JPH0367286A - Developing method having excellent reproducibility of image - Google Patents

Abstract

PURPOSE:To prevent the missing at the front end and rear end of respective line having a specified line width and to form images having a high density and high quality by specifying the contact frequency of a carrier to be defined as the product of the number of carrier contacts per area of a photosensitive body and a developing length. CONSTITUTION:The rubbing of a magnetic brush and the photosensitive body is so set that the frequency (k) defined by equation I attains 100 to 700. In the equation I, n denotes the number of the carrier contacting per area of the photosensitive body determined from a scanning type electron microscope photograph for the corodion fixed magnetic brush and L denotes the developing length stipulated by equation II. In the equation II, Nip denotes the nip width (mm) of a developer on the surface of the photosensitive body; Vs denotes the moving speed (mm/sec) of the developing sleeve; Vd denotes the developing length stipulated by moving speed (mm/sec) of the surface of the photosensitive body. The specified line width of each of the respective lines is obtd, in this way while the image density is increased at the time of the reproduction of the multiple fine lines. The missing at the front end and rear end is thus prevented and the images having the high density and high quality are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing method with excellent image reproducibility. The present invention relates to a developing method that prevents so-called leading edge chipping and trailing edge chipping.

(Prior Art) Images characterized by setting a developing sleeve and toner are widely used in commercial electrophotographic copying machines, and when developing a charged image, a magnetic brush of this developer is installed inside. The magnetic brush is formed on a developing sleeve provided with magnetic poles, and this magnetic brush slides with the photoreceptor having a charge image to form a magnetic brush.

Many proposals have already been made regarding the setting of development conditions, etc. For example, in Japanese Patent Application Laid-Open No. 172660/1989, a two-component developer consisting of a ferrite carrier and a electrostatic toner is used, and the toner is It is described that an image with high density and excellent gradation can be obtained by setting the density, the photosensitive drum/developing sleeve peripheral speed ratio, and the main pole angle of the magnetic carrier within a certain range. Also, JP-A-61-11
Publication No. 8767 discloses that when developing using a two-component developer, by selecting the surface potential, D-3 (photoreceptor drum - developing sleeve) distance, and developing sleeve resistance value within a certain range, it is possible to eliminate image unevenness. It has been shown that high quality images can be obtained.

Recently, Japanese Patent Application Laid-open No. 63-208867 states that
In a developing method using a two-component developer consisting of a developing sleeve and toner, the formula (%) is used.
g/cm”), ρ is the true specific gravity of the developer (g/cm3), D
s is the distance between the developing sleeve and the electrostatic latent image recording member (am), and the developer filling rate (PD) of the developing section is 20 to 5.
It is described that variation in image density can be prevented by setting it to 0%.

(Problem to be Solved by the Invention) However, both of the former two proposals individually define the characteristics of the developer and the development conditions, and do not comprehensively capture the actual development operation. , and the characteristics of the developer and carrier are specified under static conditions and not under the dynamic conditions of the actual machine, so they do not necessarily correspond well to the actual developing method used in copying machines. It wasn't something that existed.

The latter proposal is considered to be significant as it focuses on the filling rate of developer in the developing section, but it is important to consider the contact state between the developer magnetic brush and the developing sleeve under actual developing conditions, that is, dynamic conditions. However, there was no regulation, and there was no good correspondence with the actual developing method used in copying machines.

The inventors of the present invention determined that during actual development, the contact between the developer magnetic brush and the photosensitive surface was fixed by fixing collodion to the magnetic brush, and then this was photographed using a scanning electron microscope. What you can easily know by:
And by setting the frequency (k) defined as the product of the number of carriers in contact per photoreceptor area (n pieces/mm2) measured in this way and the development length (L) to a certain range. It was found that high quality images can be obtained.

Further, the present inventors set the rotational speed of the developing sleeve, the rotational speed of the developing sleeve, and the magnetic flux density of the magnetic pole of the magnetic carrier in a specific relationship, and more preferably, in the contact state with the photosensitive surface during actual development. After fixing with a certain collodion, the number of carrier contacts per photoreceptor area (n, pieces/n + m2) measured by scanning electron micrograph and the developing length (
It has been found that high quality images can be obtained by setting the frequency (k) defined as the product of K and L) within a certain range.

The present invention was completed through repeated experiments based on these findings.

An object of the present invention is to provide a developing method in which when reproducing multiple fine lines, the line width of each line is constant, chipping at the leading edge and chipping at the trailing edge is prevented, and an image with high density and quality can be formed.

Another object of the present invention is to provide a developing method that has excellent reproducibility of Chinese characters and reproducibility when copying from copy to copy is repeated.

(Means for Solving the Problems) According to the present invention, a magnetic brush of an image characterized by setting a developing sleeve and toner is formed on the developing sleeve, and the magnetic brush is connected to a photoreceptor having a charge image. In the developing method of forming a sliding magnetic brush, the sliding between the magnetic brush and the photoreceptor is expressed by the following formula, k=L-n (1)
In the expression, H is the number of carrier contacts per photoconductor area (number/am') determined from a scanning electron micrograph of the collodion-fixed 6fl air brush, and L is the formula % formula % (2) (Nip is the number of carriers in contact with the developing sleeve. Developer nip width (m
m), and ■ is the movement of the developing sleeve L=Nip/V
d(Vs-■, is the moving speed of the developing sleeve (mm/se
c)) A developing method with excellent image reproducibility is provided, characterized in that the frequency (k) defined by is set to be 100 to 700. Ru.

According to the present invention, a developing method characterized in that a developing sleeve and toner are set, a magnetic brush of an image is formed on the developing sleeve, and this magnetic brush is formed into a sliding magnetic brush with a photoreceptor having a charged image. In the following formula % formula % (3) where f is the number of rotations of the developing sleeve (times/second), f represents the number of rotations of the developing sleeve (emu/g), and H is the saturation magnetization of the magnetic carrier. A developing method with excellent image reproducibility is provided, which is characterized in that developing conditions are set so as to satisfy (emu/g).

In the present invention, a developing method with excellent image reproducibility is characterized in that the above formula (3) is satisfied and the frequency (k) defined by the above formula (1) is set to be between 100 and 700. is provided.

In the present invention, it is preferable to use a developing sleeve having a rotational speed of 40 to 55 emu/g.

(Function) The present invention improves the contact frequency (k, number/mm) of carriers defined by the above formula (1) from 100 to 700, particularly 100.
This is based on the knowledge that when the number is set in the range of 300 to 300, the line width of each line is kept constant during development of dense fine lines, leading edge chipping and trailing chipping can be prevented, and a high quality copy image can be formed. .

Further, the present invention provides a characteristic value (m-
H/f) from 7,000 to 15,000, especially 9,00
When maintained in the range of 0 to 13.000, the line width of each line is kept constant during development of densely packed thin lines, preventing leading edge chipping and trailing edge chipping, and forms a high-quality copy image. This is based on the knowledge that it is possible.

In Figure 1, which is used to explain the leading edge chipping and trailing chipping that occur when developing dense fine lines, this graph shows the distance in the feeding direction on the horizontal axis, and the reflected image density measured by a microdensitometer of the dense fine line copy image on the vertical axis. The relationship between the two is plotted. Curve (1) in Figure 1 indicates that the line width for each line is constant and there is no chipping at the leading edge or trailing edge. Indicates that the edges are severely chipped. Regarding the reproduction of each line width, the deviation (δ) in the feeding direction is the image density of Toyama in the feeding direction, which is A and B in order.

When C, it is given by the formula % formula % (4). If the value of δ is 100 or around 100, each line width is constant and there is no deviation; if it is larger than 100, there is chipping at the tip; and if it is smaller than 100, there is chipping at the rear end. are shown respectively.

Figure 2 shows the contact frequency of the carrier (
k) and change the contact frequency (k) and line width deviation (δ)
This is a plot of the relationship between From the results shown in Figure 2, by selecting the contact frequency (k) within the above-mentioned range from among various development conditions and various developer combinations,
The surprising fact that line width deviation can be maintained close to 100% is revealed. In other words, as a general tendency, when the frequency of carrier (developer) contact is reduced, leading edge chipping (rear end thickening) appears, while when the contact frequency is increased, trailing end chipping (leading end thickening) tends to occur strongly. However, by selecting the frequency of contact within a certain range, both of these tendencies can be effectively prevented.

The carrier contact frequency (k) in the present invention is calculated by the above formula (
As shown in 1), it is expressed as the product of the number of carriers in contact per photoreceptor area n and the development length L, so by adjusting one or both of n and L, the setting can be made within a predetermined range. becomes possible.

FIG. 3 is a sketch of a scanning electron micrograph of a collodion-fixed magnetic brush for a two-component developer suitable for the present invention, from which the number of contacts per unit area can be easily measured.

The main factors that affect the number n of carriers in contact with each other per unit area are the physical properties of the developer, especially the developing sleeve, and the distance between the developing sleeve and the photoreceptor drum ff1li(do
-s). Generally, as dO-S increases, n decreases, and conversely, as do-5 decreases, n increases. do
Assuming that -5 is constant, n depends on the characteristics of the developer, especially the developing sleeve, especially on the saturation biling; as the rotational speed increases, n increases, and as the rotational speed decreases, n decreases.

Thus, the frequency of carrier contact (k) can be set by selecting the type of developer, especially the rotational speed of the developing sleeve. The number of revolutions of the BL carrier is 40.
By setting it in the range of 65 to 65 emu/g, the prevention of chipping at the leading end and chipping at the trailing end becomes even more perfect.

The development length in formula (2) has the following meaning. In FIG. 4, which schematically shows the developing section, the drum 1 has a circumferential speed of V.

The developing sleeves 2 are moving at a circumferential speed of Vs such that their moving directions become the same at the position of the nip width Nip. A magnetic brush of the developing sleeve 3 is formed on the developing sleeve 2.

On the developing sleeve 3, for example, minus 1i! :r
There is a toner 4 with 7a, while the carrier has a positive counter charge, and the toner 4 has an electrostatic latent image (
The counter charge on the carrier 3 escapes onto the developing sleeve 2 via the magnetic brush.

The nip passing time t of the latent image point is expressed by the following formula, and the length of the toner passing over the latent image point is the above t multiplied by the speed difference between the two, that is, expressed by the formula It turns out. This development length has a length dimension and is a value proportional to the amount of development toner. Thus,
It can be seen that the carrier contact frequency (k) can also be set by selecting the nip width (Nip), the drum peripheral speed (Vd), and the developing sleeve peripheral speed (VS).

Figures 5 and 6 show the relationship between line width deviation (δ) and mH/f and image density (1, D,) and m when the value of m -H/f is varied. -1(/f).These figures 2 and 3
From the results in the figure, it can be seen that by setting the m-H/f value within the range defined by the present invention, that is, within the range of 7000 to 15,000, the image density can be increased to 1.3 or more, and the line width deviation can be reduced. It becomes clear that it is possible to maintain close to 100%. That is, when the value of m - H/f is higher than the above range,
The reproducibility of line drawings is poor, r,<s, trailing edge chipping (tip thickening) occurs, and image density generally tends to decrease.On the other hand, when the m-H/f value is lower than the above range, the leading edge Not only does chipping (rear end thickening) occur, the image density also decreases, and carrier drag is also likely to occur.

Among the characteristic values expressed by the formula m-H/f, m-H of the molecule
is a value related to the centripetal force acting on the carrier, while f in the denominator is a value related to the centrifugal force acting on the carrier.Therefore, the ratio of the two is a dimensionless number, and is the difference between the centripetal force and the centrifugal force. This is a number related to balance. The range defined by the present invention is a range in which the centripetal force on the carrier is relatively small, and the carrier is in close contact with the latent image.
The influence of mechanical scraping on the toner image is small, resulting in a high-density image.The carrier has a large degree of freedom, which improves counter charge neutralization and diffusion, and the high electric field due to the edge effect makes it possible to create fine lines. The reproducibility is also expected to improve.

By setting the value within the above range and setting the carrier contact frequency (k, number/mm) defined by the above formula (1) in the range of 100 to 700, particularly 100 to 300, multiple thin wires can be formed. During reproduction, the line width of each line is kept constant while increasing the density of the image, preventing chipping at the leading edge and chipping at the trailing edge, and making it possible to form a high-density, high-quality image.

This also enables high-quality images to reproduce the kanji characters and the reproducibility when copying from copy to copy is repeated.

(Preferred Embodiment of the Invention) In FIG. 7 for explaining the magnetic brush development method used in the present invention, a large number of polar magnets 10. A magnet roll 11 having N and S magnets is housed in a developing sleeve 12 made of a non-6N material such as aluminum. There is a minute gap from this developing sleeve 12, that is, a distance of 1 eft d. -5, a photosensitive drum 15 consisting of a base 13 and an electrophotographic photosensitive layer 14 provided thereon is provided. The developing sleeve 12 and the photosensitive drum 15 are rotatably supported by a machine frame (not shown), and the moving directions (arrows) at the nip position are the same (the rotating directions are opposite to each other) and /J.
It is driven to The developing sleeve 12 is located at the opening of the developing device 16, and the developing device 16 contains a two-component developer (i.e., a mixture of toner and the developing sleeve).
18 d mixers 17 are provided, and a toner supply mechanism 20 for supplying toner 19 is provided above them.

The component-based developer 18 is mixed by the stirrer 17 to give the toner a triboelectric charge, and then supplied to the developing sleeve 12 to form a magnetic brush 21 on its surface. This magnetic brush 21
The panicle height is adjusted by the panicle cutting mechanism 22, and the panicle is conveyed to the nip position with the electrophotographic photosensitive layer 14, where it is left standing on the photosensitive layer 14.
The W image is developed with toner 19 to form a visible image.

According to the present invention, the carrier contact frequency (
k) is set within the range described above.

According to another aspect of the present invention, the magnetic flux density of the magnetic pole located in the developing section is H%, and the rotational speed m of the developing sleeve and the rotational speed f of the developing sleeve are set within a range that satisfies the above formula (3).

Furthermore, according to another aspect of the present invention, while satisfying the above formula (3), the contact frequency (k) of the carrier in the above formula (1) is preferably set to be within the above range.

This setting is not limited to the following description, but is, for example, as follows.

When the rotational speed of the developing sleeve is small, the ratio of m - H / f becomes small, and the number of carriers in contact with each photoconductor area decreases, and the contact frequency (k) tends to decrease accordingly. Yes, and if reversed, the trend would be opposite to the above. The rotation speed of the carrier is 40 to 65 emu/g, especially 45
It is desirable that the amount is in the range of 56 emu/g to 56 emu/g. The developing sleeve is a ferrite carrier that satisfies the above conditions.
Particularly preferred are spherical ferrite carriers, the particle size of which is from 20 to 140 μm, especially from 50 to 100 μm.
It is desirable that it be within the range of .

Conventionally, ferrite has been used, for example, iron zinc oxide (ZnFe2
0. ), iron yttrium oxide (Y3F-5012), iron caddolinium oxide (CdFezOJ, iron gadolinium oxide (Gd3Fe50+2), iron copper oxide (GuFe204)
, iron oxide complex (PbFe+20+9), iron oxide nickel) L
t (NiFe204), neodymium iron oxide (NdF
e03), barium iron oxide (BaFe+zO+9),
Magnesium iron oxide (MgFe204), manganese iron oxide (MnFe204), lanthanum iron oxide (LaFe03)
) etc. 1f! ! Alternatively, sintered ferrite particles with a composition consisting of two or more types are used, especially Cu, Zn, M
Soft ferrites containing at least one, preferably two or more metal components selected from the group consisting of g, Mn and Ni are used, such as copper-zinc-magnesium ferrites, among these ferrites,
Use one that satisfies the above conditions.

The electrical resistance of a ferrite carrier varies not only depending on its chemical composition, but also on its particle structure, manufacturing method, and coating type and thickness. Generally, its volume resistivity is between 1X10” and 5X10
"Ω・Cff1, especially 4 X 10" to lXl0"Ω
・It is best to be within the cm range.

The toner used in the present invention is one in which a colorant and a charge control agent, or further toner ingredients known per se, are blended in a fixing resin medium. The toner used in the present invention is 1X10' to 3X109Ω.
cm, particularly 2 x 10'' to 8 x lO' Ωcm, and its dielectric constant is preferably 2.
It is preferably in the range of 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 is, in the following formula, R3 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, a halogen atom, etc. is a substituent, and n is 2 including zero.
Examples of monomers represented by the following integers include styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene, vinylxylene, and vinylnaphthalene.

Among these, styrene is preferred.

On the other hand, as an acrylic monomer, 3 -〇 -I+ 4 In the formula, R5 is a hydrogen atom or a lower alkyl group, and R
4 is a hydrogen atom or an alkyl group having up to 18 carbon atoms, monomers represented by, for example, ethyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, acrylic acids, 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 (8) and the acrylic monomer (B) are A:B=50:5.
0 to 90:10. Especially 60:40 to 85:t5
It is recommended that the range be within the range of . In addition, the resin used is generally 0
It is preferable to have an acid value of 25 to 25. Further, from the viewpoint of fixing properties, it is preferable that the toner has 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 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: 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 black (CI26150), and Subiron black, and 1:1 type or 2:1 type metals. complex 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 (particularly 10 μm) as a volume-based median particle size measured with a Coulter counter.
The particle size is preferably in the range of 12 μm to 12 μm, and the particle size may be amorphous particles produced by a melt-kneading/pulverization method, or spherical particles produced by a dispersion or suspension polymerization method.

The mixing ratio of the toner and the developing sleeve varies depending on the physical properties of the toner and the developing sleeve, 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 . Furthermore, the electrical resistivity of the developer as a whole is 5 x 109 to 5 x 101.
0Ω-cm, especially lXl0” to 4X to 10Ω・
cm range is preferred for the purposes of the present invention.

In the developer of the present invention, the number of carriers in contact with each photoreceptor area is generally in the range of 100 to 30,000 mm2, particularly preferably in the range of 100 to 20,000 mm''.

The development length L expressed by the above equation (2) is related to the contact frequency k and also to the image density.

In the present invention, the development length L is 4 to 35n+m.

In particular, the nip width (NIp) should be between 4 and 20 mm.
and developing sleeve circumferential speed (VS), and drum circumferential speed (
Vd).

Among these, the developing nip width (Nip) is generally 1 to 15
+nm, particularly preferably in the range of 2 to 8 mm.

Also, the distance l between the developing sleeve and the photosensitive layer! ! We have already pointed out that tdo-s has an important influence on n, but dO-
S is generally 0.5 to 3, 0m+n, especially 0.7
The range is preferably from 1.7 m+a to 1.7 m+a.

The magnetic pole of the magnetic carrier should preferably have a relatively low magnetic flux density as long as it does not cause carrier attraction, generally 400 to 1500 Gauss, particularly 550 to 900 Gauss. It is also effective to make the rotation speed of the developing sleeve relatively high, and generally a range of 1.50 to 5.00 rotations/second is appropriate, although it depends on the sleeve diameter.

As the photoreceptor, photoreceptors conventionally used in electrophotography, such as selenium photoreceptors, amorphous silicon photoreceptors, zinc oxide photoreceptors, cadmium selenide photoreceptors, cadmium sulfide photoreceptors, various organic photoreceptors, etc. are all used.

As another development condition, the bias voltage applied between the developing sleeve and the photoreceptor conductive substrate has an average electric field strength of 10
0 to 1000V/+n+a, especially 125 to 500V
/[0111 range is preferable.

The resistivity and dielectric constant of the toner used in the present invention were measured using a parallel plate electrode type measuring device with an electrode area of 2.27c+n2 and an inter-electrode distance of 0.5 mm, and the toner was filled to a porosity of 25%. The vehicle peak was measured by applying an AC voltage of +IV to -1V.

Further, the electrical resistivity of the keys and rears used in the present invention was measured using the measuring device shown in FIG. 8 by the following method. That is, as shown in FIG.
1, the carrier 33 is carried on a sleeve 34, and the carrier 33 is conveyed with the layer of the carrier 33 adjusted to a predetermined thickness by a spike regulating member 35. Further, a detection section 38 having a predetermined surface area is disposed with a micrometer 37 as an inter-electrode distance adjusting means along an imaginary line 36 on the surface of the photoconductor facing the sleeve 34 with a predetermined distance, While conveying the carrier 33 together with the sleeve 34,
An alternating current voltage of a predetermined frequency is applied to the sleeve 34, the detection signal y from the detection section 38 is supplied to a parallel circuit of the dummy and the oscilloscope 39, and the waveform data on the oscilloscope 39 is read by the reading means 40, and the calculation section 41, the electrical resistivity was calculated.

In the figure, reference numeral 42 is a cleaning blade serving as a cleaning means for removing the carrier 33 remaining on the sleeve 34.

In measuring the dielectric constant using the above measuring device,
The distance between the sleeve 34 and the detection section 38, that is, the distance between the electrodes d = 1.2 + nl11. The surface area of the detection unit 38,
That is, the electrode area S was set to 0.785 cm2, and an AC voltage with a frequency of 50 Hz was applied.

In addition, the layer thickness of the carrier 33 supported by the sleeve 34 can be adjusted by the spike control member 35 to set the filling rate of the carrier to about 15 to 50%.

(Effect of the invention) According to the present invention, the 6i1 that actually contacts the developing sleeve
Frequency of carrier contact (k) defined as the product of the number of carrier contacts per photoreceptor area, determined by fixing the air brush with collodion and measuring with an electron microscope, and the development length.
According to the present invention, the value of m-H/f, that is, the degree of balance between the centripetal force and the centrifugal force acting on the developing sleeve, can be set to a certain range, that is, in the range of 100 to 700. Furthermore, according to the present invention, the value of m-H/f is preferably set in the range of 7,000 to 15,000. and carrier contact frequency (k) from 100 to 700 above.
By setting within the range of , when reproducing multiple thin lines, the line width of each line is kept constant while increasing the image density.
It has become possible to prevent leading edge chipping and trailing chipping, and to form images with high density and high quality. This also makes it possible to provide a copying method with excellent reproducibility of kanji.

(Experiment example) Hereinafter, the present invention will be explained in more detail using experimental examples.

Experimental Example 1 Using a modified electrophotographic copying machine D C-2585 (manufactured by Sanda Kogyo Co., Ltd., trade name), three types of developers with the physical properties shown in Table 1 were used, and the developing conditions (photoconductor tram - developing sleeve amount ratio) were used. 11iD
-3, Developing sleeve-photosensitive drum circumferential speed ratio V s/V
d) was changed, the frequency (k) was measured, and the image quality at this time (image density (1, D), bias of dense thin lines (δ)) was measured. Incidentally, the developing tip gap is 1.0 [n+ml,
The main charging developing sleeve potential was 800 [V]. The results are shown in Table-2.

From Table 2, it can be seen that when the frequency (k) is in the range of 100 to 700, good results are obtained in both image density (1, D) and bias (δ). In particular, Test Examples 1 and 3 had particularly excellent high quality images with a score of 9,429.

In addition, in Test Examples 6 to 11, the frequency (k) was either that the image density was satisfactory but the unevenness of fine lines was poor, or even though the unevenness of fine lines was satisfactory, the image density was low.
is less than 100 or greater than 700-H, and the value of □ is also less than 7,000 or greater than 15,000.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between distance in the feeding direction and green density of dense thin lines, FIG. 2 is a diagram showing the relationship between contact frequency and line width deviation, and FIG. 3 is a diagram showing the relationship between contact frequency and line width deviation. To measure the number of contacts per unit area,
A sketch of a scanning electron micrograph of a collodion-fixed magnetic brush is shown, FIG. 4 is a diagram schematically showing a developing section, and -H FIG. FIG. 7 is a diagram for explaining a magnetic brush development method, and FIG. 8 is a diagram for explaining a method for measuring the electrical resistivity of a carrier used in the present invention. FIG. Figure 7

Claims (4)

[Claims] (1) A developing method in which a magnetic brush of a two-component developer containing a magnetic carrier and toner is formed on a developing sleeve, and this magnetic brush is rubbed against a photoreceptor having a charge image to form a toner image. , The sliding friction between the magnetic brush and the photoconductor is expressed by the following formula: k=L・n In the formula, n is the number of carriers in contact per photoconductor area (carriers/mm ^2), and L is the formula L=Nip/V_d(V_s-V_d) [Nip is the nip width (mm) of the developer on the surface of the photoreceptor.
), and V_s is the moving speed of the developing sleeve (mm/s
ec), and V_d is the moving speed of the photoreceptor surface (mm/
1. A developing method with excellent image reproducibility, characterized in that the frequency (k) defined by the following formula is set to be from 100 to 700, indicating the development length defined by: sec). (2) A developing method in which a magnetic brush of a two-component developer containing a magnetic carrier and toner is formed on a developing sleeve, and this magnetic brush is rubbed against a photoreceptor having a charge image to form a toner image. , In the following formula 15,000≧(m・H)/f≧7,000, f represents the number of rotations (times/second) of the developing sleeve, and m represents the saturation magnetization (emu/g) of the magnetic carrier. , H represents the magnetic flux density (Gauss) of the magnetic pole in the developing sleeve. (3) A developing method in which a magnetic brush of a two-component developer containing a magnetic carrier and toner is formed on a developing sleeve, and this magnetic brush is rubbed against a photoreceptor having a charged image to form a toner image. , In the following formula 15,000≧(m・H)/f≧7,000, f represents the number of rotations (times/second) of the developing sleeve, and m represents the saturation magnetization (emu/g) of the magnetic carrier. , H represents the magnetic flux density (Gauss) of the magnetic pole in the developing sleeve, and satisfies the following formula k=L・n, where n is the collodion fixed magnetic brush per photoreceptor area obtained from a scanning electron micrograph. It is the number of carriers in contact (pieces/mm^2), and L is the formula L=Nip/V_d(V_s-V_d) [Nip is the nip width of the developer on the surface of the photoreceptor (mm
), and V_s is the moving speed of the developing sleeve (mm/s
ec), and V_d is the moving speed of the photoreceptor surface (mm/
A developing method with excellent image reproducibility, characterized in that developing conditions are set so that the frequency (k) defined by is 100 to 700, and the developing length is defined as 100 to 700. . (4) Saturation magnetization as a magnetic carrier is 40 to 65 em
4. A developing method with excellent image reproducibility according to claim 1, 2 or 3, wherein a magnetic carrier of u/g is used.