JPH03233477A - Developing device - Google Patents

Abstract

PURPOSE:To reduce the toner consumption and to improve the print quality by constituting developer conveyance members, a developer control means, and a developer so that the work functions of the developer conveyance members and developer control member are both larger or smaller than the work function of the developer. CONSTITUTION:The developer conveyance members 7 and 10, developer control means 8, and developer 4 are so constituted that (Wd-Wt) X (Wb-Wt) > 0, where Wd, Wb, and Wt are the work functions of the developer conveyance members 7 and 10, control means 8, and developer 4. Thus, the work functions Wb and Wd of the thickness layer control member 8 which charges the developer 4 electrostatically and the developer conveyance members 7 and 10 are both larger (in the case of negatively charged toner) or smaller (in the case of positively charged toner) than the work function Wt of toner to be charged electrostatically to equalize them in the polarity of triboelectric charge. Therefore, the toner is prevented from being charged electrostatically to the opposite polarity from desired polarity and much toner from being charged electrostatically to low potential. Consequently, the print quality is improved and the toner consumption is reduced.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Conventional technology (Figures 7 and 8) Means for solving the problem to be solved by the invention (1st diagram of action) Examples (a) Description of the first embodiment (Figures 2 to 4) (
b) Description of the second embodiment (Figures 5 and 6) (C)
Description of other embodiments Effects of the invention [Summary] Preventing the generation of reversely charged toner or lowly charged toner in a developing device that conveys a charged developer to an image bearing member on which an electrostatic latent image is formed to develop the image. The present invention aims to obtain a developer with uniform charging characteristics, and includes a developer, a developer transport member for transporting the developer, and a developer regulating means for regulating the layer thickness of the developer. , the developer is transported by the developer transporting member,
In a developing device that conveys and develops an image bearing member on which an electrostatic latent image is formed, the work functions of the developer conveying member, the developer regulating means, and the developer are expressed as Wd, Wb, and Wt, respectively.
The developer conveying member, the developer regulating means, and the developer were configured so as to satisfy the relationship (Wd-Wt)X (Wb-Wt)>0.

[Industrial application field]

The present invention relates to a developing device that conveys a charged developer to an image bearing member on which an electrostatic latent image is formed to develop the image.

In image forming devices such as electrophotographic devices and electrostatic recording devices,
Developing devices are widely used to visualize electrostatic latent images on photosensitive drums and dielectric materials that are latent image carriers.

Conventionally, such developing devices have been widely used using two-component developers consisting of carrier and toner, but in recent years, devices using single-component developers have also been introduced, which are easier to handle and make the device more compact. It's being used.

A developing device using such a developer is desired to be capable of supplying a stable charged toner and performing stable development over a long period of time.

[Conventional technology]

FIG. 7 is an explanatory diagram of the prior art.

For example, in the -component developing device 2a, a developing roller (developer carrier) 7 is provided with respect to a photosensitive drum (image carrier) 1 that rotates in the direction of the arrow.

The developing roller 7 carries the one-component non-magnetic toner 4 of the developing device 2a.
A rubber blade (developer blade) is provided upstream of the developing section to carry the toner layer uniformly over the entire length of the developing roller 7 and to charge the toner 4. A regulating member) 8 is provided in pressure contact with the developing roller 7.

The one-component developing device 2a is configured to press the charged toner of the developing roller 7 against the photosensitive drum 1 with a constant nip width in order to obtain the desired print density and print quality. It is made of an elastic material such as rubber or NBR rubber.

Note that 5 is an agitator that stirs the toner 4, and 9 is a collection roller that collects the toner 4 from the developing roller 7 and supplies new toner 4.

[Problem to be solved by the invention]

By the way, since the photosensitive drum 1 is inexpensive, for example, a PC photosensitive member is attracting attention, and the toner used therein is required to have negative polarity.

The charging mechanism when such a -component non-magnetic toner is used is thought to be due to frictional charging between the toner and the developing roller 7 and frictional charging between the toner and the blade 8.

Furthermore, in a two-component developer consisting of toner and carrier, it is thought that this is due to frictional charging between the toner and the carrier 7, and between the toner and the blade.

If, for example, polyester toner is used as the toner 4, urethane rubber is used as the developing roller 7, and rubber whose surface is coated with Teflon is used as the blade 8, the conventional toner charge distribution shown in FIG. As shown in the characteristic diagram, a large amount of positively charged toner opposite to the desired charging polarity and lowly charged toner were generated, and the resulting toner was non-uniformly charged.

Therefore, in addition to background fog caused by low-charge toner, positively-charged toner remains untransferred and is discarded.
A problem has arisen in that the amount of toner consumed increases.

Therefore, an object of the present invention is to provide a developing device that can prevent the generation of reversely charged toner or lowly charged toner and obtain a developer with uniform charging characteristics.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle of the present invention.

Claim (1) of the present invention, as shown in FIG. and a regulating means 8, in which the developer 4 is transported and developed by the developer transport member 7 onto the image carrier 1 on which an electrostatic latent image is formed, the developer transport member 7 and the developer regulating means 8
and the work functions of the developer 4 are Wd, Wb, and Wt, respectively.
When (Wd - W t ) X (Wb - W
The present invention is characterized in that the developer conveying member 7.10, the developer regulating means 8, and the developer 4 are configured so as to satisfy the relationship: t)>0.

In claim (2) of the present invention, the developer 4 is a one-component developer, and the developer transporting member 7.10 is a developer carrying member that transports the developer 4 in contact with the image carrier l. It is characterized by having a body of 7.

Claim (3) of the present invention is characterized in that in claim (1), the developer conveying member 7.10 is a carrier 10.

A fourth aspect of the present invention is characterized in that, in the first aspect, a voltage is applied to the developer regulating means 8 to forcibly charge the developer 4.

[Effect]

The present invention focused on the work function of each triboelectrically charged member 4.7.10.8.

The work function of a substance is the energy required to extract electrons from the substance, and the smaller the work function, the easier it is to extract electrons, and the larger the work function, the more difficult it is to extract electrons, and is related to the charge series.

Here, when examining the conventional combinations, for the work function Wt of the toner 4, the developing roller 7 made of polyurethane rubber.
The work function Wd of No. 10 is small, and the toner is charged to the desired polarity, but the work function wb of the rubber blade 8 on which Teflon is vapor-deposited is larger than the work function Wt of the toner, and the frictional charging with this rubber blade 8 is small. It was found that this weakens the charge on the toner or charges it to the opposite polarity.

Therefore, in the present invention, the work function w of the layer thickness regulating member 8 for charging the toner (developer) 4 and the developer conveying member 7.
By configuring b and Wd to be both large (in the case of negatively charged toner) or both small (in the case of positively charged toner) with respect to the work function Wt of the toner to be charged, the polarity of each triboelectric charge can be made the same. And so.

As a result, the effects of each frictional electrification overlap to obtain stable electrification, and a charged toner with the opposite polarity to the desired one or a large amount of low-charged toner is generated, causing background fog in the print and significantly deteriorating the print quality. It is possible to prevent problems such as increase in toner consumption.

〔Example〕

(a) Description of one embodiment FIG. 2 is a block diagram of a first embodiment of the present invention, and shows an example of a -component developing device.

In the figure, 1 is an OPC photosensitive drum with a diameter of 60 m.
m, the surface speed is 70 mm/s, and after the surface is charged to 1650 cm by a corona discharger (not shown), it is irradiated with light according to the information to be recorded by a laser scanning optical system, an LED exposure optical system, etc. An electrostatic latent image is formed by this process.

Reference numeral 2a denotes a development device having the following configuration in order to visualize an electrostatic latent image by supplying a one-component non-magnetic toner onto the OPC photosensitive drum 1.

That is, the developer container 3 stores mono-component non-magnetic toner 4 having an average particle size of about 10 μm, and the agitator 5 rotates in the direction of arrow A within the developer container 3 to remove the -component non-magnetic toner 4. is conveyed toward the paddle roller 6.

The paddle roller 6 is a first roller formed at the bottom of the developer container 3.
By rotating in the direction of arrow B, the one-component non-magnetic toner 4 present at the lowest position in the developer container 3 is pumped up and supplied in the direction of a developing roller 7, which will be described later.

The developing roller 7 rotates in the direction of arrow C and conveys the one-component non-magnetic toner 4 conveyed by the paddle roller 6 to the contact portion with the OPC photosensitive drum 1 while adsorbing it to its surface. This is to visualize the electrostatic latent image above.

The developing roller 7 has, for example, a diameter of 20 mm, a volume resistivity of 104 to 1010 Ω·m (optimally 10 6 Ω·m),
Hardness is 8 to 35° (Asker hardness: Optimally 100
) A single layer made of polymeric foamed polyurethane, which is an open-pore porous material, is formed around a metal central shaft, and a developing bias voltage (-300
V) is applied.

Furthermore, the developing roller 7 is applied with a linear pressure of 22 to 22 by pressing the entire developing container 3 in the direction of the OPC photosensitive drum 1 (in the direction of the arrow Y) by a biasing means such as a spring (not shown).
It is pressed at 50 g/cm (optimally 43 g/cm) and is pressed against the OPC photosensitive drum rotating in the direction of the arrow so that the nip width is 1 to 3.5 mm.

The blade 8 has an aluminum tank bottom and is rotatable around a shaft 8a, and applies a linear pressure of 26 g in the direction of arrow X to the developing roller 7 by a biasing means such as a spring (not shown).
/mm, which regulates the toner layer pressure on the developing roller 7 to a constant value and charges the toner to a desired polarity by frictional charging.

However, triboelectric charging is highly dependent on the environment, and the amount of charge on the toner changes with changes in the environment. In addition, variations in the initial potential may occur due to changes over time. Therefore, by applying a voltage to the blade 8 and injecting charge into the toner from the blur, the toner charge amount is controlled. It has been confirmed that control of ±1 μq/m is actually possible with a blade applied voltage of ±200 V.

The collection roller 9 has a volume resistivity of 10, similar to the developing roller 7.
@Ω·m1 It is a polymeric foamed polyurethane with a hardness of about 10 to 70°, and is arranged in the second recess 3b of the developer container 3. This collection roller 9 has a diameter of 11 mm and a circumferential speed of 7.
0mm/s, and the nip thickness is 1mm.
Furthermore, the developing bias voltage ~3 applied to the developing roller 7
By applying a collection bias voltage (-300V to -250V) equal to or larger than 00V, the single-component non-magnetic toner 4 which is mechanically and electrically negatively charged is collected from the surface of the developing roller 7. , is provided to eliminate mechanical and electrical history on the developing roller 7.

In the tank bottom described above, aluminum was used as the blade 8 in this example. In addition, the developing roller 7 has a 20' volume resistivity of 107Ω・c on the Asker-C hardness meter.
Foamed polyurethane (Manan product name: Rubicel, manufactured by Toyo Polymer Co., Ltd.) with a foamed pore size of 3 to 20 μm was used.

Toner 4 was a polyester toner. Toner 4 contains 93 parts by weight of a polyester resin (acid value: 45, melting point: 145°C) produced by condensation of terephthalic acid, trimetic acid, and a diol represented by structural formula (1), and 3 parts by weight of carbon (black). , Pearls L; Cabot Corporation), 1 part by weight of polypropylene wax (Viscol 550P; Sanyo Chemical), and 2 parts by weight of azo dye (Eisenspiron Black TRH, Hodogaya Chemical) were mixed, melted, and mixed, and the particle size was 5 to 15 μm. This is a polyester-based negative polarity toner produced by finely pulverizing the toner, and in this case, the work function of the toner was measured to be 5.35ev.

Here, RI is CnH, n 1≦n≦5 Fig. 8 is a work function relationship diagram of the first embodiment of the present invention, and Fig. 4 is a work function relationship diagram of the first embodiment of the present invention.
FIG. 3 is a graph of toner charging characteristics according to an embodiment of the present invention.

When the work function of the combination of the above examples was measured,
As shown in FIG. 3(B), the work function of the aluminum blade 8 is 4.41 eV, the work function of the polyurethane developing roller 7 is 4.49 eV, and the work function of the polyester toner 4 is 5.35 eV. smaller.

Therefore, both the blade 8 and the developing roller 7 charged the toner 4 to a negative polarity, and the good charge distribution characteristics shown in FIG. 4 were obtained.

The charge distribution characteristics shown in FIG. 4 were obtained by measurement using a surface analyzer (AC-1 manufactured by Riken Keiki).

In contrast, in the prior art, as shown in FIG. 3(A), the work function of the urethane rubber developing roller 7 is 4.49.
e v is smaller than the work function of toner, which is 5.35 e v, but the work function of the rubber blade 8 having Teflon formed on its surface is 5.75 e v, which is larger than the work function of toner.

For this reason, the developing roller 7 charges the toner 4 with negative polarity, but the blade 8 charges the toner with the opposite positive polarity.

Therefore, in the conventional technology, toner of opposite polarity and a large amount of low charge toner are generated as shown in FIG. 8, but in the present invention, toner of opposite polarity is not generated as shown in FIG. 4, and low charge toner is generated. The occurrence of this has also decreased significantly.

(b) Description of Second Embodiment FIG. 5 is a block diagram of a second embodiment of the present invention, showing an example of a two-component developing device.

In the figure, the same components as those shown in FIG. By supplying component developers, an electrostatic latent image is visualized, and has the following configuration.

That is, an agitator 5 that stirs the two-component developer, a magnetic roller (1) which has a magnet (llb) inside a rotating sleeve (lla) and supplies the two-component developer to the photosensitive drum (1), and the two-component developer on the magnetic roller (11). It has a doctor blade 8 that controls the layer thickness of the toner 4 and injects charge into the toner 4, and a toner hopper 12 that replenishes the toner 4.

In this two-component developing device, toner 4 is sucked by carrier 10, a magnetic brush is formed on sleeve lla, and two-component developer is supplied to photosensitive drum 1 by rotation of sleeve lla. It constitutes a developer conveying member that conveys the toner 4.

The toner 4 was charged by frictional charging between the toner 4 and the carrier 10 and by frictional charging between the doctor blade 8 and the toner 4 .

Similar to the first embodiment described above, in order to make both frictional charges the same polarity, the toner 4, carrier IO, and doctor blade 8
The work functions of are set to have the same relationship as in the first embodiment.

FIG. 6 is a work function relationship diagram of a second embodiment of the present invention,
FIG. 6(A) shows the conventional example, and FIG. 6(B) shows the case of the present invention.

In this embodiment, a styrene-based toner is used as the toner 4, fluorine-coated magnetite is used as the carrier 10, a conductive resin is used as the doctor blade 8, and a voltage is applied to the doctor blade 8 to inject charge into the toner 4. , charged.

When the work function of the combination of this example was measured,
As shown in FIG. 6(B), the work function of the carrier 10 is 6.0 Oev, and the work function of the doctor blade 8 is 6.2.
0ev, both of which are larger than the work function of Toner 4, which is 5.60ev.

Therefore, both the carrier 10 and the doctor blade 8 charge the toner 4 to a positive polarity.

When the toner charge distribution of this combination was measured, results similar to those shown in FIG. 4 were obtained.

On the other hand, in the conventional technology, as shown in FIG. 6(A), the work function of the styrene toner is 5.60 eV, and the work function of the magnetite carrier not coated with fluorine is 4.60 eV. The work function of the aluminum blade was 5.75 ev, which was smaller than the work function of the toner.

For this reason, the carrier charges the toner negatively, but the blade charges the toner positively, producing toner of the opposite polarity and a large amount of low-charge toner, as shown in Figure 8. In the invention, as shown in FIG. 4, toner of opposite polarity is not generated, and the generation of low-charge toner is greatly reduced.

(C) Description of other embodiments In the first embodiment described above, an example was explained in which the polyester toner (work function 5.35 ev) was negatively charged. However, in order to positively charge the polyester toner, the developing roller When a Teflon-coated rubber roller is used, the work function is 5.75 ev, and both the developing roller and blade have larger work functions than the toner, and the polyester toner can be positively charged.

Furthermore, although the toner has been described as a polyester-based toner, it may be applied to well-known non-magnetic toners such as styrene-based toners.

For example, styrene-acrylic resin manufactured by copolymerizing styrene and n-butyl acrylate (melting point: 140°C
) 90 parts by weight, 5 parts by weight of carbon (Black Pearls; Cabot Corporation), 3 parts by weight of polypropylene wax (Viscol 550P; Sanyo Chemical), 2 parts by weight of azo dye (Eisen Subiron Black TRH, Hodogaya Chemical).
This is a styrene-acrylic negative polarity toner manufactured by mixing, melting, cross-mixing, and finely pulverizing the particles to a particle size of 5 to 15 μm. In this case, the work function of the toner was measured to be 5°25 (
ev).

You may use this.

Furthermore, although charge injection by applying voltage to the blade 8 is effective for changing the environment, it is not necessary to perform this, and the image carrier is not limited to a photosensitive drum, but may be a dielectric material or the like.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, (1) the frictional charging of the developer by the developer transport member and the layer thickness regulating member can be made to have the same polarity, so generation of oppositely charged developer can be prevented, and toner This has the effect of significantly reducing consumption.

(2) Furthermore, generation of low-charge developer can be significantly reduced, background fogging can be prevented, and printing quality can be improved.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a principle diagram of the present invention, Fig. 2 is a configuration diagram of a first embodiment of the present invention, Fig. 3 is a work function relationship diagram of the first embodiment of the present invention, Figure 4 shows the first aspect of the present invention.
FIG. 5 is a configuration diagram of the second embodiment of the present invention, FIG. 6 is a work function relationship diagram of the second embodiment of the present invention, and FIG. 7 is an explanatory diagram of the prior art. , FIG. 8 is a conventional toner charge distribution characteristic diagram. In the figure, 1--image carrier (photosensitive drum), 4--toner, 7--developer carrier (developing roller), 8--layer thickness regulating member (blade), 10--carrier. Layer return f111 member 8 ((A) CB) Behind-the-scenes play-Tuno Okoke 10 layer S aphrodisiac member 8 Madarai vice 4wct
wb W quasi vI number tree complete ψ principle diagram Figure 1 (A) 0 0 5 0 S, S 0 (eV) (8) Pr3T'JI*I\I Mr. Iho [Three figures 3 and 67, Toner (Sra no Kiteria (6, o)) Figure 6

Claims (4)

[Claims] (1) A developer (4), and a developer conveying member (7,
10), and a developer regulating means (8) for regulating the layer thickness of the developer (4), the developer (4) is transferred to an electrostatic latent image by the developer conveying member (7, 10). In a developing device that conveys and develops an image carrier (1) on which a developer is formed, the developer conveying member (7, 10) and the developer regulating means (
8) and the work functions of the developer (4) are Wd and W, respectively.
b, Wt, (Wd-Wt)×(Wb-Wt)>
The developer conveying members (7, 10
), the developer regulating means (8), and the developer (4). (2) The developer (4) is a one-component developer, and the developer (4) is transported by the developer transport member (7, 10) in contact with the image carrier (1). The developing device according to claim 1, characterized in that it is a carrier (7). (3) The developer conveying members (7, 10) are connected to the carrier (1).
0) The developing device according to claim (1). (4) Claim (4) characterized in that a voltage is applied to the developer regulating means (8) to forcibly charge the developer (4).
1) The developing device described.