JPS5868051A - Developing method - Google Patents

Abstract

PURPOSE:To enhance fixability of toner, and to enable use of color toner by using a developer obtained by mixing the toner with specified powder, and developing a latent image without bringing a developer-holding body into contact with an image-bearing body. CONSTITUTION:An insulating toner is mixed with a conductive magnetic powder to form a developer 9, and this is fed to a developing sleeve 5, the sleeve 5 is coated with the developer 9 with a magnetic blade 7 to a thickness smaller than a space between the sleeve 5 and an image-bearing body (photosensitive drum)4. This developer layer is moved to a developing position, and transferred to the drum 4 across the space to develop the image. At that time, low frequency alternating voltage is applied between the sleeve 5 and the drum 4 from a power supply 11 to form a good image.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing method for developing an electrostatic latent image.

The present applicant previously filed Japanese Patent Application Laid-open Nos. 54-18656 to 18659.
The publication discloses a new developing method. In this method, an insulating magnetic toner is uniformly applied onto a cylindrical development tension support member having a magnet inside, and the toner is brought into contact with a latent image holding member and is opposed to the latent image holding member for development.

At this time, a low frequency alternating voltage is applied between the developer support member and the base conductor of the latent image holding member, and the toner is moved back and forth between the developer support member and the latent image holding member, thereby eliminating the soil force. It is possible to perform good development without any thinning of the four images, and with excellent gradation reproduction. In this developing method, since the toner is an insulator, transfer is easy. Furthermore, the developing device is extremely simple and inexpensive.

However, this developing method had the following drawbacks because it required the use of magnetic toner.Magnetic toner generally contains black astringent powder, so it cannot be used for colors other than black. It is difficult to make colored toners.Also, by including magnetic powder, the toner image has poor layer stability when fixed by heat setting, pressure setting, etc.
Coating 74 toner with 3° magnetism on the developer support member f = t
L, hold this still as 1 image i'J< (opposite O -C
The method of developing has been known for a long time. However, the problem is that it is difficult to apply toner uniformly to the raw material support member, and that electrostatic
It has not been put into practical use due to its own shortcomings, such as the sloppy nature of the drawings and the poor recitation of the current 1 family and 1 image.

One component l)4. Because of these drawbacks of the image method, conventionally, when developing beads using color toner, it has been common to use a two-component developer containing a mixture of toner and carrier. However, with the two-component development system, the gear rear deteriorates, the toner and gear rear must be kept at a constant ratio, which is difficult to control, and the developing device is large and complicated. ) has the following disadvantages.

The present invention aims to eliminate the above-mentioned drawbacks of conventional developing methods, and is used in the developing method disclosed in 7', such as a developer. My father can use the same thing as the cursed image device, or something with a similar configuration. The developer contains a small amount of carrier, but this is mostly consumed.1. There is no damage or deterioration.

However, there is a wide range of mixing ratios between toner and carrier.

The developing method of the present invention uses an insulating toner and a conductive 'LA'. Mix fine powders with different properties.

The developer support member -F having a magnet on its back surface is uniformly coated with the developer support member -F, and the developer is developed by facing the latent image holding portion IA without coming into contact with it. At this time, a good image can be obtained by applying a low frequency alternating voltage between the developer supporting member and the latent image holding member.

Iron oxide powder, etc. can be used as the powder that has conductivity and magnetism, but known conductive materials obtained by melting and mixing a magnetic material and resin, pulverizing the mixture, and treating it with conductivity with carbon, etc. The same magnetic toner is more preferably used, for example, as disclosed in Japanese Patent Application Laid-Open No. 54-43
As described in No. 037, a blade made of a magnetic material is arranged opposite to the magnetic pole of a magnetic field generating means installed in a developer support member, and a toner layer thinner than the gap between the blade and the support part is cut by magnetic cutting. It is possible to form. Generally speaking, it is difficult to uniformly apply a non-magnetic toner to the developer support portion, but in the method of the present invention, the toner is attached to the magnetic gearia and the cooled developer layer is extremely difficult to apply. There are many cases where the toner is in direct contact with the developer support member, blade, etc. Therefore, the frictional charging properties of the carrier powder are more important, and good images can be obtained if the toner itself has excellent triboelectric charging properties. Therefore, there is almost no deterioration in image quality due to deterioration of the carrier, which occurs in conventional two-component development systems.

Current IS! The developer is supported by a magnet installed in the developer support member and opposed to the latent image retention member while the toner and gear are still mixed. As a result, the developer jumps to the latent image holding parts A and J due to the electrostatic force of the latent image and the low frequency alternating voltage applied between the developer supporting member and the latent image holding member.
It performs reciprocating motion according to the alternation IF.

The principle of this reciprocating movement of the developer will be explained below using FIGS. 1 and 2 as examples. As shown in the figure, there are four voltage waveforms applied to the toner carrier in the lower part, which are rectangular waves here, but the waveforms are not limited to this as will be described later. A negative polarity bar of magnitude Vmin in time interval t1.
[When Asdeno is applied, the magnitude v at the time interval t2
A max positive polarity bias' release pressure is applied. Vm
in.

The size of Vmax is 1i? When developing with charged toner, the image area potential is VD, and when the non-image area potential is VL, Vmin < VL < Vn < Vmax.
・・・・・・・・・・・・・・・Choose to satisfy (1). If you choose like this, the time interval 1. The bias voltage Vmin acts to provide a bias voltage that tends to promote toner adhesion to the image and non-image areas of the electrostatic latent image carrier, and is therefore referred to as the toner transfer stage. The time interval taf is called a toner reverse transfer stage because the bias migration Mnax acts to give a direct bias increase to the tendency of the toner transferred to the latent image holding surface to be returned to the toner carrier during the time interval.

Vth・f and Vth・r in FIG. 1 are from the toner carrier, respectively? This is the potential threshold at which the toner transfers to the image-permitting surface and from the latent image surface to the toner carrier. think. , In the upper part of Figure 1, t
The toner transition at 1 and the degree of toner reverse transition at 12 are plotted as a model against the image potential at a.

At the toner transfer stage, the amount of toner transferred from the book to the electrostatic image holder is as shown in Fig. 1. The slope of this curve is approximately equal to the slope of the curve when no alternating bias voltage is applied. At this time, the toner transfer amount tends to be saturated and discontinued at a value intermediate between VL and VD, and therefore the reproduction of halftones is inferior, and the lv tonality is R&D. .

The second broken line curve 2 shown in FIG. 1 represents the probability of the degree of toner reversal.

In the developing method according to the present invention, such a toner transfer stage and a toner reverse transfer stage are alternately repeated to give an alternating eccentricity as shown in Figure 1, and the bias phase 1 of the toner transfer stage of the alternating electric field , let the toner from the toner support reach the non-image area of the electrostatically deposited image carrier (of course it also reaches the image area), and the bright area potential (VT, )
In order to improve the gradation by sufficiently adhering the toner even to the half-tone potential portion which has a cold potential, the bias phase (tl) of the toner reverse transition stage is applied in the toner transfer direction. By applying a bias in the opposite direction, the toner that has reached the non-image area as described above is returned to the original toner support side.In this toner reverse transfer stage, as will be described later, the toner that has reached the non-image area is returned to the original toner support side. Since the image area originally has no image potential, when a bias electric field of opposite polarity is applied, the toner that has reached the non-1Ii11111! area immediately leaves the non-image area and is transferred to the toner carrier. On the other hand, since the toner once attached to the image area including the halftone area is attracted to the image area'd load, the above-mentioned gravitational force acts in the opposite direction to this gravitational force. Even if a reverse bias is applied, there are few stitches in which the image actually leaves the image H1≦ and returns to the toner support side.In this way, bias electric fields of mutually different polarities are alternated with a preferred amplitude and frequency. By causing the above-mentioned toner transfer and countertransference to occur many times,
Repeated at development position. In this way, the amount of toner transferred to the latent image surface can be made faithful to the potential of the static image. That is, as the toner transfer J[n is shown as curve 3 in FIG. Therefore, in the non-image area, there is virtually no toner adhesion in the end, while toner adhesion to the halftone image area is an excellent visualization with extremely high gradation in accordance with the surface potential. This tendency can be solved by setting the gap between the electrostatic image carrier and the toner support to become narrower toward the end of the development process, and reducing the above-mentioned electric field during the development interval. By reducing the intensity and converging it becomes -I reactor manifestation.

An example of such a developing process according to the present invention is shown in the 21st case.・As shown in Figure 2 (Δ) and (B),
The electrostatic image holder 4 moves in the direction of the arrow, and during this period passes through the development 1 pursuit areas (2) and (2) and reaches (2). 5 is a toner carrier. Therefore, the gap between the electrostatic image holding surface and the toner carrier gradually widens starting from the closest position in the developing section. (A) shows the electric field of the image area of the electrostatic image carrier, and (B) shows the electric field of the transfer and countertransition from the toner carrier in the non-image area. In addition, the figure (C) shows the voltage applied to the toner carrier. 7- Indicates the waveform of 't's pressure, and when the electrostatic image charge is positive, 1 ■ maX - ■ I, l > l VI, -Vmin
l, l Vmax - VD l (l VD - Vmi
n l...(2) is set.

The first process in development occurs in the head loading ■, and the second process occurs in the area Q).
process is occurring. In the case of the image area shown in FIG. 2(A), in region (2), both toner transfer and countertransference occur alternately depending on the phase of the alternating current electric field. As the development gap becomes larger, both the transition and reverse transition electric fields become weaker in (2), and although toner transfer is possible, the reverse transition electric field is no longer strong enough to cause reverse transition (below the I state value). ■Then, the earliest transition,
No backtransference occurs and the development is completed.

In the case of the non-image area shown in FIG. 2(B), both toner transfer and countertransference occur in the area.

Therefore, soil failure occurs in this area. In case (2), both the transfer and countertransference electric fields become weak, and although the toner countertransference has 0T ability, the transfer electric field (below the threshold value) sufficient to cause the transition disappears. Therefore, soil strain burrs do not substantially occur in this area, and soil strain burrs that have occurred are also removed. In case (2), neither transfer nor countertransference occurs anymore, and development is completed. For halftone image areas, the final toner transfer to the latent image surface is determined by the toner transfer sleeve depending on the potential and the amount of reverse transfer.
In the end, the curve is small, like curve 3 in Figure 1.

Therefore, a visible image with high gradation can be obtained.

In this way, the toner is flown through the development gap and once reaches the non-image area to improve the gradation, and then the non-image area is
In order to have the effect of mainly stripping off the adhered toner, it is necessary to appropriately select the amplitude of the applied alternating bias '+4L ratio and the alternating frequency.

Although reciprocating movement of the developer occurs between the toner carrier and the electrostatic image holder in this way, the details of this process have not yet been fully elucidated. In the present invention, the carrier in the developer and the toner both fly and travel, but remain on the mochibe. It is presumed that this is because the carrier particles are electrically conductive. Toner, which is an insulator and has a charge, does not easily separate when it adheres to the image area of an electrostatic image. However, in the process of conductive particles jumping from the developer support member to the latent image holding member, charge is injected from the developer support member, but the electrostatic image image [when it comes into contact with the step part]
It is easily neutralized by the charge of the electrostatic image, and in some cases its polarity is reversed, and it jumps to the developer support member and is separated.

In this way, since 4-character particles do not exhibit strong adhesion,
Finally, it is held by the developer supporting member by 1° by magnetic force. Therefore, there will ultimately be no green lubricant on the electrostatic image holding member.
・A visible image is formed only by the ner.

In the development method of the present invention, the electrostatic properties are not so important as they are necessary for the carrier particles.

Therefore, the mixing ratio of toner and carrier is relatively free.

Furthermore, if there is a predetermined amount of carrier particles on the developer support member-L, the carrier particles will not separate from the developer support member, so it is only necessary to replenish toner.

〔Example〕

Experiments were conducted using the developing apparatus shown in FIG. In the illustrated apparatus, 4 is an electrostatic image carrier having an electrostatic latent image obtained by a known electrophotographic method. Reference numeral 5 designates a developing sleeve as a non-magnetic developer carrier having a fixed magnet roll 6 therein. In the developing section, a magnetic pole (for example, the S pole shown in the figure, approximately 650 Gauss) is disposed inside a developing sleeve 5 facing the electrostatic image holding member 4, and the distance between the developing sleeve 5 and the electrostatic image holding member 4 is as follows. These are both ends of the sleeve, and regulate the developer 9 of the present invention in the hopper 8 to a desired thickness. The toner is mainly triboelectrically charged between it and the developing sleeve 5. A developing sleeve 5 is placed opposite the blade 7 made of a magnetic material or a magnet.
One magnetic pole of the magnet roll 6 (for example, in the illustrated example, an Nl pole of 850 Gauss) is arranged inside the magnet roll. In this case, the developing sleeve 5 and the blade 7 made of this magnetic material
The thickness of the layer of the developer 9 of the present invention in the developing sleeve 5 is regulated by the magnetic field between the blade 7 made of a magnetic material and the developing sleeve 5. The direction of rotation of the developing sleeve 5 is the same as the direction of rotation of the photoreceptor, as shown in the figure. In the figure, 10 is a scraper blade for scraping off the residual developer on the sleeve 5.
Reference numeral 11 denotes a power source for forming an alternating electric field between the sleeve 5 and the photosensitive drum 4, and generates a pulse wave, an alternating current, a voltage obtained by superimposing an alternating current with a direct current, or the like. In this example 1000
A power source was used in which a +200 V direct current was superimposed on a Vp-p alternating current.Incidentally, the latent image potential on the photosensitive drum 4 was +500 in the image area and 0 in the non-image area.

The toner used was as follows.

After mixing and pulverizing with a η mill on a μ surface, melt-kneading 1 volume with a roll mill, and after cooling, coarsely pulverize with a no-mer mill.
Next, it is pulverized using an air jet type pulverizer. The obtained finely pulverized product was classified to select 5 to 20 pieces, and the powder was used as a toner. This is a magenta color toner.

The carriers I used were: (1) Minolta Shashin EGIOI Copying Toner (2)
1T of SF 730 copy stand toner manufactured by Sharp Corporation
The toner was melt-kneaded, crushed and classified in the same manner as the toner described in J, and 4 tons of carbon black was added to the resulting body and treated in hot air.

Although the above three types were used, no significant differences were found between them. In the following description of the experiment, these three types of developer will not be particularly distinguished.

Of these three types, developer (2) has a relatively high resistance and has a resistance of 10
Under an electric field of 000 V/cm, the resistance was 109 Ωα. However, it cannot be said to have a high enough resistance to hold an electrostatic charge, and is considered conductive.

The developer in (3) is under an electric field of 0OOV/cT11 f
10'Q+m The following is the same measurement method →=lV, Ax
Under an electric field of 1013, the resistance value exceeded Ωa and could not be measured.

When the above toner and carrier were mixed and used as a developer, the mixing ratio of toner and carrier was 】:4
When the ratio was between 1:1 and 1:1, a fairly good image was obtained, but some unevenness was observed in the developer layer on the developer supporting member, resulting in slight unevenness in the image.

Therefore, the scraper 10 was replaced with a scraper 7, and the developer support member was replaced with a support member whose surface was roughened as described in Japanese Patent Application No. 16453/1983, which was previously proposed by the present applicant. As a result, a good image without unevenness was obtained.

Here, approximately the same amount of toner as the developer in the developer was added to the popper, and a good image was obtained as well. this is,
The carrier particles on the developer support member are attracted to the developer support member by magnetic force, and are not mixed with the newly added toner in the hopper, but only the required amount of toner in the hopper adheres to the carrier particles. It's for a reason. In any of these cases, no gear particles were observed to adhere to the latent image holding member.

When the bias voltage applied to the developing device was turned off and the developing device was grounded, development was possible. However, the image quality was inferior to that with bias added.

In addition to the above-mentioned examples, the carrier particles are also used in ordinary two-component magnetic brush development. Although iron powder (particle size: about 50 to 100 μm) whose surface was nitrided was used, a satisfactory image could not be obtained. This is believed to be because the carrier particles have a large particle size and are likely to be insufficiently mixed with the toner particles. Further, when magnetite powder (particle size is approximately 0.2 μm) was used, the developed image contained a large amount of carrier particles. This seems to be because the particle size is too small compared to the toner particles, and the toner particles and carrier particles are not sufficiently separated during the development process. The size of toner particles and carrier particles are relatively close to each other.
) Horrible. According to experiments, the size ratio of the two is 1:3.
If it is within the range, it is good. In this case, either the toner particles or the carrier particles may be large.

As described in detail above, in the present invention, an insulating υ' toner and a small powder having conductive properties are mixed, and this is placed on a developer support part having one stone on the surface. Since the toner is uniformly applied and developed by facing the latent image holding member without contacting it, the consistency of the toner is good and color toner can also be used.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of the characteristics of the toner transfer amount and toner reverse transfer degree with respect to the m image potential, and the applied voltage waveform.
Figures (A) to (q are process explanatory diagrams schematically showing the movement of developer and the applied voltage waveform in the process of the developing method according to the present invention, and Figure 3 is a cross section of a developing device showing an embodiment of the present invention. In the figure, 4... Electrostatic image holder, 5..., 1. Imaging sleeve, 6. Fixed magnet roll, 7. Magnetic blade, 8. Hopper, 9. ...phenomenon, 1
0...Scraper, 11...Bias honey O'A,
k represents. Applicants: 70 Canon-I Shujikai companies! +, condition

Claims (1)

[Claims] (1) A developer containing a mixture of insulating toner and conductive and magnetic powder is supplied to a developer supporter, and the developer is transferred onto the developer supporter by a developer regulating means at a developer position. The toner is applied in a layer thinner than the distance between the carrier and the image carrier, this developer layer is transported to a development position, and at the development position, the toner is transferred to the image carrier through a gap to perform development. A developing method. +2) The developing method according to claim 1, characterized in that an alternating electric field is applied to the gap between the developer carrier f and the image carrier.