JPH0432874A - Developing device - Google Patents

Abstract

PURPOSE:To maintain the holding safety of the charge of the electret layer of a blade for a long period and to continue the excellent state of an image by forming an electret with plural layers. CONSTITUTION:The electret 40 is a dielectric indicating a permanent electric polarizing action, provided on the blade 20 of the upper part of a sleeve 16 so that the layer of the electret has the same polarity as the electrifying polarity of a developer grain, and is formed with plural layers to continue the action much more. A developer is physically restricted by the blade 20 in its quantity, and besides, receives electric resiliency by the electret having the same polarity as the electrifying polarity of the developer, so that a developing layer is compressed and flocculated by the electric resiliency of the blade 20. Then, this compressive flocculation gives room to the precision of a gap for cutting nap, the density of the developer is uniformized, and the electrifiability of the developer is uniformized, as well. Thus, the holding safety of the charge of the electret 40 is improved, and the action of the blade 20 can be maintained for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrophotographic developing device. The present invention relates to a developing device that can form excellent images for a long period of time with little lag.

(Prior Art) In electrophotographic methods, magnetic brush development is widely used. A one-component developer is charged to form a developer layer on the developer amount regulating member (sleeve), the magnetic brush is moved to the surface of the photoreceptor having an electrostatic image, and the surface is exposed to a bias electric field. Image formation is performed by rubbing a developer layer under the surface.

In addition, there is a developer amount control I in close proximity to the sleeve surface. A member (doctor blade) is provided, and the doctor blade scrapes off the flowing developer layer, for example, the tips of magnetic brushes, thereby regulating the amount of developer supplied to the photoreceptor surface. The purpose of the doctor blade is to form a magnetic brush in a thin and uniform layer, so that too much developer is supplied to prevent capillary formation or density unevenness.

(Problems to be Solved by the Invention) In a conventional one-component developing device, an aluminum blade is used as a doctor blade, and the W cutting gap (distance between the sleeve and the blade) is about 100 μm.

However, conventional doctor blades have the following problems.

The first problem is that conventional doctor blades only physically restrict the developer, and there is no margin for precision (tolerance) in the cutting gap. We have no choice but to be strict. For this reason,
If the blade is not properly adjusted, uneven image density and capri are likely to occur.

The second problem is that the developer is sent to the blade after being stirred, but the developer is sent to the blade with uneven density or concentration depending on the stirring state, and the blade ends up merely physically processing the developer.

A uniform developer layer or magnetic brush may not be formed on the sleeve. In such a case, the image quality becomes non-uniform during development.

Problem II3 is that the developer sent to the blade may have an uneven charge state.

Since the developer is not electrically processed by the blade, it contains a large proportion of uncharged developer that is carried to the photoreceptor. Therefore, the image becomes non-uniform during development.

As for the j14 HM, there may be a developer of opposite polarity (same polarity as the photoreceptor) in the stirring # developer, and such a developer passes through the conventional blade and hits the photoreceptor. If it is sent, it causes a decrease in image quality and disturbances during development.

Furthermore, as will be described later, the present invention uses electret in the doctor blade, and although electret is said to be a dielectric material that exhibits permanent electric polarization characteristics, when actually used in a developing device, It has been observed that during use, the developer transportability and the selective support of specific polar particles are significantly reduced. This is because the electrical polarizability of commercially available polymer electrets tends to have poor charge retention stability at high temperatures and high temperature conditions, and the surface charge tends to decay over time due to relaxation and leakage. This seems to be due to the fact that in a developing device that is constantly in contact with charged developer, temporary exchange of electric charge between the electret and developer particles cannot be ignored.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electrophotographic developing device that allows a margin in the cutting gap accuracy and allows easy adjustment of the cutting gap.

The object of the invention is also to. By making the density of the developer layer on the sleeve uniform, reducing the proportion of uncharged developer supplied to the photoconductor, and reducing the amount of developer supplied to the photoconductor with opposite polarity, it is possible to improve the development performance. An object of the present invention is to provide an electrophotographic developing device that can form images with high quality.

A further object of the present invention is to provide an electrophotographic developing device that can maintain the blade's function for a long time by improving the stability of holding the charge of the electret.

(Means for Solving the Problems) According to the present invention, a support for supporting an electrostatic image, a mechanism for charging a powder developer, a mechanism for holding and conveying the charged powder developer on a surface, and a The VJ member consists of a developer amount regulating member that applies the developer to the electrostatic image area of the support, and a developer amount regulating member that is close to the conveying member and regulates the supply amount of the developer. Provided is a developing device characterized by having a plurality of electret layers.

The present invention may be characterized in that the electret layer is made of a fluororesin.

The present invention also includes: l! As the image silver agent, a two-component developer consisting of a magnetic carrier and a electrostatic toner can be used, or a one-component toner containing magnetic powder or non-magnetic can be used.

(Function) In the present invention, the developer amount regulating member C will hereinafter be referred to as a sleeve. ), a developer layer or this magnetic brush is formed on the sleeve, and a developer amount regulating member (hereinafter referred to as a doctor blade) provided close to the sleeve is used to thin the developer layer. After making the density uniform and the amount of charge uniform, the electrostatic latent image support (hereinafter referred to as
(called a photoreceptor). Also, in the case of magnetic developers, a magnet within the sleeve is necessary to transport the developer in the form of a magnetic brush and into contact with the photoreceptor.

Electret is a dielectric material that exhibits permanent electrical polarization, and in the present invention, the electret layer is provided on the blade above the sleeve so that it has the same polarity or the opposite polarity to the charged polarity of the developer particles. Preferably they are of the same polarity. In addition, when the polarity is the same as that of the developer particles, and when the polarity is opposite to the developer particles, the effect is substantially the same, although the action is different. Moreover, by forming the electret layer as a plurality of layers, the above-mentioned effect can be further sustained.

First, when the charge on the electret layer is the same polarity as the developer, the developer after stirring is charged and held on the sleeve surface while being attracted by the magnet etc. of the sleeve, which is effective due to the following action. , passing between the blade and the sleeve, i.e. through the ear cutting gap. When the developer passes through the blade, the amount of the developer is physically limited by the blade and is also subjected to an electrical repulsive force by the electret having the same polarity as the developer charging electrode. Therefore, the developing layer is compressed and agglomerated by the electric repulsion of the blade and, in some cases, the magnetic attraction of the sleeve.

This compressed aggregation gives a margin to the precision of the cutting gap, makes the density of the developer uniform, and makes the charging property of the developer uniform.

In FIG. 2 for explaining this principle, the sleeve is 16, the photoreceptor is 22, the agitated developer is 18, and the doctor blade is 20. and the electret layer is 40.41. The magnetic developer particles 18 are negatively charged, for example, and are conveyed to the photoreceptor 22 by forming a magnetic brush with the sleeve 16 . The outer surface of the electret layer 40 is charged with the same polarity as the developer particles 18 . In addition, the inner electret layer 41 may have the same polarity as the electret layer 40 or a different polarity, but in particular, it is preferable to stack the electret layers 40 and 41 so that their respective bonding surfaces have the same polarity to reduce the charge of the electret layer. desirable for stability.

The developer 18 is regulated to some extent by the blade 20,
The spiked developer that is passing through is compressed between the sleeve 16 and the electret 40. This is due to the electrical repulsive force of the electret 40 and the magnetic attractive force of the sleeve 16. Therefore, the developer can be compressed and formed in a dense state and at a width yII# greater than the width of the cutting gap. This is an electrical regulation in addition to the conventional regulation based on physical action.

It is understood that this means that the ear cutting gap may be wider than in the past, and that the requirements for gap accuracy are less strict. Further, the developer magnetic brush located between the electret 40 and the sleeve 16 is dense and has no gaps, and its density or concentration is uniform, and the value of the density itself is not affected by density unevenness of the developer during agitation. It is not affected by density unevenness and remains almost constant. The fact that the density is uniform is that
Although the effect is as described above, it is understood that the fact that the value of the density itself during stirring is not affected reduces the accuracy error between the ear cutting gaps and provides a margin for tolerance.

Also, the developer passing through the doctor blade.

It is electrostatically affected by the electret layer,
The non-uniform charging state that occurs in the stirring developer is made uniform by the electric action of the electret, and the proportion of uncharged developer and opposite polarity developer tends to be reduced. This action is 5
It is more effective when the developer and the electret layer have the same polarity.

Furthermore, in the present invention, it is important to have multiple electret layers as described above. The stacked electret layers may have the same polarity or different polarities, but it is particularly preferable that the electret layers have the same polarity, as this increases the charge retention stability of the surface electret layer.

It is unclear how having multiple layers of electret contributes to the charge on the electret surface layer, but
This effect can be seen whether the polarity is the same or different, so even if the charge is transferred to the surface during development, the polarized charge of the electret in the inner layer promotes the recovery of the charge in the outer layer. It is clear that Furthermore, by forming the electret layer in multiple layers and making the electret layer thinner, the charge density can be increased, so it is understood that the action of the blade can be further enhanced. In this way, since the charge of the electret layer is maintained for a long time, the above-mentioned effect is maintained for a long time and the practicality is increased.

Next, when the developer and the electret layer have different polarities, the developer is not only physically reduced in amount by the blade when passing through it, but also receives an electrical attraction force due to the electret with the opposite polarity to the charged electrode of the developer. receive. Furthermore, even when passing through the sleeve, it is constantly receiving magnetic attraction from the sleeve. Therefore, the magnetic brush on the sleeve passes in a fully extended state, which gives a margin to the precision of the cutting gap, makes the density of the developer uniform, and makes the charging property of the developer uniform.

In Figures 1 and 3 to explain this principle, the sleeve is 16. The photoreceptor is 22. The stirring developer is 18, the doctor blade is 20, and the electret layer is 42. The magnetic developer particles 18 are, for example, negatively charged, and are distributed to the photoreceptor 22 by forming a magnetic brush with the sleeve 16 . The electret layer 42 has an outer surface covered with developer particles 1.
The charge is opposite to that of 8. Further, the inner electret layer 41 may have the same polarity as the electret layer 42 or a different polarity, but it is particularly preferable that the electret layers 42 and 41 are stacked so that their bonding surfaces have the same polarity.

The developer 18 is regulated to some extent by the blade 2o.
The spiked developer that is passing through is stretched between the sleeve 20 and the electret 42. This is due to the electrical attraction force of the electret 42 and the magnetic attraction force of the sleeve 16. Therefore, the developer layer under tension tends to be divided into parts based on the balance point of these suction forces, and the part near the blade remains untransported, while the part near the sleeve remains on the sleeve side. It becomes a substantial developing layer.

Therefore, the thickness of the developer can be formed into a thin layer about half the thickness of the ear cutting gap. It is understood that this means that the accuracy requirements for the ear cutting gap are more relaxed than in the past, and gap clogging becomes less likely to occur. Further, the ears of the developer magnetic brush located between the electret 42 and the sleeve 16 are in a fully extended state, and the density or concentration thereof is uniform, and the value of the density itself is also due to the density unevenness of the developer during stirring. It is not affected by density unevenness and remains almost constant. The fact that the density is uniform and that the density value takes a constant value is due to the effect described above.

In addition, the developer passing through the doctor blade is electrostatically affected by the electret layer, and the non-uniform charging state that occurs in the agitated developer is turned into a car by the electric action of the electret.

The proportion of uncharged developer and reverse polarity developer tends to be reduced. Furthermore, by using a plurality of electret layers, sufficient stability can be obtained as described above.

(Embodiments) Hereinafter, preferred embodiments of the developing device according to the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 shows the y! of the developing device used in the present invention. , which is a logical explanatory diagram, and the developing device of the present invention is not limited to such a structure.

As shown in FIG. 1, a normal developing device 2 is provided with a box-shaped developer supply mechanism 4, and a developer supply mechanism 4 is provided from above.
is supplied. The developer 6 is supplied to the lower developing device 10 through the supply port 8 with a feeder, and the development is completed! The developer is stirred by a stirrer 12, 12 (in the case of a two-component developer, the number is the same as the carrier) and charged.

Inside the developing device 10 is a developing sleeve 16 equipped with a large number of ms.
The developing sleeve 16 is supplied with the developer 14 after being triboelectrically charged, and a magnetic brush 18 is formed on the sleeve surface by the developer. The length of the magnetic brush is adjusted by a doctor blade 20, and the magnetic brush is conveyed to the nip position of the photosensitive layer 24 of the electrophotographic photosensitive drum 22. The photosensitive drum 22 is arranged at a distance D D-5 from the developing sleeve 16 .
The photosensitive drums 22 are rotatably supported by a machine frame (not shown) and are driven so that the moving directions (arrows) at the nip position are the same (or opposite).

A corona charger 26 connected to a variable high voltage power supply 25 and an exposure optical system 28 are arranged around the photoreceptor drum 22.
is disposed upstream of the developing device 10 to form an electrostatic latent image with a predetermined surface potential. A bias power supply 33 equipped with a voltage adjustment mechanism 30 is connected between the photosensitive drum 22 and the developing sleeve 12, and a bias power source 33 having a voltage adjustment mechanism 30 is connected to the photosensitive drum 22 and the developing sleeve 12. A value (bias potential) can be applied. Furthermore, a transfer mechanism 34 for transferring the developer image onto copy paper is arranged downstream of the developing section around the photosensitive layer 24.

In such a configuration, the developer 14 is transferred to the developing sleeve 1.
2 to form a magnetic brush 18 and a doctor blade 20
After being regulated by the developer, the developer reacts with the electrostatic latent image on the photosensitive layer 24 at the nip position to form a visible image of the developer on the photosensitive layer 24. The formed visible image is transferred to transfer paper by a transfer mechanism 34.

FIG. 2 is an explanatory view of the main parts of the developing device according to the present invention, in which the electret layer is at the same polarity as the developer. 12
As shown in the figure, a plurality of electret dielectric layers 40, 41 are formed on the outer surface layer of the doctor blade 20. For example, when the magnetic developer particles 18 are negatively charged, the outer surface of the electret layer 40 is negatively charged so that the outer surface thereof has the same polarity as the developer particles 9.

Further, the outer surface of the electret layer 40 has a low critical surface tension. The inner electret layer 41 may have the same polarity as the electret layer 40 or may have different polarity, but desirably, the bonding surfaces have the same polarity.

As the electret material, any film-forming material that can be permanently electrically polarized can be used, whether organic or inorganic.

Various polymeric materials are suitable in terms of ease of electret formation and ease of coating formation. Suitable examples thereof include, but are not limited to, polyethylene.

Olefin resins such as polypropylene, ethylene-butene copolymer, ionically crosslinked olefin copolymer, ethylene-acrylic copolymer; polyvinyl fluoride, polyvinylidene fluoride, vinyl fluoride/vinylidene fluoride copolymer, tetrafluoride Ethylene resin (PTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (PF
A resin), fluororesin such as tetrafluorinated ethylene-hexafluorinated propylene copolymer resin (FEP resin); chlorine resin such as polyvinyl chloride, chlorinated polyolefin; polyethylene terephthalate, polyethylene naphthalate.

Thermoplastic polyesters such as polybutylene terephthalate; polyamides such as nylon 6, nylon 1''L, nylon 6.6 and nylon 6.10; various acrylic resins, etc. are used singly or in combination of two or more types.

Among these, PTFE resin, PFA resin, FEP
Fluororesins such as resins are preferred because they have good critical surface tension, good charge retention, and good durability.

Electret production is performed by applying any method known per se, such as a thermal electretization method, an electroelectretization method, a radiation electretization method, a photoelectretization method, etc., depending on the type of polymer used. Thermal electretization method and electroelectretization method are advantageously applied to the above-mentioned polymers, especially fluororesins.

Further, in order to provide an electret layer on the surface of the developing blade, a layer of a polymer film that has not been made into an electret may be provided on the surface of the blade, and then this polymer film layer may be made into an electret by the above-mentioned method. The former method, in which the chemical film may be attached to the blade surface via an adhesive layer, is generally advantageous.

The outermost surface of the electret layer 4o has a thickness of O
, OO573~2 m, special f:o, o1~0. 1
is desirable, and the charge density σ is 5×1O-II! to 2
X 10-'c/crrf, particularly preferably in the range of IXIQ-9 to 1.5X10-7c/cbo. When the thickness is within the above range, workability is good. Further, the thickness greatly affects the charge density, and as the electret layer becomes thinner, the charge density improves. If the charge density is within the above range, the developer passing through the blade will form a thin layer with good precision and its density will be uniform. However, it can sufficiently influence the charge of the developer and make the charge of the developer uniform. In addition, the surface potential E of the electret layer
S is preferably in the range of 20073 to 1000V, particularly 300 to 900V. Such a surface potential provides sufficient attraction to the developer.

The thickness of the electret layer 41, which is the inner surface, is 0.0.
05 to 2 am, especially 0.01 to 0.1 μm, and the charge density σ is 5×1° to 2×10−
"c/cn (, especially lXl0-9 to 1, 5
It is desirable that it be in the range of 10-7c/cbo.

When the charge density is within the above range, it can be understood that even when the charge retention property of the outer surface layer 40 deteriorates, the polarized charge of the inner #41 is within a range that can be temporarily exchanged with the outer surface layer.

Further, the surface potential ES' where the electret layer 41 is in contact with the outer surface layer 40 is 2007th 1000V, special +: 30
It is desirable that the voltage be in the range of 0 to 900V. Such a surface potential provides sufficient electrical action to the outer surface layer.

The gap D between the developing sleeve and the doctor blade, that is, the cutting gap D is 0.05 to 2.0 m, particularly 0.1 to 1.0 m.
It is desirable to set the range to satisfy a range of 5 m. With such a set width, the developer layer D' formed on the sleeve is formed thinner than D, and the developer layer #D'
It is possible to uniformly adjust the lWK to a minimum of 0.0!5 mm. The developer layer D' of the magnetic brush depends on the type of developer, but in the case of a two-component developer, it is 0.5 to 1.5.
mm, in the case of a -component developer, 0.05 to 0. 5
It is desirable that it be within the ED range.

In the present invention, the i-feed in the developing sleeve (developer amount regulating member) preferably has a relatively small magnetic flux density within a range that does not cause carrier attraction, and is generally 400 to 1200 Gauss, particularly 500 to 1000 Gauss. Good. The rotational speed of the developing sleeve is preferably within a relatively large range that does not cause developer scattering, and the peripheral speed is generally 5 to 100 cm/see, particularly 10 to 80 cm/see.
It is preferable that it be within the range of m/see. Further, the distance D d D-5 between the developing sleeve and the photosensitive layer is 0°5 to 3.0° in the case of a two-component developer. 5 mm, and in the case of a -component type developer, a range of 0.1 to 1.0 mm is appropriate.

In the present invention, the photoreceptor includes various types of photoreceptors conventionally used in electrophotography, such as selenium photoreceptors, amorphous silicon photoreceptors, zinc oxide photoreceptors, cadmium selenide photoreceptors, cadmium sulfide photoreceptors, etc. All organic photoreceptors etc. are used.

As the two-component magnetic developer, a mixture of a magnetic carrier and electrostatic toner is used, and the magnetic carrier used here is a ferrite carrier or an iron powder carrier. Examples of ferrite carriers include iron zinc oxide (Z
nFe20a), iron indolium oxide (Y3FesO+
2), iron cadmium oxide (CdFe20.), iron gadolinium oxide (GdiFe50+2' copper iron oxide (C
uFe20a), iron oxide N (PbFe120+9)
, iron nickel oxide (NiFe20.), iron neodymium oxide (NdFeO3), iron oxide barium (BaFe12o)
19), iron magnesium oxide (M+:Fe20a), iron manganese oxide (WnFe20t), iron oxide lanthanum (L
Sintered ferrite particles having a composition consisting of one or more types such as aFeO3) are used, and in particular Cu, Zn
Soft ferrite, such as copper-zinc-magnesium ferrite, containing at least one, preferably two or more, metal components selected from the group consisting of , Ng, Mn and N1, or particles thereof coated with wood, etc. things are used.

Its particle size is 30 to 120 μm, f# is 40 to 10
At 0 μ+a, a saturation magnetization in the range of 40 to 70 emu/H, particularly 45 to 65 emu/H is advantageously used. Its volume resistivity is 106 to 1012
It is better to be in the range of Ω■.

The toner used in the present invention is one in which a colorant and a charge control agent, or a toner compounding agent known per se, is blended into a fixing resin medium.
O3 to 3X109Ω・crn-especially 2X108 to 8
It is preferable to have a volume resistivity of X1o8Ω·cm, and a dielectric constant of 2.5 to 4.5. In particular, it is desirable that it be in the range of 3.0 to 4.0.

The fixing resin medium, colorant, charge control agent, and other toner compounding agents for the toner are preferably selected and combined so as to obtain the above characteristics. First, as the fixing resin medium, a styrene resin, an acrylic resin, or a styrene-acrylic copolymer resin is generally used.

The styrene monomer used in these resins has the following formula (wherein R1 is a hydrogen atom, a lower alkyl group (having 4 or less carbon atoms), or a halogen atom, and R2 is a lower alkyl group or a halogen atom). (n is an integer of 2 or less including zero), such as styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene, vinylxylene, vinylnaphthalene, etc. can be mentioned. Among these, styrene is preferred.

On the other hand, as an acrylic monomer, the following formula (3)% formula% (wherein R3 is a hydrogen atom or a lower alkyl group,
R4 is a hydrogen atom or an alkyl group having up to 18 carbon atoms.

), such as ethyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, agrilic acid, methacrylic acid, etc. In addition to the above-mentioned acrylic monomers, other ethylenically unsaturated carboxylic acids or their anhydrides 1
For example, maleic anhydride, fumaric acid, maleic acid, crotonic acid, itaconic acid, etc. can also be used.

Styrene-acrylic copolymer resin is one of the suitable resin media, and the styrene monomer (A) and acrylic monomer (B) have a ratio of A:B=50:50 to 90. :10, particularly preferably in the range of 60:40 to 85:15. In addition, the resin used is generally ○ to 25
It is preferable to have an acid value of . Further, from the viewpoint of fixing properties, it is preferable to have a glass transition temperature (Tg) of 50 to 65°C.

As the coloring agent contained in the resin, the following inorganic or organic pigments, dyes, etc. may be used alone or in combination of two or more. Carbon blanks such as furnace blanks and channel black; Iron black such as triiron tetroxide; Titanium dioxide such as rutile type or anatase type; Phthalocyanine blue; Phthalocyanine green; Cadmium yellow; Molybdenum orange; Pyrazolone red; Fast violet B, etc.

As the charge control agent, any charge control agent known per se may be used, such as oil-soluble dyes such as Nigrosine Base (CI50415), Oil Blank (CI26150), Subiron Black, or 1:1 type or 2:1 type. Metal salt dyes, naphthenic acid metal salts, fatty acids and soaps, resin acid soaps, etc. are used.

The particle size of the toner particles is 8 to 14 μm on a volume basis, especially 10 μm as measured by a Coulter counter.
The particle size is preferably in the range of 12 μm to 12 μm, and the particle shape may be amorphous particles produced by the melt Wli kneading/pulverization method, or spherical particles produced by the dispersion or suspension polymerization method.

The mixing ratio of toner and magnetic carrier varies depending on the physical properties of the toner and magnetic carrier, but the weight ratio is generally 1:99 to 10:90, particularly 2:98 to 5:9.
95, and the electrical resistance of the developer as a whole is 5X10' to 5X101''Ω.
'cm, particularly in the range 1X10'' to 4X101@Ω·C-, is preferred for the purposes of the invention.

The one-component magnetic developer used in the present invention includes:

Although it is not necessary to contain magnetic powder, the electrostatic toner composition preferably contains 30 to 70% by weight, particularly 40 to 60% by weight of magnetic powder. i
As a type II powder, the particle size is 0. Triiron tetroxide (magnetite) or ferrite in the range of 1 to 3 μm, especially those having the chemical compositions described above, are used. Other components may be the same as the above-mentioned components in the two-component toner.

According to the present invention configured as described above, the -component or two-component charged developer 18 is regulated to some extent by the blade 20, and the developer 18 passing through is separated from the electret layer 40. receives a repulsive force. The electret layer 40 provides a surface potential ES. As shown in FIG.
0 and compressed as much as possible. This is due to the electrical repulsive force of the electret 40 and the magnetic attractive force of the sleeve 16 described above. Therefore, the developer magnetic brush located between the electret 40 and the sleeve 16 is compressed into a dense state with no gaps, and its density or concentration becomes uniform. Also, the developer is compressed and its volume becomes smaller, forming a thin layer that is about half the size of the gap. As mentioned above, this makes the requirement for gap accuracy less strict, and also prevents the developer from adhering to the blade surface, thereby preventing gap clogging. Further, since the spikes of the developer are always compressed and aggregated, the concentration or density of the developer passing through the sleeve 20 and the electret 40 takes a predetermined value. Since the concentration or density does not vary as in the conventional case, the width of the ear cutting gap can be adjusted in a sensitive manner, and there is a margin for the tolerance.

In addition, the developer passing through the doctor blade is electrostatically affected by the electret layer, and the non-uniform charging state that occurs in the agitated developer is made uniform by the electric action of the electret.

The proportion of uncharged developer and reverse polarity developer tends to be reduced.

Furthermore, in this case, since there are multiple electret layers,
Even if the outer surface electret layer suffers a decrease in polarization, the electret polarization of the inner layer prevents the extreme decrease in polarization of the outer surface layer and quickly recovers, so that the electret layer 40 maintains a stable charge. .

FIG. 3 is an explanatory view of the main parts of the developing device used in the present invention, in which the electret layer is at a different polarity from the developer. As shown in Figures 1 and 3, a plurality of electret dielectric layers 42 and 41 are formed on the outer surface layer of the doctor blade 20, and the outer surface of the electret layer 42 has a low critical surface tension. The magnetic developer particles 18 are
For example, when negatively charged, the outer surface of the electret layer 42 is positively charged so that it has an opposite magnetic charge to that of the developer particles 9. Moreover, the inner electret layer 41 may have the same polarity as the electret layer 42, or may have a different polarity, but preferably they have the same polarity.

The electret layer 40, which is the outermost surface, has a thickness of
0.005 to 2ma, special i: 0. 01 to 0.
1 cabinet is desirable, and the charge density σ is 5X10-II! 〜2XI0-7c/an(, especially lXl0-9
It is desirable that it be in the range of 1.5 x 10-7c/cnf.

In addition, the surface potential ES of the electret layer is 200 to 1000V, Special J: 300 to 900V.
It is desirable to be in the l range. Such a surface potential provides sufficient attraction to the developer.

The critical surface tension of the electret layer 40 is 31dyne
/ country, particularly preferably 25 dyne/mouth or less. If the critical surface tension of the electret layer is higher than the above range, the developer tends to stick to the blade surface, and the developer does not move smoothly on the surface of the electret layer, causing unevenness in the magnetic brush. There are times when the effects of this are not fully demonstrated.

The thickness of the electret layer 41, which is the inner surface, is 0.0.
05 to 2, particularly preferably 0.01 to 0.1, and the charge density σ is 5 x 10-1 to 2 x 10-
7c/c, especially lXl0-' to 1. 5 x 1
It is desirable that it be in the range of 0-7c/crd.

When the charge density is within the above range, it can be understood that even when the charge retention property of the outer surface layer 40 deteriorates, the polarized charges of the inner layer 41 are within a range that can be temporarily exchanged with the outer surface layer.

Further, the surface potential ES' where the electret layer 41 is in contact with the outer surface layer 40 is 200 to 1000 V, special G: 30
It is desirable to be in the 073 to 900 v no range g. Such a surface potential provides sufficient electrical action to the outer surface layer.

In the present invention, the material of the electret layer and the method of applying the same are the same as those used in the apparatus shown in FIG. 112, and the developing sleeve and photoreceptor are also the same.

The gap D2 between the developing sleeve and the doctor blade, that is, the cutting gap D2 is 0.05 to 2.01. In particular, it is desirable to set it to satisfy the range of 0.1 to 1.5++e. With such a set width, the developer layer D2' formed on the sleeve is formed thinner than D2,
Further, it is possible to control the uniform layer thickness of the developer layer D2' to a minimum of 0.05 rm. Developer layer D2' of magnetic brush
depends on the type of developer, but in the case of a two-component developer,
0. 5 to 1.5 mm, 0 for -component developer
．． It is irritating that it is within the range of 0.05 to 0.5 aa.

According to the present invention configured as described above, the -component-based charged developer 18 is regulated to some extent by the blade 20, and the developer 18 during one passage is regulated to some extent by the blade 20. ! As shown in FIG. 3, the ears stand up and are stretched as much as possible between the sleeve 20 and the electret layer 42.

This is due to the electrical attraction force of the electret 42 and the sleeve 1
This is due to the magnetic attraction force of 6. Therefore, the developer magnetic brush located between the electret 42 and the sleeve 16 is fully extended, and its density or concentration becomes uniform. Further, the developer separates at approximately the midpoint of the cutting gap, forming a thin layer that is about half the width of the gap. As mentioned above, this makes the requirement for gap accuracy less strict and prevents gap clogging. Further, since the developer spikes are always in an extended state, the concentration or density of the developer passing through the sleeve 20 and the electret 42 takes a predetermined fixed value. Since the concentration or density does not vary as in the conventional case, the width of the ear cutting gap can be adjusted in a sensitive manner, and there is a margin for the tolerance. In addition, the developer passing through the doctor blade is electrostatically affected by the electret layer, and the non-uniform charging state that occurs in the agitated developer is made uniform by the electric action of the electret, and the uncharged developer and reverse The proportion of polar developer tends to be reduced.

Furthermore, in this case, since there are multiple electret layers,
Even if the outer surface electret layer suffers a decrease in polarization, the electret polarization of the inner layer prevents the extreme decrease in polarization of the outer surface layer and quickly recovers, so that the electret layer 42 maintains a stable charge. .

The invention will be further illustrated by the following experimental examples.

Experiment fs1 The outer electret layer of the blade was made of FEP resin, with a thickness of 0.025I1m, a charge density of -3.7X10-8c/c, and a surface potential of -3.7X10-8c/c.
-500■, surface tension is 17 dyne/am.

and the same polarity as the developer charge.

In addition, the inner electret layer is formed of FEP resin,
Its thickness is 0. 025 mm, the charge density is 3.7 x 10-8 c/c, and the surface potential is 500V.

The electret layer bonding surfaces are of the same polarity.

Such a blade was attached to an improved electrophotographic copying machine DC-1120 manufactured by Sanda Kogyo Co., Ltd., which uses an amorphous selenium photoreceptor, and transfer and fixing were performed under the following conditions.

condition is.

The circumferential speed of the photoreceptor is 13. 5 as/sec, peripheral speed of the developing sleeve is 27 co/sec, photosensitive layer/sleeve rotation method is forward direction, magnetic pole inside the sleeve is 800 Gauss, photosensitive layer sleeve amount ratio! Dos is 0.2mm
.

Complementary gap is 0.3nn, Further, a one-component magnetic developer was used as the developer.

(1) The image density of the obtained copy was 1.37, and the fog density was 0.003.

(2) The developer layer (length of the panicle) was 0.2 m.

(3) Image density unevenness was 0.09 or less.

Experimental Example 2 The outer electret layer of the blade was made of FEP resin, and had a thickness of 0.0125 mL and a charge density of 8. The surface potential was 600 V, the surface tension was 19 dyne/an, and the polarity was different from that of the developer.

In addition, the inner electret layer is formed of FEP resin,
Its thickness is 0.0125111L, charge density is -8.9X10c/c, and surface potential is -
It is 60OV.

The electret layers are mutually homopolar.

Such a blade was attached to an improved electrophotographic copying machine DC-112C manufactured by Sanda Kogyo Co., Ltd., which uses an amorphous selenium photoreceptor, and transfer and fixing were performed under the following conditions.

The conditions are: The circumferential speed of the photoreceptor is 13. 5 cm/see, peripheral speed of the developing sleeve is 27 am/sea, photosensitive layer/sleeve rotation method is forward direction, magnetic pole inside the sleeve is 800 Gauss, distance between photosensitive layer and sleeve D D -S is 0.15 mm,
The compensation gap was 0.3 mm, and a one-component magnetic developer was used as the developer.

(1) The image density of the obtained copy was 1.34, and the fog density was 0002.

(2) The developer layer (length of the spike) was 0.15 nn.

(3) Image density unevenness was 0.08 or less.

(Effects of the Invention) As explained above, according to the present invention, since the electret layer is provided on the doctor blade, the charged developer layer is located between the blade and the sleeve, and is capable of attracting both electric and magnetic attraction. Due to the action of force, the density becomes uniform and takes on a predetermined value. For this reason.

The developer supplied to the support forms a thin layer with uniform density,
Excellent images with no image unevenness etc. can be provided during development.

Further, in this case, since there is a margin in the radius of the cutting gap and its accuracy, the blade can be easily adjusted, and there is no possibility of oversupplying the developer and causing fogging or the like.

Furthermore, since the electret acts electrically on the developer, the developer supplied to the support has good charging properties and is transferred well to the latent image portion of the support, forming an excellent image. Furthermore, since the electret is formed in multiple layers, the electret layer of the blade maintains charge retention stability for a long period of time. Therefore, the image is good during development and can remain in good condition for a long time.

[Brief explanation of drawings]

FIG. jI1 is a diagram for explaining the principle of an apparatus using the electrophotographic developing method according to the present invention, and FIG. 2Ugj is a sectional view of a main part of FIG. 1. FIG. 3 is a sectional view of a main part showing another embodiment of a developing device in which the electrophotographic developing method superior to the present invention is used. 2...Developing device, 16...Developing sleeve,
20... Doctor blade, 22... Photoreceptor,
40.41.42...Electret dielectric layer. Patent Ento Hatake Mita Kogyo Co., Ltd. Agent Patent Attorney Ikuo Meiki Diagram 2

Claims (4)

[Claims] (1) A support that supports an electrostatic image, a mechanism that charges a powder developer, and a mechanism that holds and transports the charged powder developer on the surface and transfers the developer to an electrostatic image area of the support. and a developer amount regulating member that is located close to the carrying member and regulates the amount of developer supplied, and the regulating member has a plurality of electret layers. developing device. (2) The developing device according to claim 1, wherein the electret layer is made of a fluororesin. (3) Claim 1 or 2, wherein the bonding surfaces of the plurality of electret layers are of the same polarity.
Developing device as described in section. (4) Claim 1 or 2, wherein the bonding surfaces of the plurality of electret layers have different polarities.
Developing device as described in section.