placing 1.5 g of the carrier 11 in a Teflon cylindrical body having an inner diameter of 20 mm and having an electrode at the bottom, inserting an electrode having an outer diameter of 20 mm, and applying a load of 1 kg from the top. It is the value when measured.

The magnetic force of the carrier 11 needs to be larger than a certain level. Preferably, the maximum magnetization in a magnetic field of 5 KOe (Oersted) is 55 emu / g or more, more preferably 55 to 80 emu / g. Also, 1K
The maximum magnetization of the Oe in the magnetic field is preferably 45 emu / g or more, more preferably 45 to 60 emu / g.
When the magnetic force of the carrier 11 becomes too small, the transportability of the developer deteriorates, and the carrier 11 is developed together with the toner.

The average particle size of the carrier 11 is 1 to
It is good to set it to 5 times.
In the case of the average particle size, it is preferably from 10 to 50 μm, and more preferably from 15 to 25 μm. If the carrier 11 is too large, it becomes difficult not only to uniformly charge the photoconductor, but also to hinder image formation, and it is not possible to further increase the toner density. On the other hand, if it is too small, the transportability of the developer on the developing sleeve deteriorates, and it becomes difficult to apply a constant potential.

The true density of the carrier 11 is 3.0 to 3.0.
A range of 4.5 g / cm ³ is preferred. As a magnetic material,
Magnetite (Fe ₃ O ₄ ), ferrite (Fe
₂ O ₃ ) and the like are used, and magnetite is particularly preferable, but is not limited thereto.

As the conductive fine particles 17, carbon black, tin oxide, conductive titanium oxide (a titanium oxide coated with a conductive material), silicon carbide and the like are used, and the conductivity is increased by oxidation with oxygen in the air. Those that do not lose are desirable.

The binder resin used for the carrier base particles 13 is heat-fused by a fixing device in the same manner as a toner such as a vinyl resin represented by a polystyrene resin, a polyether resin, a nylon resin and a polyolefin resin. It is preferable to use a resin colored black like the toner.

To fix the conductive fine particles 17 to the surface of the carrier base particles 13, for example, the carrier base particles 13 and the conductive fine particles 17 are uniformly mixed, and the conductive fine particles 17 are adhered to the surface of the carrier base particles 13. After that, a mechanical and thermal impact force is applied to drive the conductive fine particles 17 into the carrier base particles 13 and fix them. The conductive fine particles 17 are not completely embedded in the carrier base particles 13, but are fixed so that a part thereof protrudes from the carrier base particles 13.

By fixing the conductive fine particles 17 on the surface of the carrier 11 as described above, the carrier 11 can be efficiently formed.
High conductivity. Further, the carrier base particles 13
Since it is not necessary to mix the conductive fine particles 17 therein, as many magnetic substances 15 can be compounded in the carrier base particles 13 and the magnetic force of the carrier 11 can be increased.

The carrier and the toner are mixed to form a developer. Normal average particle size of 5 to 10 μm as toner
m of an insulating toner is used, and preferably has a volume resistivity of 10 ¹⁴ Ω · cm or more, more preferably 10 ¹⁶ Ω · cm or more. This value is measured as in the case of the carrier.

The composition of the toner is the same as that of the conventional toner. For example, a binder resin, a coloring agent, a charge controlling agent, an offset preventing agent, and the like can be added.
Also, a magnetic substance can be added to form a magnetic toner,
This is effective for preventing toner from scattering inside the machine.

On the other hand, the developing sleeve 2
The exposure head 3 is fixedly arranged on the inner peripheral surface side of the drum 1 facing 0. The exposure head 3 is formed by an LED or EL head array 31 for generating an optical output corresponding to image information and a converging lens 32 (trade name: Selfoc lens), and the image forming position of the lens 32 is determined by the photosensitive drum 1. Slightly from the focal line connecting the axis of the developing sleeve 20 and the drum 1
It is configured to be deflected to the downstream side in the rotation direction to form an image on the photoconductor layer 1c in the drum 1.

In the figure, 4 is a transfer roller, 5 is a registration roller, and 6 is a paper detection sensor. The transfer roller 4 uses a conductive roller to increase the transfer efficiency, and applies a transfer bias having a polarity opposite to the charge potential of the toner.
The photosensitive drum 1 is uniformly pressed against the peripheral surface thereof, and is configured to be rotatable in synchronization with the drum 1. The transfer roller 4
As for the material, since the toner to be transferred is an insulating toner, it is not necessary to make the material particularly conductive, and it is also possible to make the material high resistance or insulating.

Next, a detection mechanism for detecting the carrier concentration (deterioration of carrier) on the developer rubbing area is arranged as shown in FIGS. FIG. 2 shows an example of a detection mechanism using a developing bias, and its configuration will be described in detail with reference to FIG. The developing bias Vi is formed by a DC voltage that is made constant by a constant voltage circuit (not shown), and the developing bias Vi flows to the developing sleeve 20, the developer rubbing area 10, and the photosensitive drum 1 side. The outlet side of the drum 1 is grounded via a voltage dividing resistor R1, and a detection voltage between the load and the voltage dividing resistor R1 is taken out to the detection circuit 50 side. In the detection circuit 50, the comparator 51
And the reference voltage setting circuit 52. When the detection voltage falls below the reference voltage, the comparator 51 can determine that the carrier concentration has decreased in the developer rubbing area 10. A signal is output to prompt the display unit 53 to replenish the carrier. FIG. 3 shows a configuration of a detection mechanism 60 using an optical sensor. That is, the developing area D1 defined by the developing sleeve is set to be larger than the width of the image forming area of the recording paper, in other words, larger than the exposure area D2, and the photoconductive layer of the photosensitive drum 1 is provided in the non-image area (D1-D2). A light emitting body 61 having a wavelength capable of transmitting light through the photosensitive drum 1c;
And a light receiving sensor 62 disposed at a position facing the light emitting body 61 with the interposed therebetween. In this case, since the photoconductive layer 1C is made of a-Si: H, light can be easily transmitted by setting the wavelength of the luminous body to, for example, 800 nm or more. According to the detection mechanism 60, while the conductive fine particles 17 adhering to the surface of the carrier 11 do not peel off and maintain the conductivity, the carrier does not adhere to the photosensitive drum 1 side, and Although the light from the sensor 61 can be received by the light receiving sensor 62, the conductive fine particles 17 attached to the surface of the carrier 11 are separated, and as the resistance increases, the carrier adheres to the photosensitive drum side.
The attached carrier blocks light from the light emitter, and the light receiving sensor 6
2, the amount of received light decreases. Then, when the amount of received light drops below a predetermined level, the detection circuit 63 detects this, and outputs a carrier supply signal from the detection circuit 63 to prompt the display section 64 to replenish the carrier.

Next, the operation of the embodiment will be described. First, when the power is turned on to perform an initial check and the printing operation is started, first, a drum motor (not shown) is turned on, and then a driving motor (not shown) on the developing device 2 side is turned on, and together with the mixer 27, When the developing sleeve 20 rotates, the toner concentration is checked by the sensor 26 at the same time. After the developer rubbing area 10 is formed between the developing sleeve 20 and the drum 1 by the rotation of the developing sleeve 20, based on the developing bias current flowing to the drum 1 side through the rubbing area 10, the detection shown in FIG. If the deterioration state of the carrier is detected by the circuit 50 and there is no problem, the exposure by the exposure head 3 is started at the same time as the sheet is fed from the registration roller 5 to perform the image forming operation.

The image forming operation is performed while the photosensitive drum 1 and the developing sleeve 20 are rotated in opposite directions to each other while the developing container 21 is rotated.
Drum 1 / sleeve 2 using the magnetic force of the fixed magnetic pole assembly 23 containing the developer conveyed in the sleeve 20.
A developer rubbing area is generated at an opposing position between 0. In this case, since the magnetic powder is contained in the carrier similarly to the toner, the carrier is smoothly held in the rubbing area.

In the rubbing area, charges are injected into the photoconductive layer 1c of the drum 1 through the carrier 11 mixed in the rubbing area using the developing bias applied to the developing sleeve 20 side. Immediately after the charging, an exposure image is formed using the exposure head 3 included in the drum 1 and toner is adhered to the exposed portion to perform development. When the developing force exceeding the magnetic force conductive particles 1 7 to the surface of the carrier core particles 13 is resistance to peeling is adsorbed to elevated sleeve 20 by friction the sliding occurs, the carrier 11 with the toner photosensitive Body drum 1
Adhesive development on the side and is consumed. It is configured to perform a predetermined image formation.

The carrier is always supplied from the side of the developing container 21 due to the consumption of the carrier 11, but when the carrier 11 is consumed to a certain extent, the carrier concentration in the rubbing region 10 is reduced. Since the detection circuit 50 performs a detection operation each time an image forming operation starts, when a supply signal is output from the detection circuit 50,
The image forming operation is interrupted, the toner container 22 is removed, and the carrier is supplied into the developing container 21. On the other hand, according to the detection mechanism 60 shown in FIG. 3, it is possible to always detect the deterioration of the carrier during the image forming operation, which is advantageous particularly in the case of performing continuous printing.

[0039]

As described above, according to the present invention, it is possible to secure a stable charging potential and to form an image even when carrier deterioration occurs, and simply replenish the carrier in the developing container without replacing the developing unit. The above object can be easily achieved simply by performing the following. And so on.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a cross-sectional configuration of a printer according to an embodiment of the present invention .

FIG. 2 is a first example diagram of a carrier concentration detection mechanism used in the printer of FIG.

FIG. 3 is a diagram illustrating a second example of a carrier concentration detection mechanism used in the printer of FIG. 1;

FIG. 4 is a composition diagram of a conductive carrier constituting a developer.
is there.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Developing means 3 Exposure means 10 Developer rubbing area 50, 63 Detection circuit 21 Developing container (container main body) 11 Carrier

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/05 G03G 15/06 101 G03G 15/08 G03G 15/09

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein a developer carrying member carrying the developer is exposed to light.
Exposure means are arranged on the back side of the photoconductor on the body surface side, respectively.
Carrier with at least surface conductive treatment and high resistance
Or a developer made of an insulating toner.
After charging while rubbing the photoreceptor surface, almost
Simultaneously or immediately after, image formation while developing
Image forming method to be performed,Carrier mother with magnetic material dispersed in binder resin
The carrier in which conductive fine particles are fixed on the surface of the particles
Use  The carrierThe conductive fine particles fixed on the surface of the mother particles
PeelingIncreased resistancedeteriorationA careerSaid
With tonerSaidPhotoconductorsurfaceAnd consume it for development
Changed by the consumptionCareerDetect concentration or total amount
Detected by the mechanism,The carrierWhile replenishing
An image forming method characterized by performing image formation. 2. A sets a diameter of the carrier 1 to 5 times the toner diameter, the toner of the same color Wakashi Ku
Is to use the binder resin colored to an approximate color.
The image forming method according to claim 1, wherein: