JPH0486876A - Development device - Google Patents

Abstract

PURPOSE:To provide a superior image which is free from an image irregularity at the time of development by providing a doctor blade with an electret layer. CONSTITUTION:A developer 14 forms a magnetic brush 18 on a developing sleeve 16 and the brush is restrained by the doctor blade 20 and reacts on an electrostatic latent image in a photosensitive layer 24 at a nip position to form a visible image of the developer, which is transferred by a transfer mechanism 34 to transfer paper. An electret dielectric layer is formed on the external surface layer of the doctor blade 20 so that the charge density of the electret layer is 5X10-<10> - 2X10-<7> C.cm<2>. When magnetic developer particles 18 are charged electrostatically and negatively, the external surface of the electret layer is charged electrostatically and negatively. The developer after being agitated is held on the sleeve surface and when the developer passes between the blade and sleeve, i.e. a nap cutting gap, the blade limits the amount physically; and the developer receives electric resiliency from the electret having the same polarity with an electrostatic charging electrode and is applied with the magnetic attractive force of the sleeve in some case to cohere by compression, so the concentration of the developer is made uniform and the electrostatic charging performance is uniformed.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an electrophotographic developing device.

More specifically, the present invention relates to a developing device capable of forming a developer magnetic brush formed on the surface of a developer conveying member (developing sleeve) in an even and appropriately thin layer and uniformly charging the brush.

(Prior Art) Magnetic brush development is widely used in electrophotographic methods, for example, a two-component developer consisting of a mixture of a magnetic carrier and electrostatic toner, or a one-component developer that itself has magnetic powder. electrifying a system magnetic developer to form a magnetic brush of the developer on a developer conveying member having a magnet inside;
The image is formed by moving this magnetic brush to the surface of the photoreceptor having an electrostatic image, and rubbing the surface with the magnetic brush under a bias electric field.

In addition, a developer amount regulating member (doctor blade) is provided adjacent to the sleeve surface, and the doctor blade scrapes off the tip of the flowing developer, which has become a magnetic brush, to supply the amount of developer to the photoreceptor surface. is regulated. The purpose of the doctor blade is to form a magnetic brush in a thin and uniform layer to prevent fogging or density unevenness caused by supplying too much developer.

(Problems to be Solved by the Invention) In the conventional developing method, an aluminum blade is used as a doctor blade, and the cutting gap (distance between the sleeve and the blade) is about 100 μm. However, conventional doctor blades have the following in.

The problem with HSL is that conventional doctor blades only physically restrict the developer, and there is no margin for precision (tolerance) in the cutting gap, so in order to control with high precision, it is necessary to install the blade. We have no choice but to be strict. Therefore, if the station of the blade does not work properly, image density unevenness, fogging, etc. are likely to occur.

Second! l! One 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 conditions, and the blade ends up merely physically processing it, so the developer is not deposited on the sleeve. A uniform developer layer or magnetic brush may not be formed. In such a case, the image quality becomes non-uniform during development.

The third problem is that the developer sent to the blade may have an uneven charge state, and since the developer is not subjected to any atmospheric processing by the blade, the unused material that is carried to the photoreceptor is It contains a large proportion of charged developer. Therefore, the image becomes non-uniform during development. The fourth issue is that the agitated developer may contain developer of opposite polarity (same polarity as the photoreceptor), and such developer may pass through the conventional blade and reach the photoreceptor. When sent,
This causes deterioration of image quality and disturbance during development.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrophotographic developing device in which the developer layer can be easily leveled and thinned using the cutting gap.

The object of the invention is also to. To provide an electrophotographic developing device capable of forming an excellent image during development by making the density of a developer layer on a sleeve uniform and reducing the proportion of uncharged developer supplied to a photoreceptor. be.

(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 developer on a surface, and a It consists of a developer conveying member that applies the developer to the electrostatic image area of the support, and a developer amount regulating member that is located close to the conveying member and regulates the amount of developer supplied, and the regulating member is an electret. layer, and the charge density (absolute value) of the electret dielectric layer is 5×10
A developing device is provided that satisfies the range of -10 to 2 x 10-'C/cm2.

The present invention may also be characterized in that the electret dielectric layer is a fluororesin.

(for production) In the present invention, a developer conveying member (hereinafter referred to as a sleeve) is used.

), 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,
After the developer layer is thinned to have a uniform density and a uniform charge amount, it is sent to a static image support (hereinafter referred to as 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.

An electret is a conductor that exhibits permanent electric polarization, and in the present invention, a layer of this electret 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 homopolar. 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. In addition, the charge density of the electret dielectric layer was set to 5X10""
The above effect is made even more effective by setting it in the range of 0 to 2X 1O-7C/cm2.

First, when the electret layer has the same polarity as the developer, the following effect is achieved.

The agitated developer is charged and held on the sleeve surface while being attracted by a magnet or the like of the sleeve, and passes through the gap between the blade and the sleeve, that is, 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, the doctor blade is 20, and the electret layer is 40. The magnetic developer particles 18 are, for example, negatively charged and are conveyed to the photoreceptor 22 by forming a magnetic brush with the sleeve 16 .

Electret N40 has 18 developer particles on its outer surface.
The charges are of the same polarity. Further, the charge density of the electret layer 40 is set to 5. IX 10-to-2
．． The range is 1×10′C/am2.

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 into a dense layer and thinner 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.

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. This effect is more effective when the developer and the electret layer have the same polarity.

Furthermore, in the present invention, as described above, the charge density of the electret layer (glycoside value) is 5X10-to 2X
It is desirable that the charge density of the electret layer be in the range of 10-'C/cm2, particularly in the range of I x 10-' to 1.5X, 10-"C/cm2. A thin layer of developer with uniform density is well formed, and toner scattering is prevented.

Next, when the developer and the electret layer have different polarities, the amount of developer is physically limited by the blade as it passes through, and the electret layer has an electrical attraction force that is opposite 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 through in a fully extended state, which gives more margin to the accuracy of the ear cutting gap.
To make the density of the developer uniform and the chargeability of the developer uniform.

In FIG. 3 for explaining this principle, the sleeve is 16, the photoreceptor is 22, the agitated 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 conveyed to the photoreceptor 22 by forming a magnetic brush with the sleeve 16 .

Electret #42 has developer particles 18 on its outer surface.
The charge is of opposite polarity. Further, the charge density of the electret layer 40 is set to 5. IX 10-'O to 2
．． It is in the range of IX 10-'C/cm2.

The developer 18 is regulated to some extent by the blade 20,
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 remains almost constant, unaffected by unevenness in shallowness. The fact that the density is uniform and that the density value takes a constant value indicates the above-mentioned effect during development.

Also, the developer passing through the doctor blade.

It is electrostatically affected by the electret layer,
Similarly, the non-uniform charging state that occurs in the agitated 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.

In this case, as mentioned above, the charge density of the electret layer is set to 5X 10-10 to 2X lo-7C/cm2.
range, especially lXl0-' to 1.5X10-''C/
It is desirable to set it in the range of cm2. When the charge density of the electric left layer is within the above range, a thin layer of developer with uniform charge density is well formed, and toner scattering etc. are prevented.

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 Similarly, the proportion of polar developer tends to be reduced.

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

FIG. 1 is an explanatory diagram of the principle of the developing device used in the present invention, 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 6 is supplied from above. The developer 6 is supplied into the lower developing device 1o through the feeder-equipped supply port 8, and development! Stirring within 10 #
The developer is stirred (in the case of a two-component developer, together with a carrier) and charged by a container 12.12.

Inside the developing device 1o, there is a developing sleeve 16 equipped with a large number of magnetic poles.
The developing sleeve 16 is supplied with the developer 14 after being triboelectrically charged, and a magnetic brush is formed by the developer on the sleeve surface. The length of the magnetic brush is adjusted by the doctor blade 2o, and the magnetic brush is conveyed to the nip position of the photosensitive layer 24 of the electrophotographic photosensitive drum 22.

The distance between the photosensitive drum 22 and the developing sleeve 16 is DD−.
The developing sleeve 16 and the photosensitive drum 22 are rotatably supported by a machine frame (not shown) so that the moving directions (arrows) at the nip position are the same (or opposite). Around the photosensitive drum 22, a corona charger 26 connected to a variable high voltage power source 25 and an exposure optical system 28 are arranged on the upstream side of the developing device 10 to generate an electrostatic charge with a predetermined surface potential. A latent image can be formed. Further, a bias voltage IW 33 equipped with a voltage adjustment mechanism 30 is connected between the photoconductor drum 22 and the developing sleeve 16, and a bias voltage IW 33 having the same polarity as the surface potential on the photoconductor/W 24 but lower than the surface potential is connected. A value (bias potential) can be applied. Furthermore, a transfer mechanism 34 is provided around the photosensitive layer 24 and downstream of the developing section for transferring the developer image onto copy paper.

In such a configuration, the developer 14 is transferred to the developing sleeve 1.
6 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 diagram of the main parts of the developing device according to the present invention. As shown in FIG. 2, an electret dielectric layer 40 is formed on the outer surface layer of the doctor blade 20, and the charge density of the electret layer is 5X 10-" to 2X 10-".
'C/cm2 range, especially I x 10-' to 1.5
It is formed in the range of X 1O-7C/cm2.

When the magnetic developer particles 18 are, for example, negatively charged, the outer surface of the electret layer 40 is negatively charged so that it has the same polarity as the developer particles 9.

As the material for the electret, any organic or inorganic material can be used as long as it is a film-forming material that can be permanently electrically polarized. Various polymeric materials are suitable. Suitable examples thereof include, but are not limited to, olefin resins such as polyethylene, polypropylene, ethylene-butene copolymers, ionically crosslinked olefin copolymers, and ethylene-acrylic copolymers; polyvinyl fluoride;
Polyvinylidene fluoride, vinyl fluoride/vinylidene fluoride copolymer, tetrafluoroethylene resin (PTFE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin i (PFA*1ii), tetrafluoroethylene-hexafluoride Fluororesins such as propylene copolymer resin (FEP resin); Chlorine resins such as polyvinyl chloride and chlorinated polyolefin; Thermoplastic polyesters such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; Nylon 6, Nylon 12, Nylon 6. 6
, polyamide such as nylon 6.10; various acrylic resins, etc. may be used alone or in combination of two or more.

Choleranouchi Temo, PTFE Tree II, PFllllfi, F
Fluororesins such as EP 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 thermal electretization method, electroelectretization method, radiation electretization method, 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 doctor blade, a layer of a non-electret polymer film may be provided on the blade surface, and then this polymer film layer may be converted to an electret layer by the above-mentioned method.
Alternatively, the electret film may be bonded to the blade surface via an adhesive layer. The former method is generally advantageous.

Further, the thickness of the electret layer is formed in a range of 0.005 to 2 mm, particularly 0.01 to 0.1 mm. The surface roughness of electret N42 is 0.02 to 2p
m, particularly in the range of 0.025 to 1 μm.

The gap D between the developing sleeve and the doctor blade, that is, the cutting gap D is 0.05 to 2.0 wm, particularly 0, 1 to 1.0 wm. It is desirable to set it to satisfy the range of 5wm. With such a set width, the developer layer D' formed on the sleeve is formed thinner than D, and the uniform layer thickness of the developer layer D' can be adjusted to a minimum of 0.05 mm. . The developer ND' 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.
．． 5wm, in the case of a -component developer, 0.05 to 0
．． It is desirable that the distance be within a range of 5 mm.

In the present invention, the magnetic pole in the developing sleeve (developer conveying member) preferably has a relatively low magnetic flux density within a range that does not cause carrier attraction, and is generally 400 to 1200 Gauss, particularly preferably 500 to 1000 Gauss. . The rotational speed of the developing sleeve is preferably within a relatively large range that does not cause developer scattering, and generally the peripheral speed is 5.
from 100 cm/see, especially from 10 to 80 a
It is preferable that it be within the range of m/see. Further, the distance It D D-3 between the developing sleeve and the photosensitive layer is 0. 5 to 3.5■, 0.0 in the case of a -component developer. 1 to 1. A range of 0 wm is appropriate.

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

As the two-component magnetic developer, a mixture of a magnetic carrier and an 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 yttrium oxide (Y3FesO
+ 2), iron cadmium oxide (CdFe20.),
@Gadolinium oxide (Gd, Fe6012), iron oxide (CuFe20a), iron oxide complex (PbFe+20+
e) - Nickel iron oxide (NiFe204), neodymium iron oxide (NdFeOs), barium iron oxide (BaF
e, 2 sheets, ), magnesium iron oxide (MzFe20.)
, iron manganese oxide (MnFe20a), lanthanum iron oxide (LaFeOs), etc. Sintered ferrite particles are used, and in particular, sintered ferrite particles have a composition consisting of one or more of iron oxide (LaFeOs), etc.
, Zn, N(, Mn, and Ni), soft ferrite containing at least one metal component, preferably two or more metal components selected from the group consisting of Coated particles are used, the particle size is 30 to 120 μm, especially 40 to 100 pvr, and the saturation magnetization is 40 to 7 Q emu/
g, especially those in the range 45 to 65 emu/g are advantageously used. Its volume resistivity is 10' to 1
It is better to be within the range of ゜2Ω country.

The toner used in the present invention is one in which a coloring agent and a charge control agent, or further toner compounding agents known per se, are blended into a fixing medium. The toner used in the present invention is lXl
0" to 3XIO'Ω' cm, especially 2X10" to 8
It is preferable to have a volume resistivity of XIO'' Ω·cm, and its dielectric constant is preferably in the range of 2°5 to 4.5, particularly 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: A substituent such as an atom, where n is 2 including zero.
It is an integer below. Examples of monomers represented by the following formulas include styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene, vinylxylene, and vinylnaphthalene.

Among these, styrene is preferred.

On the other hand, as an acrylic monomer, -0-R4 (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, acrylic acid, methacrylic acid, etc. In addition to the above-mentioned acrylic monomers, other ethylenically unsaturated carboxylic acids or their anhydrides,
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, especially 60:40 to 85:15
It is recommended that the range be within the range of . Also, use it! I! It is generally preferred that the fat has an acid value of 0 to 25. In addition, from the viewpoint of fixing properties, the glass transition temperature (Tz) of 50 to 65°C
It is good to have

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 black such as furnace black 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; virazolone red bond; 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 black (CI26150), and Subiron black, or 1:1 type or 2:1 type. metal salt dye,
Naphthenic acid metal salts, fatty acids, 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 a melt mixing/pulverization method, or spherical particles produced by a dispersion or suspension polymerization method.

The mixing ratio of the 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 5:95.
It is desirable that it be within the range of . In addition, the electrical resistance of the developer as a whole is 5 x 109 to 5 x 101'Ω'.
cra, particularly in the range of 1 x 10 to 4 x 101' ohm-cm, is preferred for the purposes of the present invention.

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

The electrostatic toner composition containing magnetic powder in an amount of 30 to 70% by weight, particularly 40 to 60% by IC amount, is used. The magnetic powder has a particle size of 0. 1
Triiron tetroxide (magnetite) jaferite in the range from 3 μm to 3 μm, especially those having the chemical compositions mentioned 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 it is separated from the electret 1W40. receives a repulsive force. The electret 140 is given a surface potential ES. The ears of the developer 18 are compressed as much as possible between the sleeve 16 and the electret 40, as shown in FIG. This is due to the electrical repulsive force of the electret 40 and the magnetic attractive force of the sleeve 16 described above. Therefore, electret 40
The developer magnetic brush located between the sleeve 16 and the sleeve 16 is compressed and becomes dense 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. Furthermore, since the spikes of developer are always in a concentrated state, the concentration or density of the developer passing through the sleeve 20 and the electret 40 takes a predetermined fixed value. This is because the concentration or density does not vary as in the conventional case, so the width of the ear cutting gap can be adjusted sensitively, 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 the surface roughness of the electret layer is formed to be within a certain range, the developer layer is subjected to moderate frictional resistance, and the fluidity is too good, resulting in insufficient compression and the electret layer. The developer layer does not become clogged or stuck between the sleeves, and the developer layer is not disturbed.

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 FIG. 3, a plurality of electret dielectric layers 42 are formed on the outer surface layer of the doctor blade 20, and the charge density of the electret layers is 5X 10-" to 2.
It is formed in the range of X 1O-7C/cm2, especially in the range of /x10i to 1HA-5/cm2.

For example, when the developer particles 18 are negatively charged, the outer surface of the electret layer 42 is positively charged so as to have a charge of opposite polarity to that of the developer particles 9.

The outermost surface of electret NI42 has a thickness of 0.005 to 2 mm, preferably 0.01 to 0.1 mm, and the surface roughness of electret #42 is 0.02 mm.
It is formed in the range of 2 μm to 2 μm, particularly 0.025 to 1 μm.

Further, the surface potential ES of the electret layer is preferably in the range of 200 to 1000V, particularly 300 to 900V. Such a surface potential provides sufficient attraction to the developer.

The surface potential ES of the electret layer 42 is 200 to 1o
OO■, Special i: Desirably in the range of 300 to 900V (7). 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. 2, and the same developing sleeve and photoreceptor are also used.

The same leaves and photoreceptors are also used.

It is desirable that the gap D2 between the developing sleeve and the doctor blade be set to be in the range of 0.05 to 2.0 mm, particularly 0.1 to 1.5 mm. With such a set width, the developer layer D2' formed on the sleeve is formed smaller than D2, and the uniform N thickness of the developer layer D2' can be adjusted to a minimum of 0.05 mm. Become. Magnetic brush developer #D 2'
depends on the type of developer, but in the case of a two-component developer,
0.5 to 1.5m, 0.0 for -component developer
It is desirable that it be within the range of 5 to 0.5+++m.

According to the present invention configured as described above, the -component-based charged developer 18 is regulated to some extent by the blade 16, and the developer 18A passing through it has spikes as shown in FIG. The sleeve 16 and the electret 42 are stretched as much as possible.

This is due to the electrical attraction force of the electret 42 and the magnetic attraction force of the sleeve 16 described above.

Therefore, the density or concentration between the electret 42 and the sleeve 16 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.

Also, because the spikes of developer are always in an extended state,
The concentration or density of the developer passing through the sleeve 16 and the electret 42 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.

Furthermore, in this case, since the surface roughness of the electret is formed within the above range, the developer flows smoothly without sticking to the surface of the electret layer. Therefore, no disturbance occurs in the developer layer.

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

Experimental Example 1 The electret layer of the blade was made of FEP resin, with a thickness of 0.3511 m, a surface roughness of 0.35 μm, a charge density of -4.5X 10-'c/cm, and a surface potential of was -600V, the surface tension was 19 dyne/an, and the polarity was the same as that of the developer.

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 am/sec, peripheral speed of the developing sleeve is 27 am/sec, photosensitive layer/sleeve rotation method is forward direction, magnetic pole inside the sleeve is 800 Gauss, distance between photosensitive layer and sleeve. 1 is 0. 2mm, compensation gap 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 0.003.

(2) Developer/91) (Length of panicle) was 0.2 mm.

(3) Image density unevenness was 0.09 or less.

Experimental Example 2 The electret layer of the blade was made of FEP resin, had a thickness of 0.275 mm, a surface roughness of 0.275 μm, and a charge density of 3. 7 X I O-”c/crrf,
The surface potential was 500V, the surface tension was 17 dyne/cn, and the polarity was opposite to that of the developer.

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 cm/sec, magnetic pole inside the sleeve is 800 gauss, distance between photosensitive layer sleeves giDo-s is 0.15 mm, compensation gap is 0.25+n+n, and one-component magnetic developer is used. A developer was used.

(1) The image density of the obtained copy was 1.32.

The fog density was 0.003.

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

(3) Image density unevenness was 0.1 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 exposed to electric attraction and magnetic attraction. Due to the action of force, the density becomes uniform and takes on a predetermined value. Therefore, the developer supplied to the support forms a thin layer with uniform density, and an excellent image without image unevenness can be provided during development. In addition, in this case, there is more margin in the accuracy of the ear cutting gap, making it easier to train the blade.
There is no possibility of fogging caused by excessive supply of developer.

Further, 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 to form an excellent image. Since the charge density of the electret layer is formed within a specific range and the charge density of the developer layer is not disturbed, a thin and uniform developer layer is formed during development, resulting in a good image.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the principle of an electrophotographic developing device according to the present invention, and FIG. 2 is a sectional view of a main part of FIG. 1. Third
The figure is a sectional view of essential parts showing another embodiment of the developing device according to the present invention. 2...Developing device, 16...Developing sleeve,
20... Doctor blade, 22... Photoreceptor,
40.42...Electret dielectric layer.

Claims (2)

[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 developer on its surface and transfers the developer to the electrostatic image area of the support. a developer conveying member for applying the developer; and a developer amount regulating member that is located close to the conveying member and regulates the amount of developer supplied, the regulating member having an electret layer, and the developer amount regulating member having an electret layer. Charge density is 5×10^-^1^0 to 2×10^-^7C/cm^
A developing device characterized by satisfying the following range. (2) The developing device according to claim 1, wherein the electret dielectric layer is a fluororesin.