DE3411655A1 - Development of electrostatic or magnetic latent image - Google Patents

Abstract

Development process involves (a) applying a developer contg. carrier and toner particles to a developer transfer carrier (I) to form a developer layer (II); (b) introducing (II) into an oscillating electric field; and (c) developing a latent image produced on an image carrier (III) with the developer in the oscillating electric field.

Description

-1-

Development process

The invention relates to a development method for Transferring one to an image carrier or receiver an electrostatic recorder such as an electrophotographic duplicator electrostatic image or charge image into a visible image or to convert a magnetic one Image into a visible image.

The following is first the duplication process briefly exemplified in an electrophotographic duplicating machine.

For example, in an electrophotographic duplicating machine With a template carrier made of glass, a template to be reproduced is first placed on the template carrier hung up, after which a duplicate or copy key is pressed; then one gropes Exposure lamp from the original while it illuminates it and thereby a predetermined relationship to a optical system with reflecting mirror and the like. The light reflected according to the density of the original is picked up by the optical system Thrown an image recorder or carrier (photosensitive drum) that is evenly charged electrically is, so that an electrostatic or charge image is created on this image carrier or this drum. The-

This is then carried out using a developing device With the help of a toner developed into a visible image according to the original density.

B On the other hand, it becomes a duplicating or copying paper (Transfer material) from a paper feed unit in synchronism with the rotation of the photosensitive Drum fed and then in accordance with the toner image formed on the drum brought, whereupon the toner image is transferred to the copy paper by means of a transfer electrode. Afterward the copy paper is separated from the drum and transferred to a roller fixing device. The latter consists of two rollers, at least one of which is heated, and is used for heating and fixing of the toner image transferred onto the copy paper. Finally, the copy paper (the finished copy) discharged from the housing of the device.

The developers used for the described process · » They include a two-component developer and a one-component developer. The former consists of one Toner in the form of coloring particles and a carrier that is used for electrically charging the toner and for its transfer to a development unit is necessary, while the one-component developer mainly consists of coloring particles of a uniform structure of a synthetic resin and a magnetic substance.

As the developing method using a developer containing a magnetic substance, is general a magnetic brush development process is known. This is briefly explained below.

A developer carrier in which a fixed

-3-

standing or rotating magnetic roller is installed, is arranged in the vicinity of a photosensitive element. The developer is brought into sufficient contact with a portion of this transfer carrier. If the magnetic roller and / or the developer transfer rotate more stubbornly, this forms on the outer surface a sleeve (cylinder), a pile (ear) of the developer, and this "developer becomes a developing unit transferred through which it is brought into contact with the photosensitive element.

The toner particles are attracted to the charged γ, part of the photosensitive element, so that

a visible image is generated on the latter by the toner particles.

15th

The magnetic brush developing method using the one-component developer has had a problem that the toner particles cannot be easily charged by friction and that the toner particles tend to clump together. For this reason, the toner particles are temporarily not sufficiently attached to the charged part of the photosensitive member. This problem does not occur when using .des Zweikomponeptenent-, '■ 25 winder on ,, rather it can do e-

ot
/ d

7fhneibysc

S) ηtfrfrohο T \ f μ nd the frictional properties of the r with respect to the photosensitive element are excellent. In addition, the brush ensures a sufficient cleaning effect when used for cleaning purposes. As a result, the two-component developer has found widespread use, although it requires adjustment of the amount of toner particles with respect to the carrier particles. In this development method, a developer is generally used which is composed of magnetic

-4-

tables carrier particles of a particle size corresponding to a multiple of 10 μπι to a multiple of 100 μm and non-magnetic toner particles eii; er particle size corresponding to a multiple of IO um. Since both the toner particles and the carrier particles are quite large, this occurs Procedure Possibly the problem is that there is a high quality image reproduction of fine lines or dots or fine gradations of density can not easily be achieved. To follow this development process a Various improvements have been sought to achieve a high quality image, such as a synthetic resin coating of the carrier particles, an improvement of a magnetic substance in the developer-transfer carrier (developer transfer support), the application of a bias voltage to this transfer carrier, etc., but it has been proven these procedures prove to be not entirely satisfactory and sufficient to provide an image high quality not fully suitable. It can therefore be assumed that the particle size of the toner and Carrier particles are further reduced in size so that carbon black is obtained when a reproduced or copied image of high quality is obtained shall be.

When the toner particles have a particle size of up to 20 µm, and especially up to 10 µm, occur the following problems:

1. During the development, the influence of the van emerges the Waals forces to the Coulomb force, with a so-called. "Obfuscation" occurs at which Toner particles build up in the background part of the image. This obfuscation can also be passed through biasing the developer / transfer carrier by means of a direct voltage is not easy impede.

-δ-2. Control of the frictional charging of the toner particles becomes difficult, and no clumping of the toner particles is expected with any probability; when the particle size of the toner particles is further reduced,

3. In this way, the carrier particles attach to the charge image part of the image carrier.

It is believed that these phenomena are due to the fact that the bias force decreases and the carrier particles are attached to the image carrier together with the toner particles. If the If the bias voltage is increased, the carrier particles also attach to the base part or background of the image.

When the particle size is reduced, the undesirable effects described above increase Side effects so that a clear or sharp image cannot be obtained. For this reason it has s: \ ch has been found to be difficult in practice to reduce the particle size of the toner and the carrier.

The object of the invention is thus to create an improved development process, which even then is not has had the above-mentioned problems of the prior art when one of fine carrier particles existing developer, in particular a developer composed of a mixture of magnetic carrier particles and toner particles.

The solution to this problem results from the measures characterized in the attached claims.

The invention thus provides a development process which is characterized in that a developer containing carrier particles and toner particles is added a developer transfer medium to form a Layer is transferred, the developer layer is introduced into an oscillating electric field and a Latent image from an image carrier by means of; Developer is developed in the oscillating electric field.

When developing a (latent) image on an image carrier by transferring a developer from carrier particles, in particular one from essentially a mixture of magnetic carrier particles and toner particles, to form a developer-transfer carrier, wherein at least the toner particles contained in the developer between the developer transfer carrier and the image carrier opposite this can be caused to vibrate by means of an oscillator, the specified The object of the invention can be achieved with a development process in which the mean particle size of the carrier particles is in the range of 5-50 µm, preferably up to 30 µm, and the mean particle size of the toner particles up to 20 µm, preferably up to 10 µm. The term "mean particle size" refers to the mean value of the diameters of the Particle (number average of major and minor axes).

In another embodiment, the invention relates to a development method in which the above under 1.

gO and 2. problems described do not occur, when using toner particles with a mean particle size of up to 20 µm and also up to 10 µm and in which the problem described under 3 is avoided even if the middle Particle size of the carrier particles up to 50 μm and in particular

AFTER Ιί

• · · m

-7-

special up to 30 μπι amounts. This procedure aims to a clear, sharp image of high quality can be produced in which fine lines or points or density gradations can be reproduced with high fidelity.

In a method of developing a latent image on an image carrier by supplying a two-component developer of magnetic carrier particles and toner particles onto the surface of a developer transfer carrier for the purpose of forming a developer layer on the latter, the developer layer on the Transfer carriers introduced into an oscillating electric field and in this way the latent image the image carrier is developed, the specified task of the invention can be solved with magnetic carrier particles that have a spherical shape (are sphered).

In a modification of this method, spherical or spherical toner particles can be used as the toner particles be used.

In a further embodiment, the invention relates to a development method in which magnetic carrier particles of magnetic particles and thermoplastic synthetic resin particles can be used and the development in one oscillating electric field is carried out.

The invention also aims to provide a development method for an electrostatic latent image and a magnetic latent image with which a simple Fixation of the toner particles on the recording or copier paper is possible, a ta

~ ■ ■ ^ ™ ν m ^ y [- ^^ ^^ ^ v w ^ v ^ · ^^ * v »^^ μ w * ^ v ^ j ^^ ^^ ^ v ν ν ^^ m i ^ * ^ r ψ

35 on of toner particles

Carrier particles

prevents toner and carrier from being used in fine powder form and fine lines and dots as well Density gradations are reproducible with high fidelity.

The invention therefore also relates to a method for developing an image produced on an image carrier Image (latent image) by forming a layer of a two-component developer from toner particles and magnetic carrier particles on the surface of a developer-transfer carrier and developing the image on the image carrier by means of this developer layer, the specialty of which is that as toner particles those used for pressure fixation and development in an oscillating electric field is carried out.

Another object of the invention is to provide a method for developing an electrostatic image or charge image to work with fine toner and carrier particles of a two-component developer capable, in which the occurrence of fogging and the accumulation of the carrier particles on the surface of the Image carrier can be avoided and which ensures the development of a sharp image of high quality.

The invention thus furthermore relates to a method for developing a latent image on a Image carrier by forming a developer layer from toner particles and magnetic carrier particles on the surface of a developer transfer medium and developing the latent image on the Image carrier by means of the developer layer produced in this way, the developer layer on the transfer carrier is kept out of contact with the image carrier, a

-9-

Control electrode in the gap or space between We introduced these carriers in order to prevent the accumulation of To control toner particles from the developer layer on the image carrier, an alternating voltage component to either the control electrode or the transmission carrier applied and the development is carried out within the resulting oscillating electric field.

The following are preferred embodiments of the Invention explained in more detail with reference to the drawing. Show it:

Figures 1, 2, 3, 16, 17 and 18 are schematic representations of developing devices for carrying out the developing method according to the invention and

Figures 4 through 15 are graphical representations of the devices results obtained according to the above figures.

Fig. 1 schematically illustrates a developing device for carrying out an embodiment of the method according to the invention.

By a charging and exposure device, not shown becomes an electrostatic latent image on the outer surface of a drum-shaped image carrier 1 generated from a photosensitive element such as Se, exists. The image carrier 1 rotates in the direction of the arrow according to FIG. One near the picture carrier arranged developer transfer carrier 2 consists of a sleeve (cylinder) 2a made of a non-magnetic Material, such as Al, and a magnet roller 2b, which are provided with a number of magnetic poles in their circumferential direction

• ^: "" · "■■" 3 ^: A11655

is. The magnetic poles of the magnet roller 2b are generally set to a magnetic flux density of 500-1500 Gauss magnetized. To transfer a developer D from buckets of developer containers 6 to a development unit A wil-d held the sleeve 2a stationary, while the Magnetic roller 2b set in rotation w: approx. Optionally can dip magnetic roller 2b stand still while the sleeve 2a rotates. Furthermore, both Turn the magnetic roller as well as the sleeve. When the sleeve 2a rotates, however, is the direction of transmission of the developer D is the same as the rotating direction of the sleeve 2a, while with the magnet roller 2b rotating, the Direction of conveyance is opposite to the direction of rotation. According to Fig. 1, the magnet roller 2b rotate clockwise and the sleeve 2b counterclockwise so that the developer D in the direction opposite to that Is transported clockwise.

In the arrangement according to FIG. 2, the magnet roller 2b is arranged in a rotationally fixed manner, while the sleeve 2a is opposite rotates clockwise. In this case, the magnetic flux density is that opposite to the image carrier 1 Magnetic pole larger than that of the other magnetic poles. To further increase the magnetic flux density of the dem Image carrier 1 opposite magnetic pole can, according to FIG. 3, two poles of the same or different polarity be arranged close together.

The height of the layer of the developer D transported on the peripheral surface of the sleeve 2a becomes limited by a scraper blade 4. When the developer D enters the development unit or zone A, a part of the developer is attracted to or attached to the image carrier 1 while the rest of the developer on the outer surface of the sleeve

-11-

2a further transported in the direction of the arrow 'and finally by a cleaning blade 5 from J the circumferential surface of the Sleeve 2a is stripped off. A stirring screw 7 is used to circulate or loosen the developer D within of the container 6 and to uniformize the quantitative ratio between toner and carrier particles.

When carrying out the development, large quantities will be used the toner particles contained in developer D are consumed.

A toner hopper 8 is provided for replenishing the toner particles T, with a feed roller 9 having recesses is set in rotation in its outer surface in such a way that it conveys toner particles T into the developer container 6, to replenish the used toner particles. The on-order further comprises a current source 10, the tw— <-g about a protection-

ii resistor 11 applies a bias to the sleeve 2a. '& This current source 10 serves as at least one an oscillating electric field-generating generator in order to enable the developer D e development A between the sleeve 2a and image carrier 1 in oscillation.

The essential feature of the described development - (( 25 method is that the magnetic carrier particles used have an average particle size of 5 - 50 μπι and the toner particles one of up to 20 um.

In the previous magnetic brush development process, the developer D is electrically charged by means of friction and applied to the charged part by the Coulomb force of the image carrier 1 attracted. As a result, there is an unavoidable limit to the downsizing of the Particle size of the developer for its sufficient

-12 charge for developing.

This problem occurs with the method according to the invention does not appear even if the developer consists of fine particles.

Since according to the invention an oscillating electric field is applied, the particles of the developer D vibrate between the sleeve 2a and the image carrier 1, so that on the latter, a visible image can be developed by the developer D even if the developer D does not come into such intimate contact with the image carrier 1 as in the previous magnetic brush development process is required.

15th

To avoid fogging (image fogging), the thickness of the developer layer is preferably smaller than the distance between the image carrier and the sleeve. The developer can be in the same direction or opposite to the Move the image carrier, and its speed of movement is preferably greater than that of the image carrier, although this is not a particularly critical feature.

In the method according to the invention, fine Carrier and toner particles are used which are unsuitable for the previous magnetic brush development process are.

If the particle size of the carrier particles used in the process of the present invention is below 5 µm, the magnetization becomes too weak; on the other hand when the particle size exceeds 50 micrometers, the image quality can not be "improve, and it can easily occur (electrical shear) and discharge aperture, so that a *), in particular below 4 μΐη

-13-

high voltage cannot be applied. ffcfH-e toner particles a particle size of less than 1 µm, in particular can ^ Te "also under the influence of vibration do not simply separate from the relevant carrier; at

a particle size of over 20 µm decreases the image resolution away. In view of this, the toner particle size is preferably 0.5-20 µm, and more preferably not 1 - 20 um elected. The mean amount of charge on the toner in this case is preferably more than 1 µC / g and preferably 3 - 300 µC / g, in particular 10 - 100 µC / g \ (This The mean amount of charge is determined using the blow-off method.)

Since a DC voltage is applied to prevent fogging and a vibrating electric field to vibrate the developer D is generated between the image carrier 1 and the sleeve 2a, the determination of the distance between these particles is problematic. If the space is too narrow, a discharge occurs between the image carrier and the sleeve, thereby damaging the image carrier and preventing the developer D passing therebetween from being transferred or conveyed. On the other hand, if the distance is large, the effect of the counterelectrode decreases, so that a recording (copy) sufficient development density cannot be obtained and the fan effect is increased. Satisfactory results can be obtained if the distance between the image carrier and the sleeve is up to 2000 µm, in particular from a few 10 \ up to 1000 µm.

A direct voltage of 50 - 500 V is applied as a bias voltage to prevent fogging to maintain a higher potential than in the non-image area. To get the developer D in oscillation

·· ". 341655

move, an alternating current of 100 cHz to 10 kHz, preferably 1-5 kHz, is used. the DC voltage can be smaller than specified V'ert if the toner has magnetism. if an inversion development is carried out, a higher DC voltage can of course can be applied. D: .e AC voltage depends on the frequency. The higher the voltage, the more so The vibration of developer D is stronger or more violent, but there is a probability for that The more likely it is for obscuration and discharge to occur. If the frequency is even higher, the developer cannot accept the change, so density and The sharpness of the developed image and thus the image quality.

Apart from their mean particle size, conventional magnetic carrier particles can be used as carrier particles can be used in the method according to the invention.

Examples of the carrier particles are ferromagnetic or magnetic particles made of iron, chromium, nickel, Cobalt and its compounds or alloys, e.g. Fe-O., Ύ-iron oxide, chromium dioxide,

Manganese oxide, ferrite, manganese-copper alloys, etc., as well as insulating particles made by coating the surfaces of particles from the specified substances modified with synthetic resins such as styrene type, vinyl type, ethyl type, rosin modified Resins, acrylic type resins, polyamide resins, epoxy resins, polyester resins and the like, or with a fatty acid wax, such as palmitic acid, stearic acid and the like were obtained. Insulating magnetic ones are preferred Particles with a specific resistance of min-

8 1 "ί

Λ least 10 cm, preferably of at least 10 cm _Xl-r and in particular of at least 10 Λ-cm. If the

-15- M

specific resistance is too low, AnIe-; '■)

Application of the bias to the developer-transfer carrier ^: *

ger injects the charge into the carrier particles, so that vi, these can adhere to the surface of the image carrier, ·· ■; in this case, therefore, a sufficiently large bias voltage cannot be applied. "|

The specific resistance is determined as follows: Ά

After the particles in a vessel with a cross-sectional. | j

2 '■' -

area of 0.50 cm and compacted by tapping have been, the so condensed partial

Chen with a load of 1 kg / cm applied. '$

A voltage that has an electric field of 1000 V / cm \\

generated between the charge and a bottom electrode, I:

is applied and the current measured is shown as ) \

read the specific resistance. The isolating '(

Particles do not necessarily have to be of the type * \

in which a coating layer made of a synthetic resin or the like. jij

is applied to the surface of magnetic particles, ή

but can also be of the type where magneti-!

see particles dispersed in a synthetic resin. ή

The carrier particles described are on the same
Manufactured in the same way as the conventional carrier particles;
for use in the method according to the invention
they in a manner known per se according to their mean
Particle size classified. ~

The conventional non-magnetic or magnetic
Toner particles can in the process according to the invention

can also be used after their mean particle size has been appropriately adjusted by means of classifying devices known in the art. Preferably
magnetic toner particles of the type are used
in which the toner particles are fine magnetic particles

■ ■ ■ - ..—! - ■■ • «« · · · 1 thereby the • | i. . . 3411655 ... . 30% by weight · .: ,: .. .. · .. '· to party -16- the 1 contain. Preferably is lot magnetic particles up to . if

■ H ■ toner particles contain magnetic particles

A they by the magnetic force of the developer transfer

f
?; i 5 affected by the carrier 2 arranged magnets, so that the

I property that creates an even pile

I Magnetic brush further improved and an image

1 haze is prevented and scattering or

Indeed, flying of the toner particles can hardly occur. | .j 10 When the amount of I magnetic substance gets too big, however, the

.. · ''. Magnetic force between this substance and the carrier particles is too great to achieve a sufficient development density. In addition, the fine magnetic particles 15 appear at the surface of the toner particles on call% and thereby produce the problem that the control of

1 the frictional charging is difficult and the toner particles are damaged or become between the carrier ^; particles can clump together.

20th

The toner particles of the type described can be produced by known production processes, for which purpose the resin or synthetic resin and fine magnetic particles, as described in connection with the carrier particles, • 25 is used and coloring or dye components, such as ■ carbon or soot, and a charge control agent, so-

i remotely required to be added.

j The developer to be used according to the invention is through

i 30 Mixing of the carrier and toner particles mentioned in the * same quantity ratio as the previous two-component

• 3 developers prepared. Additionally required

i | if necessary a fluidizing agent to improve the

4 flowability and sliding properties of the particles

$ 35 Cleaning agent for the surface of the image carrier, etc.

mixed in. Examples of fluidizing agents are colloidal silica, silicone varnish, metal soap ,; nonionic surfactants, etc. Examples for the cleaning agent sinä surfactants or surface-active Agents such as metal salts of fatty acids, silicone substituted with organic groups, fluorine and the same.

Using developer D and the described Development conditions, development is then carried out in the following two cases. In the first case there is the developer D deposited on the charged area of the image carrier exclusively from the toner particles; in the second part, both toner and carrier particles are turned on to form a visible image the image carrier 1 attached. In both cases, the desired result can be achieved if the conditions are appropriately chosen be achieved.

1. To carry out the development with exclusively Toner particles, the carrier particles must remain on the outer surface of the developer-transfer carrier 2 and only the toner particles are allowed to oscillate or vibrate between image carrier 1 and transfer carrier 2. In order to the toner particles the forces of attraction., like the Coulomb force with the carrier particles and the van der Waals force, overcome and separate from the carrier particles can separate are a strong oscillating electric field and a high amount of charge on the toner particles in connection with a high restraint force of the magnet roller 2b required to represent an oscillation To prevent carrier particles. In order to prevent the carrier particles from vibrating together with the toner particles, if the particle size of the carrier particles is preferably larger than that of the toner particles, that is

-18-

The magnetic restriction force acting on the carrier particles is greater than the electrostatic force which these particles transfer to the image carrier, and the amount of charge on the toner particles is greater than 1-3 μθ / g (preferably 3-300 ° C / g) . A large amount of charge is necessary especially when the particle size is small.

The method for generating the visible image on the image carrier 1 exclusively by means of the toner particles offers the advantage that the surface of the image carrier 1 is not damaged by the carrier particles and the visible image can be generated twice on the image carrier 1, on which "already a visible Image has been generated.

2. When a visible image is formed on the image carrier 1 by means of both the toners and the carrier particles it is not necessary for the toner particles to overcome the force of attraction with the carrier particles and part with them. It is for this reason that the requirements to be met by the toner and carrier particles are not so strict. As the carrier particles through an oscillating electric field between the image carrier and transmission carrier 2 is set in vibration;:! their particle size may be smaller than that of the toner particles; consequently, the can affect the toner particles acting magnetic restriction or restraint force be weak, and the amount of charge of the toner particles can be small. In this case you can Carrier and toner particles are used which have smaller particle sizes than those described under 1 Own case used particles. When developing

-19-

treatment with only the toner particles can be a visible
High quality image cannot be easily obtained if the
The particle size of the carrier particles is less than 10 µm and that of the toner particles is less than 5 µm. When developing with both the toner and carrier particles, the mean particle size of the carrier particles is about 5 µm and the toner particles about
1 to produce a high quality image. Since the toner
particles can be made to vibrate, you too
Sticking together or clumping are prevented.

An effective measure also consists in:
to allow a magnetic field to act on the oscillating zone of the developer and to change this magnetic field either time-dependently or spatially. ? |

The following are the results from among the above
described development conditions carried out
Try explained. >, - i

1

Attempt A w

i '{

Spherical ferrite particles;. ·.

a mean particle size of 20 µm, a Magne-!; ' tization of 50 emu / g and a resistivity of 10 Α-cm used; than $ toner particles have not been report--magnetic particles are used, consisting of * 100 parts by weight of a commercially available styrene-acrylic i? resin, 10 parts by weight of carbon black and 5 parts by weight (of the dye) nigrosine and had an average particle size of 10 µm. ., Using the f 'device of Figure 1 was carried out the development under jj the conditions that the quantity ratio of toner particles to the carrier particles ν in which the developer | ⁶ developer located container D 10 wt .-% loading \\ wore. · 'Ί;

-20-

The image carrier 1 consisted of a photosensitive Cd £ element, which at a peripheral speed of 180 mm / s circulated. The highest potential of the charge image produced on the image carrier 1 was -500 V. Der The diameter of the sleeve 2a was 30 mm and its speed of rotation was 100 rpm. The magnet roller 2b had a magnetic flux density the N and S poles of 500 Gauss at a speed of 1000 rpm. The thickness of the developer layer on the development unit or zone was 0.2 mm; the distance between the sleeve 2a and the image carrier 1 was 0.3 mm or 300 μπι set. The bias voltage to be applied to the sleeve 2a contained a direct voltage component of -250 V and an AC component of 1.5 kHz, 400 ".

After the development, the image was transferred onto plain paper and passed through the sample sheet by a heat roller fixing device with a surface temperature fixed at 140 ° C. The image formed on the recording or copying paper was clear or clear. sharp, had an extremely high density and showed neither edge effect nor fogging. Even after the When producing 50,000 copies, the copy images remained flawless until the end. For comparison purposes a reproduction was made under the same conditions, as described above, but carried out with the difference that on the sleeve 2a only one the existing bias voltage has been applied to the DC voltage component. In this case, the copy image was blurred low density obtained. An experiment was also carried out under the same conditions with the difference carried out that the distance between sleeve 2a and image carrier 1 to 3.0 mm (3000 μπι) and the thickness of the The developer layer on the development unit was changed to 0.7 mm. The copies received in this case

2411655

-21 images showed kinten effect and low density.

Attempt B

B As the carrier particles, insulating spherical ferrite particles having an average particle size of 15 µm, one Magnetization of 70 emu / g and a resistivity of at least 10 ji-cm with a synthetic resin coated, used. Non-magnetic particles having an average particle size were used as the toner particles of 5 µm. The development was carried out by means of the apparatus shown in FIG. 2 under the condition that at the developer D in the developer container 6 is the ratio of toner particles to carrier particles Was 5% by weight.

In this case, the same conditions as in the case of Experiment A were maintained on the image carrier 1. The sleeve (cylinder) 2a, which had a diameter of 30 mm, was driven at a speed of 150 rpm. The magnetic flux density. of the magnetic pole facing the developing unit or zone A of the Magnet roller 2b was 1200 gauss. The developer layer in the development area was 0.3 mm thick. The distance between the sleeve 2a and the image carrier 1 was 0.4 mm (400 µm). The bias applied to the sleeve 2a existed from a direct voltage component of -100 V and an alternating voltage component of 3 kHz, 1200 V.

After the development under the above conditions, the image was transferred to plain paper and passed through a heat roller fixing device having a surface temperature of 140 ⁰ C. The image obtained was extremely clear, had a high density, and showed no edge or fogging. Even after

ι -22-

the production of 50,000 copies proved the image quality to the end as consistently flawless.

A duplication process was carried out under the same conditions, with the difference that the de ^:! The bias voltage applied to the sleeve 2a consisted exclusively of the direct voltage component. The copied images thus obtained were found to be unsatisfactory in terms of density and clarity or sharpness.

10

Furthermore, in the manner described, but with the difference that the distance between the sleeve 2a and image carrier 1 to 3.0 mm (3000 μπι) and the thickness of the The developer layer on the development unit was changed to 0.7 mm, additional copies were made. In the Copy images obtained in this case showed an edge effect at a low density.

Attempt C

Carrier particles dispersed in resin, prepared by dispersing 50% by weight of fine ferrite particles in a resin, with an average particle size of 10 µm, a magnetization of 3O emu / g and a specific resistance of at least

1 4
at least 10 Λ-cm were used as carrier particles.

Magnetic particles made from 100 parts by weight of a commercially available styrene-acrylic resin, 10 parts by weight of carbon black, 5 parts by weight of nigrosine and 5 parts by weight of fine particles of ferrite (mean particle size 3 µm) were made used as toner particles. The development was carried out by means of the device according to FIG. 1 under the condition that in the case of the developer D in the container 6, the ratio of the toner particles to the carrier particles Was 10% by weight.

-23-

In this case, the image carrier 1 consisted of a j

CdS photosensitive member, and its peripheral speed was 180 mm / s. The highest potential of the charge image generated on the image carrier 1 was ″ _;

-500 V. The sleeve 2a, which had an outside diameter of 30 mm, was driven at 100 rpm. The magnetic flux density of the N and S poles of the magnet roller 2b rotating at 1000 rpm was 500 gauss. The developer layer on the development unit was 0.2 mm thick. [

The distance between the sleeve 2a and the image carrier * ■ was 0.3 mm (300 μm). The bias voltage impressed on the sleeve 2a consisted of a direct voltage component ο "· ■ of -2 50 V and an alternating voltage component of 1.5 kHz, 400 V. '

After i'l under the specified conditions durchgeführ- | j th development, the (toner) image on plain paper was ■■ '. transferred, and the sheet of paper (with the toner image); j

was passed through a heat roller fixing device having a surface temperature of 140 ⁰ C. The copy image obtained was extraordinarily clear or sharp and had a high density without any edge effect or distortion

veil. Even after making 50,000 copies>

the results remained practically unchanged. ■

25th

On the other hand, a copy was made with the ^

Modification that the bias voltage V; consisted only of the direct voltage component. ti

The copied images obtained were blurred and had a low density. The attempt was also made among the II specified conditions, but with the; · ί

Difference, that the distance between sleeve 2a and · «

Image carrier 1 to 3.0 mm and the thickness of the developer- $

layer on the developing unit changed to 0.7 mm ⁽ⁱ _;

became. In this case, the copied images obtained showed ύ

"· 34116 ί

-24-those who had low density had an edge effect.

Attempt D

The carrier particles consisted of insulating spherical ferrite particles with an average particle size of 4 μm, a magnetization of 70 emu / g and a specific resistance of 10 ¹⁴ A-cm. The toner particles used were non-magnetic particles with an average particle size of 5 μm. The development was carried out by means of the apparatus according to Pig. 3 * v / ob with developer D in container 6 a ratio of toner particles to carrier particles of 5% by weight was maintained.

In this case, the same image carrier 1 as' in ~ Ver. . ".'-. such A is used. The sleeve 2a, which had an outside diameter of 30 mm, was driven at 150 rpm. The magnetic flux density of the pole of the magnet roller 2b opposite to the developing area A was 1200 gauss, while the density between the poles was 800 gauss. The developer layer in the development area was 0.3 mm thick, the distance between the sleeve 2a and the image carrier 1 was 0.4 mm. The to the Bias voltage applied to sleeve 2a consisted of a DC voltage component of -100 V and an AC voltage component of 3 kHz, 1200 V.

After development the .angegebenen conditions, the image was transferred to plain paper, and then for fixing by a heat roller fixing device having a surface temperature of 140 - passed ⁰ C. The image obtained on the copier paper was extremely clear or sharp and had a high density without edge effects or fogging. Even after 50,000 copies had been made, the results remained unchanged.

-25-

If only the DC voltage component is applied to the sleeve 2a as a preload was created, showed the received

^δ ten copy images have a slightly lower density |

and clarity than in the above case.

For comparison purposes, the distance between the sleeve 2a and the image carrier 1 was set to 3.0 mm and the thickness of the developer layer changed to 0.7 mm on the developing unit. The copy images obtained in this case showed edge effect at low density.

In addition, no oscillation of the carrier particles could be observed in experiments A and B. It can therefore, it is believed that the carrier particles will be practical under the conditions used in these experiments not swing.

Figs. 4 and 5 are graphs showing the relationship between the frequency and the Magnitude of the alternating voltage for generating the oscillating electric field under the conditions that are used in Tests A and B gave satisfactory results. The cross-hatched sections indicate indicate the area in which image fogging was observed, while the longitudinally hatched sections indicate the area in which a dielectric breakdown or breakdown occurred. The diagonally hatched Sections represent the area in which the image quality deteriorated; the unshaded sections show the area in which a high quality visible image can be achieved. The dotted Sections represent a low frequency range in which an uneven development can be observed

"···· ■" · ■■■ · ■■ * · "* 3 ^:

-26-was.

Figs. 6 and 7 each illustrate the relationship : wipe the voltage and del: frequency of the alternating current to generate the oscillating electric l'eldi under the conditions used in the experiments C and D gave satisfactory results. As can be seen from these graphs, are the results according to experiments C and D are analogous to those of experiments A and B.

In Experiments C and D, it was found that the vibration of the carrier particles occurred in the upper portion within the useful range indicated by the dashed lines, but not in the lower portion of this useful range. Within the useful or effective range, copy images excellent in density, tone gradation and resolution were obtained in the portion above the broken lines. The waveform of the alternating voltage component used according to the invention need not only correspond to a sine wave, but can also be a square, sawtooth or triangular wave. As long as the toner of the two-component developer is magnetic, can be under the specified developer ^; conditions also convert magnetic latent images into visible images.

In the previous magnetic brush development process, on the other hand, recorded or copied images can be made high quality cannot be achieved because of the particle size of the toner and carrier particles when using a two-component developer cannot be reduced.

In the method according to the invention for developing a

-27-! 1

electrostatic or charge image are toner particles U

a mean particle size of 1-20 µm and carrier-I

particles with a mean particle size of 5 - 50 µm ύη · - j |

ter effect of a vibration (oscillation) on this jö

Particles are used, in which case there is an on- · ^

drawing of satisfactory image density, tone gradation |.

and can achieve resolution. §

Since the developer consists of two (or more) components bell 0, the charge of the toner can be better stabilized

while the toner clumping does not occur so easily as with the one-component developer. i

According to another embodiment of the invention -; 5

spherical magnetic particles are called magnetic ii

Carrier particles of the two-component developer used | and the development in the oscillating electric field i

executed. In this case, magnetic 1

Carrier particles as well as toner particles in the form of a fine one
Use powder without difficulty. The one at this:
Embodiment used carrier of the developer
preferably corresponds to the following - ■ expedient conditions.

If the magnetic carrier particles are spherical or ..:

are spherical, the circulating or stirring!

ability of toner and carrier as well as transferability of the developer, so that a clumping (aggregation) of the toner particles with each other and

prevents the toner particles with the carrier particles

can be. If, however, the magnetic carrier; particles have a large mean particle size,
I have the following problems:

1. Since the pile (ear) on the developer transfer

Magnetic brush generated by the carrier is coarse, can there are non-uniformities in the toner image even if the charge image is developed while the Particles are set into oscillation by the electric field,

2. As the density of the toner in pile decreases, one can Cannot achieve high density development (of the copy image).

The former problem can be eliminated by reducing the mean particle size of the carrier particles. As tests have shown, this effect occurs from an average particle size of less than 50 μm. In particular, with an average particle size of less than 30 μm , it is found that the first-mentioned problem practically no longer occurs. The second problem can also be solved by reducing the mean particle size of the magnetic carrier. In this case, the density of the toner in the pile is high and the development can be realized with a high density. However, if the carrier particles are too fine, there are problems that

3. the carrier particles can attach to the surface of the image carrier together with the toner particles and that

4. The toner particles tend to scatter or fly around.

These phenomena are related to the intensity of the magnetic field acting on the carrier particles as well as the intensity of the magnetization of the carrier particles due to the magnetic field. Generally start

3Ά11Β55

-29-

however, these phenomena gradually occur, though the mean particle size of the carrier particles below 15 µm is, while they are particularly noticeable at an average particle size of less than 5 µm.

Part of the accumulated on the surface of the picture carrier Carrier particles are transferred to the copy paper together with the toner, while the rest is transferred together with the toner through a doctor blade, a felbrush or the like. is stripped from the image carrier. The previous carrier particles that only consisted of a magnetic Substance exist, but pose the following problems:

5. The carrier particles transferred to the copy paper are not fixed on the copy paper, so that they can easily part with it.

6. When the carrier particles remained on the surface of the image carrier by means of the cleaning device removed, they can be removed from the surface of the photosensitive element Slightly damage the image carrier.

The problems mentioned under 5. and 6. can be solved in that the magnetic carrier particles Material such as a synthetic resin is incorporated which can be fixed on the recording or copying paper. This is because the magnetic carrier particles are coated with a substance that can be fixed on the copy paper or the carrier is made of a material in which the magnetic powder is dispersed and that on which Copy paper can be fixed, or if a thermoplastic resin is used for the magnetic carrier particles is used, the information on the copy paper can be

-30-

Adhering carrier particles also fix (on the copy paper) by the action of heat or pressure, and they do not cause any damage to the surface of the image carrier if they are removed from it using the cleaning device: - turn away. If these carrier particles have an average particle size of 5-15 μη », the problem mentioned under 3 practically does not occur, even if the carrier particles are on the surface of the image carrier and transferred to the copy paper. If, however, there is a build-up of beams (problem 3) should occur, a recovery mechanism can expediently be provided.

From the above considerations it follows that the particle size of the spherical magnetic carrier below

50 µm and preferably in the range of 30-5 µm should. Preferably, the spherical magnetic carrier particles also contain a substance that can act can be fixed to the recording or copying paper. 20th

Conventional magnetic carrier particles can be used for this purpose.

Examples of suitable carrier particles are spherical particles made from the substances previously mentioned on page 14 and spherical particles whose surfaces are coated with synthetic resins, etc. mentioned on the same page are, as well as particles that are in per se known classifying devices with respect to their mean Particle size have been classified, or synthetic resin particles dispersed therein or from a fatty acid wax spherically enclosed fine particles.

When carrier particles with a synthetic resin or the like, spherical or sphered, result

I ♦ · ·

In addition to the effect already described, the additional., j

chen effects that on the developer transfer carrier | . ger a uniform developer layer is formed and

a high bias is applied to the transmission carrier. t

can be. In this case, the ';',

achieve the following effects: p '

: J Vl

1. The carrier particles are generally easy to collect magnetize and attract in the direction of the main axis, |

but with a spherical shape they lose their Directivity As a result, an equal

Form moderate developer layer, and the Auftre-; ι an area of locally low resistance

as well as non-uniformity of the developer layer - b

thickness can be prevented. (I.

2. If the resistance of the carrier particles is higher, the | Avoid the edge effect occurring in the carrier particles, and there is no concentration of the electrical

look at the field at the edge or edge section, so;

that even if a high prestress is applied to thin,: Developer carrier neither the latent Charge image disruptive discharge to the surface of the image carrier nor a breakthrough or breakdown of the

Bias occurs. .- ^;

This possibility of applying a high prestress l.,

means that the specified effects are fully achieved

let len if the development according to the invention under _; :

the oscillating electric field when a j

oscillating preload is carried out. Although for '■'"

the spherical carrier particles a wax of the specified!

Kind can be used in terms of I.

Durability of the carrier a synthetic resin previously loaded |

type preferred. For example, ■ .;}

spherical magnetic carrier particles are used, be:

which the ratio of major axis to minor axis below at least 3 and which have no sharp edges. The magnetic carrier particles preferably have a specific resistance of at least K) £ l-cm

13 '

and preferably at least 10/1 cm.

The magnetic carrier particles of the specified type can be produced as follows: If the carrier particles spherical magnetic particles of increased resistance or carrier particles coated with synthetic resin, If possible, spherical or round magnetic particles are selected, which are then coated with a synthetic resin will. When the carrier particles are dispersion-type magnetic fine particles, as possible highly magnetic fine particles are selected, which then after the formation of particles dispersed in synthetic resin a rounding treatment (sphering treatment) according to a spray drying process for the recovery of in Resin dispersed particles are subjected.

Try

Spherical ferrite particles coated with synthetic resin and having an average particle size of 30 µm, "a magnetization of 50 emu / g and a specific resistance

1 4
of at least 10 η-cm were used as the support.

After a grinding granulation process, the toner consisted of

• \ move out preserved, non-magnetic particles

30 100 parts by weight of a commercially available styrene-acrylic resin, ν 10 parts by weight of carbon black and 5 parts by weight of nigrosine (middle

§ particle size 10 µm). The development took place in the middle, ls

the device according to FIG. 1, wherein in the developer D in the developer container 6, the ratio of toner particles

'] 35 to carrier particles was 10% by weight. The mean charge

-33- j

amount of the toner was 15 μϋ / g. ι

The one consisting of a light-sensitive CdS element Image carrier 1 rotated at a peripheral speed of 180 mm / s. The highest potential of the image carrier 1 generated charge image was -500 V. The rapid outer diameter of 30 mm possessing sleeve 2a was driven at 100 rpm. The magnetic flux density of the N-Ind S-PoIe of the magnetic roller 2b (speed 1000 / min) was 900 gauss. The thickness of the developer layer in the development zone A was 0.6 mm, the distance between Sleeve 2a and image carrier 1 0.5 mm. The bias voltage applied to the sleeve 2a consisted of a direct voltage component of -250 V and an alternating voltage component of 1.5 kHz, 500 V. According to FIG. 1, the developer layer reached the surface of the image carrier 1 in touch.

After the image development under the specified conditions the image was obtained by means of a corona discharge transfer device onto plain paper and then by passing the copy paper through a heat roller fixing device a surface temperature of 140 C. The one ultimately obtained on the copy paper The copy image had a high density, which was extremely clear or sharp and showed neither edge effect nor Obfuscation. Even after 50,000 copies were made, the image properties remained practically unchanged.

If on the other hand, however, were used as carrier particles milled ferrite particles having virtually the same properties as the carrier particles described above with a resin coating and an average particle size of 30 \ in which the voltage value which can be applied AC voltage component was at most about

I »· t

• t Il

JAI1655

-34-

2/3 of the specified tension and the copy image obtained showed coarseness.

Try F

Rounding treatment made by dispersing 50% by weight of fine ferrite particles in a synthetic resin magnetic particles subjected to heating having an average particle size of 20 µm, one Magnetization of 30 emu / g and a specific resistance of at least 10 η-cm were used as carrier particles used. The toner particles consisted of non-magnetic particles of an average particle size of 5 µm. The development was carried out by means of the device according to FIG. 3, with developer D in the container 6, the ratio of toner particles to carrier particles was set to 5% by weight. The middle The amount of charge of the toner was 30 μθ / g.

In this experiment, the same image carrier was used as in experiment E. It had an outside diameter of 30 mm Owning sleeve 2a was driven at a speed of 150 / min. The magnetic flux density of the development zone A opposite pole of the magnet roller 2b was 1200 gauss. The developer layer was 0.5 mm thick, and the distance between the sleeve 2a and the image carrier 1 was 0.7 mm. The to the sleeve 2a The bias voltage to be applied consisted of a direct voltage component of -200 V and an alternating voltage component of 2 kHz, 1000 V. This experiment succeeded the developer layer on the sleeve 2a is not in contact with the surface of the image carrier 1.

After the development was carried out under the specified conditions, the developed image was passed through

• * * * · I · • · · t ■ · 1655 f ■ '3 "Λ1 I.

Transfer corona discharge to plain paper and then f '

for fixing by a heat roller fixing device |;

a surface temperature of 140 ° C passed through. %

The copy image obtained had a high density and was above

extremely clear (i.e. sharp or fine-grained) and without Kan- s4

effect and obfuscation. Even after making f *

50,000 copies, the image quality deteriorated practically [j

table not. U

If, on the other hand, such particles are used as carrier particles

det were those of the described rounding treatment ν;

(sphering treatment) not subjected by heating H

had been, the voltage value of the applicable j

Change of voltage component (only) about 2/3 of the indicated

given voltage, resulting in a coarse-grained copy image;

was holding. i;

Attempt G

Magnetic particles were used as carrier particles,
prepared by dispersing 50% by weight of ferrite fine particles in a synthetic resin, and a
mean particle size of 20 \ im, one magnetization
of 30 emu / g and a specific resistance of

possessed at least 10 x ^ -cm. In addition, these particles were subjected to the rounding treatment by heating. The toner particles became non-magnetic
Particles with an average particle size of 5 µm are used. The development was carried out by means of a practical

the device according to FIG. 1 corresponding device
under the conditions that the ratio of the toner particles to the carrier particles in the developer D in the container 6 was 5% by weight and the developer layer was also
the surface of the image carrier 1 is not in contact

reached. The mean charge amount of the toner was
30 /

10

15th

20th

-36-

The image carrier 1 used was that according to Experiment E. The one with an outside diameter of 30 mm Sleeve 2a was driven at a speed of 100 rpm. The magnetic flux density of the N- and S-Po. ". E was 700 Gauss, the speed of the magnetic roller was 500 / min. The developer layer was 0.7 mm thick. Lie on the sleeve 2a applied or to be applied bias voltage consisted of a direct voltage component of -20C V and a AC voltage component of 2 kHJ 1000 V.

After development under the specified conditions, the developed (toner) image was transferred to normal paper by corona discharge and then passed through a heating roller fixing device with a surface temperature ^{of 140 ° C. for fixing.} The image obtained had a high density and was extremely clear (fine-grained or sharp) and did not show any edging or fogging. In addition, it was superior to the image obtained in Experiment F because it had higher resolution and density. Even after 50,000 copies had been made, there was practically no deterioration in the image quality.

When using the rounding treatment by heating, non-subjected particles as the carrier particles the voltage value of the alternating voltage component that can be applied was at most 2/3 of the specified voltage, where a grainy image was obtained.

If, in experiments E, F and G, the frequency and voltage of the alternating voltage component applied to the sleeve 2a were changed, the results shown in Figs. 8 and 8 respectively were obtained.

Figs. 8 and 9 each show the relationship between

-37-

the voltage and the frequency of the alternating current for generating the oscillating electric field under the Conditions that were satisfactory in experiments E, F or G. Delivered results. As can be seen from these graphs, the results are the Experiments E, F and G are analogous to those of experiments A and B.

In Fig. 8 (Experiment E) and Fig. 9 (Experiment F and G), the areas above the dashed line indicate the dielectric Strike-through areas for the case of non-spherical carrier particles.

The described embodiment of the invention ensures advantageously that a clear, fine-grained reproduction picture without any obscuration by means of a carrier having an average particle size of 30 µm or below and a toner having an average particle size of up to 10 µm can be produced.

In the development method according to another embodiment According to the invention, development is carried out using a spherical toner of the two-component developer under the oscillating electric field, so that fine toner particles and fine magnetic table carrier particles can be used without any difficulty. For the in this embodiment When the developer used is used, a toner of the type specified below is preferably used.

The toner particles together with the magnetic carrier particles first form the developer layer the developer transfer medium. Then the toner particles are through the between transfer carrier and Image carrier generated electric field separated from the developer layer and attracted to the electro-

♦ t

-38-

static or magnetic latent image attached to the image carrier. Then the obtained toner image becomes transferred to the copy paper either directly or via an intermediate transfer element and fixed on this. The toner must therefore form the developer layer in cooperation with the carrier particles form with an appropriate density and separate from the carrier particles of the developer layer and selectively attach to the respective latent image. In addition, it must have such properties that it can be easily transferred from the image carrier.

In order to meet these requirements, spherical toner particles are used in the present invention. Such Toner particles have better flowability and improve charging due to friction with the carrier particles and consequently form a developer layer more expediently in cooperation with the carrier particles Density. During development, spherical toner particles can be separated evenly from the developer layer, selectively to the charge image or the like. attached and also easily transferred from the surface of the image carrier will. It is believed that when spherical toner particles are used, the interfaces between them and the carrier particles and between them and the surface of the image carrier are reduced so that the uneven force, which cannot be easily controlled, such as the van der Waals force, to a minimum can be reduced. In addition, the spherical shape (spherical shape) causes in contrast to such with needle-like projections, edges or the like. or a thin elongated shape no charge concentration and neutralization of the discharge. The toner particles are therefore made spherical or spherical in such a way that that the ratio of major axis to minor

ί. ι

axis is at least below 3. t

The spherical toner particles can be produced by various methods indicated below. ... The starting material «: consist of resins or synthetic resins,. '·;■', e.g. a resin dt; s styrene or vinyl type, a
rosin-modified karz, a resin of acrylic. ' ^! or a polyamide type, an epoxy resin, a polyester resin
or the like, a coloring component or a dye,
such as carbon black, and a charge control agent that may be added. If the toner is magnetic type, ψ

it also contains fine particles of ferromagnetic t

h or magnetic substances, for example made of a metal, ii

for example, iron, chromium, nickel, cobalt or the like., the encryption <

bonds and alloys, e.g. Fe-O ₄ , f-

α-iron oxide, chromium dioxide, manganese oxide, ferrite, manganese oil

Copper alloy or the like. The toner is made from these components

raw materials, for example after spray drying j

process in which these substances come together '

melted and kneaded and then in a 1 solvents are dissolved, the resulting solution from

squeezed out of a nozzle in hot air and thereby the solution;

means of the ejected droplets for extraction /

spherical particles is evaporated. In a flow-:

A flow coater is the solidified or dried particles of the melted oil ground and kneaded mixture, and the resulting 'ground particles are through a nozzle in hot air I blown out to thereby remove the synthetic resin component of the part j

to melt the surface and give the latter a spherical i

To give shape. In a granulation polymerisation;

tion process is the synthetic resin in a solution of an i

Prepolymer from which the dye or the like. is \ separately polymerized and precipitated ,. Instead of

of the flow coating process mentioned, the

Another method is used to stir toner particles into hot water to soften the synthetic resin content and to make it spherical in shape, and then filtered and dried. Farther the toner particles can also be formed as microcapsules; the manufacturing and treatment processes described are also applicable to such toner particles.

In general, as the average particle size of the toner particles becomes smaller, the amount of charge qualitatively decreases Ratio to the square of the particle size, while the gravitational force, which is not easily controllable, e.g. the van der Waal's force, on the other hand, increases. In this case, therefore, the toner particles are difficult to remove from the Carrier particles separate, and as soon as the toner particles adhere to the non-image areas of the surface of the Adhere to the image carrier, they cannot easily be stripped off by the friction of the conventional magnetic brush so that image fogging occurs. This problem occurs in the usual magnetic brush development process particularly clearly evident when the mean particle size of the toner particles is below 10 μm lies. This problem is addressed by use of the present invention spherical toner particles and by carrying out development by means of the developer layer in one vibrating electric field solved. This means that the toner particles under the action of the vibrating electric field easily from the developer layer onto the image areas and non-image areas of the surface of the image carrier and can also be easily separated from these areas. If the The developer layer is brought into frictional contact with the surface of the image carrier toner particles adhering to the non-image areas without

-41-

further removed or slightly in the loading image areas be convicted.

When the thickness of the developer layer is less than the distance between the surface of the image carrier and the developer-transfer carrier, become toner particles with a small amount of L idung hardly attached to the image areas and non-image areas and hardly brought into frictional contact with the surface of the image carrier. In this case, they are stored the toner particles do not adhere to the image carrier under frictional charging, and toner particles may occur a mean particle size of up to 1 μm down were used. As a result, a latent Charge image with high fidelity and good repeatability for a clear, fine-grained toner image to be developed. Since the oscillating electric field continues the bond between the toner and Carrier particles weakens, the adhesion of the carrier particles to the toner particles can be reduced. In particular when - as mentioned - the thickness of the developer layer is smaller than the distance between The image carrier surface and the transfer carrier vibrate the toner particles having a large amount of charge in the oscillating electric field at the image areas and non-image areas; Depending on the intensity of the electric field, the carrier particles also vibrate, and as a result, the toner becomes selective to the charged image areas transferred to the image carrier surface, while the attachment of the carrier to this surface can be significantly reduced.

On the other hand, if the mean particle size of the toner is large, the graininess decreases as mentioned (coarseness) of the copy image increases significantly. In general

Ii (M

-42-

when using a fine toner having an average particle size of about 20 μΐη a development with a Achieve a reproduction resolution of 10 lines / mm will. On the other hand, when using a fine toner with a mean particle size of less than 10 μm improve the resolution still quite considerably, so that a high quality copy image is obtained in which the Density gradations with high): reproduced fidelity. For the reasons mentioned, the middle Particle size of the toner below 20 μm and preferably below 10 μm. So that the toner particles to the electrical Able to follow the field, their amount of charge should preferably be greater than 1-3 µC / g. A bigger one Charge amount is required especially when the particle size is small. One that meets these requirements Toner can be produced by the methods described; if necessary, the toner can also be in on known classifying devices are classified according to average particle size.

The toners to be used are preferably composed of magnetic toner particles which are fine magnetic particles contain. The proportion of the fine magnetic particles is preferably up to 60% by weight, and particularly up to at 30% by weight. The toner particles containing magnetic particles are transferred by the magnetic force of the carrier affects existing magnets, so that the uniform design of the magnetic brush is further improved image fogging is prevented

3Q and scattering of toner particles hardly occurs. However, if the amount of the magnetic substance is too large, that between the toner and carrier particles will become Acting magnetic force is too great to achieve a sufficient development density. Also be the fine magnetic particles to the surface of the

·· <·· <ι ι ■ at SJ ₁

Toner particles are attracted, so that din control of the travel |

exercise charging becomes difficult and the toner particles? |

break and clump between the carrier particles [|

nen. ■ .; ''?

yi

Attempt H |

Non-magnetic particles of H

100 parts by weight of a commercially available styrene-acrylic ^ '

resin, 10 parts by weight of carbon black and 5 parts by weight of nigrosine; used, which after grinding and granulating according to ahm

The flow coating process mentioned above were spherically shaped ]} (sphered) and a mean particle size of

10 um owned. The support consisted with resin ba- y

layered spherical ferrite particles of a middle |

Particle size of 30 µm, a magnetization of &

14 t

50 emu / g and a specific resistance of 10 η-cm. \\

The development took place by means of the device according to:

Fig. 1 with a toner / carrier ratio of the '

Winder container 6 located developer D of

10% by weight. The mean charge amount of the toner was
15 µC / g.

The one consisting of a light-sensitive CdS element
Image carrier 1 ran at a peripheral speed of
180 mm / s around. The highest potential of the electrostatic or charge image generated on the image carrier 1
was -500 V. The sleeve (cylinder) 2a, which had an outside diameter of 30 mm, rotated at a speed of 100 rpm. The magnetic flux density of the N and S poles
the magnetic roller 2b (speed 1000 / min) was 900 Gauss.
The developer layer was 0.6 mm thick, and the gap
between sleeve 2a and image carrier 1 was 0.5 mm. the
Bias applied to the sleeve 2a consisted of one
DC voltage component of -250 V and an alternating

-44-

Voltage component of 1.5 kHz, 500 V. The development took place while the developer layer was in contact with the image carrier 1.

After developing under the specified conditions, the developed (toner) image was made by means of a Corona discharge device transferred to plain paper and fixed by a heat roller fixing device directed. The image formed on the copy paper was extremely clear or fine-grained at high density without edge effect and obfuscation. After 50,000 copies, there was practically no image deterioration .

On the other hand, when a toner which did not undergo the hot air rounding treatment in the flow coater was used was subjected, the copy image obtained in this case was in terms of fogging and fine grain are inferior to the image generated in the manner described above, when the remaining conditions were the same as described above.

Attempt I.

The toner consisted of non-magnetic particles to an average particle size of 5, spherically shaped by the flow coating method. As the carrier, magnetic particles made by dispersing 50% by weight of fine ferrite particles in a synthetic resin and having an average particle size of 20 µm, a magnetization of 30 emu / g and a specific resistance of at least 10 η-cm, which were subjected to the rounding treatment, were used was. The development took place by means of the device according to FIG. 3

-45-

with a toner / carrier ratio in developer D of 5% by weight. The mean charge amount of the toner was 30 μθ / g.

The image carrier 1 was the same as in experiment H. The sleeve 2a, which had an outside diameter of 30 mm, was, however, driven at a speed of 150 rpm. The magnetic flux density of the magnetic pole facing the development zone A was 1200 Gauss, and the thickness of the developer layer was 0.6 mm. _{A distance of 17.7} mm was maintained between the sleeve 2a and the image carrier 1. The bias voltage impressed on sleeve 2a consisted of a direct voltage component of -200 V and an alternating voltage component of 2 kHz, 1000 V. In this exemplary embodiment or experiment, the thickness of the developer layer on sleeve 2a was smaller than the distance between sleeve 2a and image carrier 1.

After developing under the specified conditions, the developed image was transferred onto plain paper and then passed through a heat roller fixing device having a surface temperature of 140 ° C for fixing. That produced on the recording or copying paper The image had a high density and was extremely clear or sharp with no edge effects or fogging. This image quality practically did not deteriorate even after 50,000 copies were made.

On the other hand, when a toner which was not subjected to the above-mentioned rounding treatment was used, the image obtained showed inferior fogging and clarity or fine-grain properties even if the other conditions mentioned above were met.
35

• ·

-4 δ- Try J

The development was carried out using a developer D of the type described in connection with experiment I and practically corresponding by means of a device those according to Fic. 1, where the toner particle / carrier particle ratio of the developer D in the container 6 was set to 5% by weight. The mean amount of charge of the The toner was 30 µC / g.

The same image carrier 1 was used as in experiment H. The sleeve 2a with an outer diameter of 30 mm rotated at a speed of 100 / min. The magnetic flux density of the N and S poles was 700 gauss (Magnetic roller speed 500 / min). The developer layer was 0.6 mm thick. The distance between sleeve 2a and Image carrier 1 was 0.7 mm. The bias voltage applied to the sleeve 2a consisted of a direct voltage component of -200 V and an alternating voltage component of 2 kHz, 1000 V.

After the development, under the specified conditions, the developed image was transferred to plain paper by corona discharge and then through AIIF dine heat roller fixing device passed an Oberflächentemperiitür of 140 ⁰ C for fixing. An extremely clear or fine-grained image free of edge effects or fogging was obtained on the copy paper. This image had a higher resolution and density than the image produced in Experiment I. Image deterioration practically did not occur even after 50,000 copies.

One by means of a toner which is the rounding treatment was not subjected, on the other hand, the image formed was as in the case of the comparative experiment

SUBSCRIBE] ■:

Experiment I, regarding obfuscation and fine-grainedness \

the IdId | generated in the manner described above

inferior.

For a change in frequency and voltage of the ^ n the j

Sleeve 2a applied alternating stress component in the j

Experiments H, I and J see the results in Fig. 10 I.

(Experiment H) and FIG. 11 (Experiment I and J).

As can be clearly seen from the experiments described above, the inventive development

, \ procedure in which the development by means of the two

Component developer carried out with spherical toner particles in an oscillating electric field becomes a recorded or copied image without any obfuscation and with excellent fineness, which cannot be achieved with previous methods leaves.

According to a further embodiment of the invention, the magnetic carrier particles consist of the two-component developer for example, magnetic particles and a synthetic resin such as one in a synthetic resin dispersed magnetic powder or synthetic resin-coated magnetic particles; besides, these are Particles preferably spherical. The magnetic carrier particles have an average particle size of preferably up to 50 μm and in particular from 30-5 μm.

The preferred toner used here is composed of the synthetic resin and further the fine particles of the magnetic Substance as it has been described for the wearer, and it may also contain one Dye such as 9 carbon black and a charge control agent. The toner that is known after a

-48-

th process can be produced, has an average particle size of up to 20 μm and preferably up to 10 μπι.

Attempt K

The carrier particles consisted of spherical carrier particles coated with synthetic resin, which were produced as follows: Ferrite particles with an average particle size of 25 μm are suspended in hot air, and the styrene-acrylic resin also used for the toner particles is dissolved in a solvent. The solution is sprayed onto the toner particles by means of a nozzle, which are then dried and then have an average particle size of 30 μm, a magnetization of 50 emu / g and a specific resistance of at least 10 ¹⁴ n-cm. Non-magnetic particles, produced by grinding and granulating a mixture of 100 parts by weight of a commercially available styrene-acrylic resin, 10 parts by weight of carbon black and 5 parts by weight of nigrosine, with an average particle size of 10 μm, are subjected to the rounding treatment (treatment to achieve a spherical shape) by means of hot air. The non-magnetic particles thus prepared are used as toner particles. The development takes place in the device according to FIG. 1 with a toner particle / carrier particle ratio of the developer D in the container 6 of 10% by weight. The mean amount of charge on the toner particles is 15 μθ / g.

The image carrier 1 was again photosensitive CdS element and ran at a peripheral speed of 180 mm / s. The highest potential of the charge image generated on the image carrier 1 was -500 V.

The speed of rotation of the one with an outside diameter of 30 mm Sleeve 2a was 100 rpm. The magnetic flux density of the N and S poles of the magnet roller was 90 gauss, the Speed of the magnetic roller 1000 / min. With a thickness of the developer layer in the development zone A of 0.6 mm the distance between the sleeve 2a and the image carrier 1 was 0.5 mm. The bias to be applied to the sleeve 2a consisted of a direct voltage component of -250 V and an alternating voltage component of 1.5 kHz, 500 V.

After development was carried out under the specified conditions, the developed (toner) image was made using transferred to plain paper by a corona discharge device and then fixed by a heat roller fixing device a surface temperature of 140 C. The image formed on the copy paper possessed again high density with extremely high sharpness or fine grain, without edge effect or obscuration to show. Even after 50,000 copies were made, the image quality remained practically unchanged.

Attempt L

The styrene-acrylic resin also used in experiment K, in in which 50% by weight of fine ferrite particles having an average particle size of 0.2 µm were dispersed, was ground and then subjected to a hot air treatment to obtain spherical particles having an average particle size of 20 µm, a magnetization of 30 emu / g and one

gQ to obtain a specific resistance of at least 10 O-cm. These particles were used as carrier particles. As the toner particles, the flow coating method obtained spherical non-magnetic particles of the same composition as the corresponding ones

3g particles according to experiment K used. The development

I ·

-50-

followed by means of the device according to FIG. 3, where there! Ratio of toner particles in developer D contained in container 6 to carrier particles 5% by weight fraud. The mean amount of charge on the toner was 20 µC / g.

The same image carrier 1 as in experiment K was used. The one with an outside diameter of 30 mm However, the sleeve (cylinder) 2a was driven at a speed of 150 rpm. The magnetic flux density of the development zone A opposing magnetic pole of the magnet roller 2b was 1200 gauss. With a thickness of A developer layer of 0.6 mm was the distance between the sleeve 2a and the image carrier 1 0.7 now. The bias voltage on the sleeve 2a had a direct voltage component of -200 V and an alternating voltage component of 2 kHz, 1000 V.

After developing under the specified conditions, the developed image was transferred to plain paper by corona discharge and then passed through a heat roller fixing device having a surface temperature of 140 ^° C. for fixing. The image obtained on the copy paper had a high density, was extremely clear or fine-grained and free from edge effects and fogging.

Even after 50,000 copies produced, the ^one image quality did not change practically.

Try M

Development was carried out using Developer D, its carrier and toner particles being the same as those at Developer D corresponded to Experiment L, and practically corresponded by means of a developing device that of FIG. 1, wherein the toner / carrier particle

Ratio of developer D in developer tank 6

Was 5% by weight. The average amount of charge on this toner

contributed 30

In this experiment, the same image carrier 1 as in
Trial K used. The one outside diameter of

30 mm sleeve 2a rotated with a rotating A

number of 100 / min. In the case of a magnetic flux dielectric, the N and fi

S-PoIe of 700 Gauss was the speed (the magnet | f

roll) 500 / min. The developer layer was 0.6 mm thick. (j

The distance between the sleeve 2a and the image carrier 1 ■]

was C-7 mm. The protrusion lying on the sleeve 2a

voltage consisted of a DC voltage component ^

of -200 V and an AC component of Q

2 kHz, 1000 V. - 1

After development under the specified conditions p]

the developed image was corona discharged onto f

Plain paper transferred and then passed through a heat roller- '. \

Fixing device with a surface temperature of 1

140 ° C out. The one on the duplication or >

Copy paper formed image had a high density and _,; : was extremely clear or sharp or fine-grained

and free from edge effects and obscuration. This'>

Image was in terms of resolution and density according to; ·:

such L obtained picture superior. Even after 50,000 her- · ;; made copies changed the quality of the image practically ", '

not. To change the frequency and voltage of the;

AC voltage component applied to sleeve 2a:

in the above experiments, the results are in Fig. 12K

provided for experimental and K in Fig. 13 for experimental L and M DAR h.

As can be seen from the experiments described above, in the method according to the invention in advantageous

3 4 · Ί Ί ο b b

-52-

adherently a carrier having an average particle size below 30 µm and a toner having an average particle size of less than 10 µm can be used, with an excellent, clear or fine-grain reproduced image without fogging can be obtained without being practical Problems arise.

In yet another embodiment of the invention the development is carried out using a two-component developer composed of toner particles for pressure fixing and carrier particles under an oscillating electric field in order to avoid the difficulties that said toner particles adhere to the carrier particles and possibly clump together.

In this embodiment, the particle size of the toner and carrier particles can be further reduced, to simplify the fixing of the toner image on the copy paper and to improve the quality of the reproduced image.

In this embodiment of the invention, known pressure fixing toner particles which can be fixed on the copying paper with a line pressure of about 20 kg / cm by means of a suitable pressure roller are used as the toner particles of the two-component developer. Such toner particles can be produced from the specified starting materials by various processes known per se. A dye (tinting component), '■' · * ° gnMonefnff. ^ M _- carbon black, and optionally a · charge control agent are viscous resins or synthetic resins, for example a polyolefin, an ethylene-vinyl acetate copolymer, a polyurethane, a rubber or the like . or an aliphatic wax such as palmitic acid, stearic acid or the like. mixed in. If you want the toner to be magnetic, be

^ 1655

-53-

fine ferromagnetic or magnetic particles of metals such as iron, chromium, nickel, cobalt and the like, or their compounds or alloys such as Fe ₃ O ₄ , γ-iron oxide, chromium dioxide, manganese oxide, ferrite, manganese-copper alloy or the like. Like., dispersed in synthetic resin. Microcapsule-shaped toner particles known per se are obtained by coating the outside of these particles with a synthetic resin of high chargeability (optionally with the dye or the like), as is generally used for toner particles for heat setting. The spherical, " see dispersed toner particles" are preferred

</ « Touts & hibotf (h .i,

-n used, which by rounding (sphering) of the particles described by the spray drying process, the flow coating process, the granulation polymerization process or the like. were manufactured. The flow coating process to achieve rounded or spherical particles can be carried out using either hot water or hot air. <M ^ Vtstosti & i € &»> / k * fi * A»

When the above-described spherical toner particles are used, their flowability is improved, see above that it is avoided that the toner particles adhere firmly to the carrier particles or clump together. aside from that the charging of the toner particles by friction with the carrier particles is also improved, so that only the toner particles in an appropriate density from the developer layer formed together with the carrier particles to the electrostatic latent images are deposited and thus the transmission power from the surface of the image carrier on the recording or copying paper and the fixability can be improved.

Since the development according to the invention in an oscillating

• ^: '34Ί 1655

electric field occurs, can result from the use of pressure fixing toner particles of the Z ^ eikomponentenentwickler and problems resulting from the reduction in the particle size of the toner particles are avoided will. In other words: the toner particles bound in the developer layer can get under easily separate from the developer layer by the vibration of the electric field applied to them and attach to the image areas on the surface of the image carrier. When the image carrier surface is in Frictionized contact with the developer layer can occur in the non-image areas Toner particles adhering to this surface are easily removed from that surface or to the charge image areas be convicted. When the thickness of the developer layer is less than the distance between the surface of the image carrier and the developer-transfer carrier, There may be migration of the small amount of charge toner particles to the image areas and non-image areas can be suppressed considerably. Since the toner particles do not come into frictional contact with the image carrier surface, they adhere does not apply it to the image carrier due to frictional charging, so toner particles about 1 µm in size are used can be. In this way, a sharp or fine-grained toner image can be achieved, which reproduces the latent charge image with high fidelity and good repeatability.

Since the oscillating electric field continues to weaken the bond between the toner and carrier particles, the adhesion between the carrier and toner particles is reduced. The influence of the vibrating The electric field increases when spherical toner particles are used. Especially if the

The thickness of the developer layer is less than ~ the distance O

between the surface of the image carrier and the ent-?, ·

winder transfer carrier, vibrate the toner particles, which have a large amount of liquid, under the Schwin · - "■ ·.

g. »nd the electric field in the image areas and non-image areas Areas, and the carrier particles oscillate depending on the intensity of the electric field also, so that the toner is selective to the charge;

image area shifted on the surface of the image carrier. This prevents the accumulation of carrier particles on the

The area of the image carrier is noticeably reduced. :

Try N ?.

Non-magnetic particles made from 100 parts by weight of a K.

Ethylene-vinyl acetate copolymer, 10 parts by weight $

Carbon black and 5 parts by weight nigrosine, after grinding and 3

Granulating according to the flow coating process spherical .1

Risch formed and an average particle size of 10 to possessing were used as toner particles. The carrier particles used were spherical ferrite particles with an average particle size of 30 μm, a magnetization of 50 emu / g and a specific resistance

1 4
stand of about 10 η-cm, coated with a styrene-acrylic resin. The development took place by means of the device according to FIG. 1 with a toner / carrier ratio of the developer D in the container 6 of 10% by weight * ■

The mean amount of charge on the toner was 15 µC / g.

The image carrier 1 had a photosensitive CdS element

on ran at a peripheral speed of 180 mm / s;

around. The highest potential of the -h on the image carrier 1

generated charge image was -500 V. The one external |, i

diameter of 30 mm own sleeve 2a turned!,

with 100 / min. The magnetic flux density of the N and S poles of the h

'·' ■ -56-

; - 1 magnetic roller 2b (speed 1C00 / min) was 900 Gauss * at In a developer layer 0.6 mm thick, the

I stood between the sleeve 2a and the image carrier 10.6 mm.

ι The pre-applied or to be applied to the sleeve 2a

5 voltage had a DC component of -250 V and an AC voltage component of 1.5 kHz, 500 V.

A After development under the specified conditions

£ was the developed (toner) image by means of a corona

';] 10 discharge device transferred to plain paper and "

U then used for fixing by a pressure fixing device

tl leads, the one with a line pressure or linear

λ pressure of 20 kg / cm working calender or pressure roller

exhibited. The toner image created on the copy paper

15 showed a high degree of fixation and a high density, and

it was extremely clear or sharp or fine-grained

I and free from edge effects and obscuration. This he-

; ■ The result changed even after 50,000 copies were made

ij not.
; | 20th

': Attempt 0

ij As the toner particles, they became non-magnetic

'Particles as in experiment N, but with a medium one

25 particle size of 5 µm was used. The carrier particles consisted of spherically shaped ferrite particles prepared by dispersing 50% by weight of fine ferrite particles having an average particle size of 0.2 µm in the same synthetic resin as that used for the toner, then kneading and grinding the mixture and

subsequent rounding treatment (to form spherical particles) using hot air; the particles produced had a mean particle size of 20 µm, a magnetization of 30 emu / g and 35 has a resistivity of at least 10 Ω-cm ..

-57-

The development took place by means of a device according to FIG. 3 with a 5% by weight toner content of the developer D in the container 6. The average charge amount of the toner was 30 \ iC / g.
B.

The image carrier 1 was the same as in experiment N. The 30 mm thick sleeve 2a rotated at 150 rpm. the Magnetic flux density of the magnetic pole of the magnet or magnet roller facing the development zone A 2b was 1200 gauss. In the case of a developer layer 0.6 mm thick, the distance between the sleeve was 2a and image carrier 1 0.7 mm. The one lying on the sleeve 2a Bias voltage consisted of a direct voltage component of -200 V and an alternating voltage component of 2.kHz, 1000 V.

The developed image was again corona discharged onto plain paper and then under the same Conditions fixed as in experiment N. The image produced had the same properties as those in the experiment N are described. The image quality did not deteriorate even after 50,000 copies were made.

Try P

Development was carried out with the same toner and carrier as in Experiment 0 and by means of a developing device according to FIG. 1 (with the exception of a different distance between image carrier 1 and developer-transfer carrier); the toner / carrier ratio of the developer D in the container 6 was 5% by weight. The mean amount of charge of the toner was 30 µC / g.

The image carrier 1 was the same as in experiment N. The sleeve 2a rotated with an outer diameter of 30 mm

with 100 / nin. The magnetic flux density of the N and S poles was 700 Gauss at a speed of 500 rpm. The thickness of the developer layer was 0.6 mm, the distance between the sleeve 2a and the image carrier 1 was 0.7 now. The bias voltage on the sleeve 2a had a direct voltage component of -200 V and an alternating voltage component of 2 kHz, 1000 V.

After development under the specified conditions the developed image was transferred to plain paper by corona discharge and then placed under the conditions in Experiment N conditions described. The fixed image had the same advantageous properties as that image obtained in experiment N. It was superior to the image produced in Experiment 0 in terms of resolution and density. After 50,000 copies were made, the image quality remained practically unchanged until the last copy obtain.

To change the frequency and voltage of the alternating voltage component applied to the sleeve 2a the results are shown in FIG. 14 for experiment N and in FIG.

Due to the development with application of the oscillating electric field to the developer layer from the Two-component developer in the development zone can be used as the toner a pressure fixing toner, so that the fixation of the toner image on the copying paper can be carried out more easily than with previous methods leaves. In addition, in this way a reproduced or copied image can be produced without any obfuscation, but with excellent clarity or fine grain can be guaranteed.

-59- If

FIGS. 16 through 18 illustrate other embodiments shaping of development devices for implementation |

of the method according to the invention. | j

These embodiments each comprise a drum-type 'ξ-shaped image carrier 1 with an electrophotographic, p,

photosensitive layer or dielectric layer, '■■

on which an electrostatic latent image or latent ■

Charge image by means of a corresponding device
with conventional charging and exposure unit, ti

Multi-needle electrode or ion control electrode (not ^

shown), one made of aluminum 'j \

or the like. manufactured sleeve (cylinder) 2a and a magnet ^

roll 2b or 2c, which is arranged in the sleeve 2a and U

around its circumference a number of magnetic poles N and 'f.

S has. ί |

The sleeve 2a and the magnet roller 2b or 2c form one
Developer and carrier are relative to each other
rotatable. 16, the magnet roller 2b rotates

clockwise and the sleeve 2a counterclockwise. The magnetic poles N, S of the magnetic roller 2b are general '; mine to a magnetic flux density of 500-1500 Gauss
magnetized.

A so-called magnetic brush is formed in that
a layer of a on the outer surface of the sleeve 2a
Developer 2b made of toner particles and carrier particles is deposited due to the magnetic flux. The magnetic brush moves

the rotation of the sleeve 2a and the magnet roller 2b
with the sleeve 2a and is inserted into a developing area 2a. ·;

One of a magnetic or non-magnetic
Element existing regulating or scraper blade 4 is used

34T1655

-60-

¹ to adjust the height and thus the amount of the magnetic brush on the outer surface of the sleeve 2a. A cleaning blade 5 serves to wipe the magnetic brush from the sleeve 2a after it has passed through the development area.

⁵ rich A. In a developing tank 6, a stirring screw 7 is arranged for equalizing the quantitative ratio of toner particles to carrier particles by circulating the developer D. A toner funnel 8 is used to refill toner particles T. The toner particles T ¹ ^ are introduced into the developer container 6 by a feed roller 9 with recesses formed in their outer surface. The latter is therefore with § a two-component developer consisting of toner and carrier

I filled with particles.

»% Ι κ

I The developing device described corresponds to

S plus their structure in the essentials of the previous one

i: | Developing device for two-component developers.

f | In the device of Fig. 16, the N and

I 20 S-PoIe of the magnetic roller 2b each same magnetic flux

^: dense, and the magnetic roller 2b runs in the opposite direction to the ¹

; Sleeve 2a around. The device according to FIG. 17 differs

; det is different from that of Fig. 16 in that sicli

j; the magnetic roller does not turn. The device

y 25 measure Fig. 18 have the individual N and S poles;

\ i Magnet roller 2c does not have the same magnetic flux density. In particular ^

\ Sondere the device differs by Fig.itj

_; . from that according to FIG. 17 in that the magnet

; flux density of the magnet opposite to the image carrier 1

30 poles different from that of the other magnetic poles

'is and that (in contrast to the image carrier) two N-PoIe, which generate a repulsive magnetic field between them, are arranged next to one another.

35 To further increase the magnetic flux density of the dem

34Ί 1655

-61-

1 opposite magnetic pole, an N- and a fine S-PoI can be arranged close to each other, instead of arranging two magnetic poles of the same polarity close to one another at this point, as in FIG. 18. With such an arrangement a stable, i.e. safe development can be guaranteed.

In the embodiments described above, the distance between the sleeve 2a and the blade 5 for adjusting the thickness of the developer layer and the. The distance between the sleeve 2a and the image carrier 1 is set so that the magnetic brush formed on the sleeve 2a does not come into contact with the surface of the image carrier 1. A control electrode 12, which in turn does not hinder the transfer of the toner particles from the magnetic brush to the image carrier 1, for example a wire stretched parallel to the axial direction of the sleeve 2a, is arranged in such a way that a voltage having an alternating voltage component is applied either to it Control electrode 12 or the sleeve 2a can be placed in order to generate an oscillating electrical F * Id in the area ά * --- development zone A. Development takes place in the manner shown in FIG. 6 under this oscillating electric field. A current source 13 for applying ';' the tension on the sleeve 2a and a protective resistor t * - »d 14 is provided.

The control electrode 12 extends preferably through the space between the magnetic brush and the image carrier 1, so that the distance between the sleeve 2a and the control electrode 12 is at least a multiple of 10 µm (dozer, of mlcrczr.s ) is. The distance between control electrode 12 ursi image carrier 1 is of the same order of magnitude, while Oer distance between the sleeve 2a and image carrier 1 to an i-OOO .mu.m. If the distance between HUl ** -

ι -62-

2a and control electrode 12 is too small, it is difficult to Form an even pile (ear) of the magnetic brush, and the toner particles can not be sufficient Manner to be supplied to the developing unit, so that the development is not stable or steady can be done safely. If the distance between the control electrode 12 and the image carrier 1 is too small, a Discharge occur. If, on the other hand, the distance between the sleeve 2a and the image carrier 1 is greater than: .000 µm (2 m), the electrode effect of the sleeve 2a decreases, so that a sufficiently large development density cannot be obtained and the edge effect becomes more apparent. The control electrode 12 consists in particular of 100 1000 around thick wires, the iin called interspace are stretched parallel to each other at intervals of 0.5 - 5 mm. Optionally, a grid with a mesh size 0.5 - 5 mm can be used. Such a control electrode 12 offers the advantageous effects that they are transferred to the electrostatic charge image on the image carrier 1 by the magnetic brush Toner particles exerts a sufficiently large control effect, hardly hindered the flight of the toner particles and about toner particles adhering to it can be separated from it.

The development in the oscillating electric field takes place through the application of an alternating voltage component ^! ; e containing voltage to the control electrode 12 arranged in the manner described or the sleeve 2a in the manner explained below.

1. The voltage with an alternating voltage component becomes impressed only on the control electrode 12. A DC voltage of up to 600 V is preferred superimposed alternating voltage of 200 - 4000 V.

-63- O

Frequency from 100 Hz to 10 kHz, preferably from '

1-5 kHz or more, together with the DC voltage f \

of up to 600 V impressed on the sleeve 2a. To the %

prevention of fogging by the toner is r. -l

this DC voltage preferably to a higher %

Potential than the potential in image-free loading |

range of the image carrier 1 set. |

2. The one containing an alternating voltage component

Voltage is both at control electrode 12 and ■

applied to sleeve 2a. If both change ^:

Voltage components have the same frequency,

is generally preferred to the sleeve 2a a ■ · ^v \

higher AC voltage applied than to the control. |

electrode 12. When using different '·. "· ■ _ ■ .; · |

Frequencies is preferably the one frequency around p

some orders of magnitude different from the other * $

Frequency to prevent beating in the electrical ί-

see box to prevent. The higher frequency r-

own AC voltage component is preferred ^

towards the sleeve 2a, because in this case ■: ': ■.

a uniform cloud of toner particles between) ;;

the sleeve 2a and the control electrode 12 can occur ^c . The alternating voltage to be applied to the sleeve 2a

voltage component is preferably greater than that on!

the control electrode 12. Furthermore, i

a superimposed direct voltage of up to 600 V to -

the sleeve 2a and the control electrode 12 are applied. %

The DC voltage to be applied to the sleeve 2a should. ft

be greater than the potential of the .image-free " ^: ?!

Area of the image carrier 1 to a concealment 'j, -.: Ü

by preventing the toner .. In
the magnitudes of frequency and voltage of the alternating. Stress component also preferably in the range described under 1. above. '"' ■

-64-

3. The voltage having an alternating voltage component is only impressed on the sleeve 2a. In this case an alternating voltage of 200-4000 V at a frequency of 100 Hz to 10 kHz, preferably of 1-5 kHz, applied to the sleeve 2a. This alternating voltage is preferred with a direct voltage of up to 600 V superimposed. A direct voltage of up to 600 V to the control electrode is also advantageous 12 created. In this case, too, the DC voltage at the sleeve 2a is at a higher potential than that of the non-image area on the image carrier 1 is set to be obscured by to prevent the toner.

In addition to a sinusoidal waveform, the alternating voltage component can also have a square or triangular waveform. Although there is a certain dependence on the frequency, the higher the voltage, the more violently the magnetic brush of the developer vibrates, so that the separation and throwing off of the toner particles from the carrier particles takes place more easily. On the other hand, dielectric breakdown ujn (■ V-sl-Acc- / tends to occur. Fogging (of the toner image) can be prevented by the AC voltage component. Dielectric breakdown or breakdown can also be achieved by completely or partially isolating the surfaces of the control electrode 12 and the sleeve 2a by means of a synthetic resin or oxide coating or by using insulating carrier particles, as will be described in more detail below.

In the development method according to this embodiment the magnetic brush from the two-component developer is kept out of contact with the image carrier 1,

on

and the control electrode 12 is arranged therebetween so that the development by means of the magnetic brush under the oscillating electric field takes place. This causes separation and throwing off (transfer) of the toner particles Improved by the magnetic brush, an accumulation of carrier particles on the image carrier 1 is prevented and thus the use of toner and carrier particles in fine powdery form enables, remnachzu can be produce a high quality toner image in this way.

Since here the magnetic brush pile is not with the picture carrier is in contact, the control electrode is arranged in between and the development in the oscillating If there is an electric field, these can be reduced by a two-component developer made up of fine toner and carrier particles Make full use of the advantages offered to produce a sharp or fine-grained image of high quality.

Try Q

Resin-coated spherical ferrite particles having a mean particle size of 30, a magnetization of 50 emu / g and a specific resistance of at least 10 ¹⁴ n-cm were used as the carrier.

The toner consisted of non-magnetic particles of 100 parts by weight of a commercially available styrene-acrylic resin, 10 parts by weight of commercially available carbon black and 5 parts by weight of Nigrosine, and it had an average particle size of 10 µm and was prepared by grinding and granulating. The device was used for development 16 with a ratio of toner particles of the developer D in the developer container 6 to the carrier particles of 10% by weight. The mean amount of charge on the toner was 15 µC / g.

The image carrier 1 used had a photosensitive one Element made of CdS on; its peripheral speed was 180 mm / s. The highest potential of the 1 generated electrostatic or charge image was -500 V, the potential of the image-free areas -100 V.

The sleeve 2a, which has an outer diameter of 30 mm turned at 100 / min. The magnetic flux density of the N and The S-PoIe of the magnet roller 2b was 900 Gauss at a speed of 1000 rpm. With a 0.4 mm thick developer layer the distance between the sleeve 2a and the image carrier 1 was 1.5 mm (i.e. 1500 μm). The control electrode 12 was 0.5 mm far from the surface of the image carrier 1. A superposition voltage was applied to the control electrode 12 applied from a direct voltage of -200 V and an alternating voltage of 1.5 kHz and 1000 V, while a DC voltage of -250 V was applied to the sleeve 2a. To form the control electrode 12 were 0.2 mm diameter wires spaced 1 mm apart parallel to the sleeve 2a excited.

After development under the specified conditions, the developed (toner) image was transferred to normal paper by means of a corona discharge device and then passed through a heating roller fixing device with a surface temperature of 140 ^° C. for fixing. The image produced on the duplicating or copying paper had a high density and was extremely clear or sharp.

3Q effect and concealment. Even after 50,000 manufactured Copies, the image quality was practically unchanged.

Attempt R
As carrier particles, by dispersing 50% by weight

'' · '""''"'" ** ' ^{% e} 34i 1655 I.

magm'ti- | ί made of fine ferrite in a cow resin see particles with a mean particle size of 20 | Jm, || a magnetization of 30 emu / g and a specific |

Resistance of at least 10 η-cm used; die4e Particles were subjected to rounding treatment (to form spherical dips) by heating. the Toner particles consisted of non-magnetic particles an average particle size of 5 µm. The development took place in the device according to FIG. 17 with a Toner particles / carrier particle ratio of 5% by weight im Developer D in developer container 6. The average amount of charge of the toner was 30 µC / g.

The same image carrier 1 as in experiment Q was used. The sleeve 2a again had an outer diameter of 30 mm, but its speed of rotation was 150 rpm. The magnetic flux density of the magnetic pole of the magnet roller 2b facing the development zone A was 1200 gauss. With a developer layer thickness of 0.5 mm, the distance between the sleeve 2a and the image carrier 1 was 1.0 mm. The control electrode 12 consisted of einem.Maschengefüge, wherein 50 to thick wires obliquely to the axial direction of the sleeve 2a and each of 1 mm to form wide openings were arranged crossing. This control electrode 12 was arranged at a distance of 0.3 mm from the surface of the image carrier 1. A bias voltage consisting of an alternating voltage component of 300 Hz and 700 V was applied to the control electrode 12, while a bias voltage with a direct voltage component of -200 V was impressed on the sleeve 2a.

After developing under the specified conditions, the developed image became that described in Experiment Q. Way transferred to the paper and fixed. The image thus produced had the same properties as

they are given in experiment Q. After 50,000 copies there was also virtually no deterioration in image quality.

Try S

Development, transfer and fixation were carried out in the same way as in experiment Q, only with the difference that that a wire spacing of 2 has now been chosen for the control electrode, the alternating voltage component of the the superimposition voltage applied to the control electrode 12 was 300 kHz at 500 V and an alternating voltage of 2 kHz and 1000 V in addition to the direct voltage was applied to the sleeve 2a. The one obtained in this way The image on the copy paper had the same properties as in Experiment Q and remained even after production of 50,000 copies practically unchanged.

Tries

Development, transfer and fixation took place again in the same way as in experiment R, the only difference being that the wires of the control electrode 12 overlap while establishing 2 mm wide meshes and crossed the sleeve 2a in addition to the direct voltage component an alternating voltage component of 2 kH and 400 V was applied. The image quality corresponded to that according to Experiment R and remained practically unchanged even after 50,000 copies had been made.

30th

Try u

Development, transfer and fixation were carried out in the manner described in Experiment S, only with the difference that on the control electrode

3-1655

a DC voltage of> -150 V was and the sleeve 2a a Superimposed voltage from a direct voltage component of -250 V and an alternating voltage component of 1.5 kHz and 2000 V was impressed. The image formed under these conditions had the same properties as in experiments Q and S.

Experiment V

Under otherwise the same conditions as II experiment T. In contrast to this, a direct voltage of -200 V is applied to the control electrode 12 and a superimposed voltage of a direct voltage of -200 V and a AC voltage of 1 kHz and 800 V impressed on the sleeve 2a. The same results were obtained as in experiments R and T.

When using a two-component developer with the previous magnetic brush development processes have not made the particle size of the toner and carrier particles materially can be reduced, so that a reproduced or copied image of high quality cannot be obtained either.

In the method according to the invention, however, the control electrode to generate the oscillating electric field in the development zone and to control it Field arranged so that the toner particles can form a cloud within the oscillating electric field Accordingly, a toner with an average particle · * size of 1-20 μπι and a carrier with an average Particle size of 4-50 μm, preferably 5-50 μm, is used will. In this way, a reproduced image of satisfactory density and high density can be obtained Achieve tonal gradation and resolution.

-70-

Since a two-component developer is used (a multi-component developer can also be used the charge of the toner can be better stabilized compared to the toner in the one-component developer so that aggregation of the toner is less likely to occur.

Claims (23)

-1- I. Ρ2 .TENTAN S? Rl) CHE 1 J development process, characterized in that a developer containing carrier and toner particles is applied to a developer transfer carrier to form a developer layer, the developer layer is introduced into an oscillating electric field and a latent image generated on an image carrier within of the vibrating electric field is developed by means of the developer. 20th 2. The method according to claim 1, characterized in that that the mean particle size of the carrier particles is 4-50 µm. 25th 3. The method according to claim 1, characterized in that the mean particle size of the toner particles up to 20 μΐη. 4. The method according to claim 1, characterized in that the carrier particles are spherical or approximately spherical are formed (sphered). 5. The method according to claim 1, characterized in that the toner particles are spherical or approximately spherical are formed (sphered). 35 6. The method according to claim 1, characterized in that the carrier particles of magnetic particles and 341 • -2-covered with a thermoplastic synthetic resin. 7. The method according to claim 1, characterized in that that the toner particles consist of a toner for pressure fixing. 8. The method according to claim 1, characterized in that that a control electrode for controlling the flight of the toner particles in a development area between the developer transfer carrier and the image carrier. 9. The method according to claim 1, characterized in that the thickness of the developer layer is set smaller is called the distance between the transfer carrier and the image carrier. 10. The method according to claim 1, characterized in that that the developer layer is brought into contact with the image carrier. 11. The method according to claim 1, characterized in that one arranged in the developer transfer carrier rotatable magnet is used. 12. The method according to claim 1, characterized in that an oscillating electric field of a frequency from 100 Hz to 10 kHz is used. 13. The method according to claim 1, characterized in that the frequency of the oscillating electric field is preferably 1-5 kHz. 14. The method according to claim 1, characterized in that magnetic toner particles are used. -3- 15. The method according to claim 1, characterized in that non-magnetic toner particles are used. 16. The method according to claim 1, characterized in that magnetic carrier particles are used. 17. The method according to claim 1, characterized in that that carrier particles made of an insulating material with 8 13 greater than 10 ohm-cm and preferably 10 ohm-cm can be used. 18. The method according to claim 1, characterized in that carrier particles have an average particle size of 5 - 50 µm and toner particles of an average particle size of up to 20 µm can be used. 19. The method according to claim 1, characterized in that that carrier particles with an average particle size of 5 - 50 μΐη are used, which are spherical or are approximately spherical. 20. The method according to claim 1, characterized in that toner particles of an average particle size of up to 20 .mu.m, which are spherical or approximately spherical in shape (sphered) can be used. 21. The method according to claim 1, characterized in that the carrier particles are spherical or approximately spherical are formed and consist of magnetic particles and a thermoplastic synthetic resin. 22. The method according to claim 1, characterized in that toner particles have an average particle size of -4- 1 up to 20 μΐη can be used, which are spherical or are approximately spherical and consist of a toner for pressure development. 5 23. The method according to claim 2, characterized in that that carrier particles with an average particle size of 5-50 μm are used.