DE102011000815A1 - Arrangement for optimizing transfer of toner image on printing material by electrophoretic printing apparatus, has transfer unit provided with rotating transfer element - Google Patents

Abstract

The arrangement has a transfer unit (6) provided with a rotating transfer element (60). The transfer element absorbs carrier liquid with toner images from a charge image carrier (1). An alternating current charging electrode is arranged adjacent to the transfer element between the charge image carrier and transfer zone (9) in moving direction of the transfer element.

Description

For printing a substrate z. As a single sheet or a tape-shaped recording medium made of various materials, eg. As paper or thin plastic or metal foils, it is known on a charge image carrier, for. As a photoconductor, image dependent to generate charge images corresponding to the images to be printed, consisting of inked and non-inked areas. The areas to be inked of the charge images are visualized with a developer station on the charge image carrier by toner particles as toner images. Subsequently, the toner image thus produced is transferred to the printing substrate in a transfer printing zone and then fixed.

For coloring the charge images, a developer liquid having at least charged toner particles and carrier liquid can be used. Possible carrier fluids are u. a. Hydrocarbons or silicone oil.

A method for such electrophoretic printing in digital printing systems is e.g. B. off WO 2005/013013 A2 ( US 2006/0150836 A1 . DE 10 2005 055 156 B3 ) known. After the charge images of the images to be printed have been formed on the charge image carrier, they are colored by a developer station with toner particles into toner images. In this case, a silicone oil-containing carrier liquid with dispersed therein color particles (toner particles) is used as the developer liquid. The supply of the developer liquid to the charge image carrier can be effected by a developer roller, to which the developer liquid is fed by a inking roller. The toner images are then embedded embedded in carrier liquid by a transfer unit from the charge image carrier and transferred in a transfer printing zone on the substrate.

In this printing process using developer liquid is thus the process of electrophoresis for the transfer of toner particles in the carrier liquid z. B. via a transfer unit arranged in the transfer roller used for printing material. The solid, electrically charged toner particles migrate through the carrier liquid as a transport to the substrate, the transport can be controlled by an electric field between the transfer roller and the substrate. The prerequisite for this, in addition to the toner particle charge and the electric field, is the provision of a sufficiently thick carrier liquid layer through which the toner particles can migrate.

When transferring the toner image onto the substrate, it is a goal to discharge the toner particles onto the substrate together with as little carrier liquid as possible. The transfer process should work with a wide variety of types of substrates. The transfer of a layer of carrier liquid with embedded toner images from a first roll to a second roll, e.g. B. from a photoconductor roll to a transfer roller and from a transfer roller to the substrate, in particular by an elastomer roller as a transfer roller, is associated with problems, since the umzudruckende layer of carrier liquid has a high solids content (toner particles) which is compactly adhered to the transfer roller on the elastomer surface , In addition, the proportion of carrier liquid, which passes to the printing material should be as low as possible in order to ensure economical operation of the printing device. The effectiveness of the electrophoresis decreases but with increasing solids concentration in the carrier liquid, in particular in the region of the transfer printing zone on the substrate. This is especially critical for papers as a substrate, since here the carrier liquid immediately strikes into the paper.

The problem to be solved by the invention is to provide an arrangement for the transfer of toner images embedded in developer liquid to a printing substrate in an electrophoretic printing apparatus in which the transfer efficiency when transferring the toner images to the printing substrate is optimized.

This problem is solved according to the features of claim 1.

In order to improve the transfer of the developer liquid having toner images onto a printing substrate, a transfer unit with a rotating transfer element is provided, which takes over the carrier liquid with the toner images from a charge image carrier and transports it to a transfer printing zone in order to transfer the toner images onto the printing material. Between the charge image carrier and the transfer printing zone, an AC charge electrode, viewed in the direction of rotation of the transfer element, is arranged adjacent to the transfer element whose alternating electric field impinges on the transfer element and loosens the toner particles of the toner images in the carrier liquid on the transfer element before the toner images are transferred to the printing material.

Further developments of the invention will become apparent from the dependent claims.

It is advantageous if, after the AC charging electrode, viewed in the direction of rotation of the transfer element and in front of the transfer printing zone, a DC Charging electrode is arranged, through which the toner particles of the toner images are reloaded.

• – Durch die AC-Ladeelektrode, z. B. ein AC-Corotron, wird die kompaktierte Tonerpartikelschicht auf dem Transferelement gelockert, so dass der Umdruck der Tonerbilder auf den Bedruckstoff verbessert wird. Damit steigt der Transferwirkungsgrad des Umdrucks.
• – Die Abreinigung des Resttoners von dem Transferelement nach dem Umdruck wird erleichtert.
• – Eine Elastomerschicht auf dem Transferelement wird geschont und damit deren Lebensdauer verlängert.
• – Der Umdruck der Tonerbilder auf den Bedruckstoff wird wirtschaftlicher.

The printing device according to the invention thus has the following advantages:

• - By the AC charging electrode, z. As an AC corotron, the compacted toner particle layer is loosened on the transfer element, so that the transfer of the toner images is improved on the substrate. This increases the transfer efficiency of the transfer printing.
• - The cleaning of the residual toner from the transfer element after the transfer printing is facilitated.
• - An elastomer layer on the transfer element is spared and thus extends their life.
• - The transfer of toner images on the substrate is more economical.

With reference to an embodiment, which is illustrated in the figures, the invention will be further explained. Show it:

1 a schematic representation of an electrophoretic pressure device;

2 a schematic representation of a transfer unit, in which the invention is used.

1 shows the components of a printing system DS, as z. B. off DE 10 2005 055 156 B3 is known. Along a charge image carrier 1 , in 1 a photoconductor drum, is a regeneration exposure 2 , a charging station 3 , a character generator 4 , a developer device 5 , a transfer unit 6 for transferring the charge images developed to toner images onto a printing substrate 7 and an element 8th for cleaning the charge image carrier 1 arranged. The transfer unit 6 has a transfer roller as transfer element 60 , a counter pressure roller 61 and a cleaning unit 62 on. The developer device 5 exists z. B. from a developer roller 51 which are in contact with the charge image carrier 1 is arranged. With the developer roller 51 become the charge images on the charge image carrier 1 developed. This leads to the developer roller 51 the developer liquid at least from a carrier liquid and electrically charged toner the charge image carrier 1 to. The development takes place in a known manner. The developer liquid is z. B. the developer roller 51 through an anilox roller 52 with cups and bars over one on the anilox roller 52 arranged chambered doctor blade 53 fed. The developer liquid is from a mixing container 54 taken and by a pump 55 the chambered doctor 53 fed. The after development of the charge images on the developer roller 51 Remaining residual developer liquid is removed from a cleaning roller 56 cleaned and a container 57 also supplied excess developer liquid from the chambered doctor blade 53 is forwarded. The contents of the container 57 is via a pump 58 the mixing container 54 fed.

When transporting the developer liquid from the developer roller 51 to the substrate 7 The toner particles in the carrier liquid migrate over the charge image carrier 1 to the transfer element 60 and on the transfer element 60 to the transfer zone 9 ; in the transfer zone 9 The toner images are then in the carrier liquid from the transfer element 60 on the substrate 7 transfer-printed. The on the transfer element 60 residual toner remaining after transfer is passed through the cleaning unit 62 from the transfer element 60 away.

A problem with this process is especially the transfer of the toner images with the carrier liquid on the substrate 7 , This will be on hand 2 explained. In 2 In principle, the process of the printing process is shown. The from the character generator 4 on the photoconductor drum 1 Charge images generated by the developer station 5 dyed with toner from the developer liquid. The toner images are in 2 through the black dots 10 on the photoconductor drum 1 shown. The toner images 10 migrate to the transfer element 60 , here a transfer roller, while the toner images are compacted (toner images 11 ). The transfer element 60 transports the toner images 11 in the carrier liquid to the transfer zone 9 ; in the transfer zone 9 become the toner images 11 together with carrier liquid under the influence of an electric field on the substrate 7 transfer-printed. On the substrate 7 Finally, the toner images are in a fuser 16 fixed. To transfer the toner images 11 on the substrate 7 becomes the substrate 7 through the counter-pressure roller 61 to the transfer element 60 pressed, at the same time can between transfer element 60 and counterpressure roller 61 generate an electric field that is directed so that the toner particles of the toner images 11 to the substrate 7 to be pulled. The corresponding electrical potentials on the transfer element 60 and at the counterpressure roller 61 are known and in 2 therefore not shown. The following is called a transfer element 60 a transfer roller used, the transfer element may also be a transfer belt.

The toner images with carrier liquid are from the photoconductor drum 1 on the transfer roller 60 transfer. On the surface of the transfer roller 60 are thus the toner images 11 compacted arranged in the carrier liquid. If a transfer roller 60 z. B. is used with an elastomer layer on the surface, there is a strong adhesion of the compacted toner images 11 at the elastomer surface of the transfer roller 60 with the result that the transfer of toner images on the substrate 7 is of inferior quality. Furthermore, the cleaning the residual toner from the transfer roller 60 difficult or leads to a rapid wear of the surface of the transfer roller 60 ,

To the transfer of the toner images on the substrate 7 can improve, adjacent to the transfer roller 60 in front of the transfer zone 9 in the direction of rotation of the transfer roller 60 seen a DC recharging electrode 12 , z. A DC recharging corotron, which reloads the toner images to the polarity used in the development of the charge images, e.g. B. negatively charged toner to negative polarity. However, this measure is not sufficient to optimally transfer the toner images to the substrate 7 because of their adhesion to the transfer roller 60 because of the surface properties of the transfer roller 60 , z. B. because of the elastomer surface is prevented.

According to the invention is therefore proposed, before the transfer printing zone 9 in the direction of rotation of the transfer roller 60 seen adjacent to the transfer roller 60 at least one AC charge electrode 13 , z. As an AC corotron to arrange, the alternating field on the transfer roller 60 impinges and the toner particles of the toner images 11 on the transfer roller 60 loosens. Thus, the adhesion of the toner particles to the surface of the transfer roller becomes 60 lowered, so that the transfer of toner images 11 to the substrate 7 is improved. At the same time, the cleaning of the residual toner from the transfer roller 60 facilitates and thus the surface of the transfer roller 60 spared. The AC Corotron 13 Can with a DC Corotron 12 be combined, the toner images first to the alternating field of the AC corotron 13 be exposed and then through the DC Corotron 12 be charged to a potential favorable for transfer before the transfer zone 9 is reached.

The AC Corotron 13 can be connected to an AC source 14 with a voltage of z. B. 4 to 8 kV with a frequency of 3 to 6 kHz. The distance of the AC corotron 13 to the surface of the transfer roller 60 can z. B. 2 to 3 mm. On the DC Corotron 12 can be a DC voltage source 15 be connected. To the DC Corotron 12 In addition to the DC voltage, an AC voltage can be applied so that an alternating field and the field generated by the DC voltage are superimposed there. Then you can do without an AC-Corotron.

LIST OF REFERENCE NUMBERS

DS

printing device

1

Charge image carrier = photoconductor drum

2

regeneration exposure

3

charging station

4

character generator

5

developer station

6

transfer unit

7

substrate

8th

cleaning unit

9

transfer printing

10

toner image

11

Compacted toner image

12

DC corotron

13

AC corotron

14

AC voltage source

15

DC voltage source

16

fuser

51

developer roller

52

anilox roller

53

chambered doctor blade

54

mixing tank

55

pump

56

cleaning roller

57

container

58

pump

60

cleaning roller

61

Backing roll

62

cleaning unit

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2005/013013 A2 [0003]
• US 2006/0150836 A1 [0003]
• DE 102005055156 B3 [0003, 0015]

Claims (8)

Arrangement for optimizing the transfer of a toner image embedded in carrier liquid onto a printing substrate in the case of an electrophoretic printing apparatus, in which a transfer unit ( 6 ) with a rotating transfer element ( 60 ) is provided, the carrier liquid with the toner images ( 10 ) from a charge image carrier ( 1 ) as compacted toner images ( 11 ) and to a transfer zone ( 9 ) to the toner images ( 11 ) on the substrate ( 7 ), in which between charge image carrier ( 1 ) and transfer zone ( 9 ) in the direction of movement of the transfer element ( 60 ) seen an AC charge electrode ( 13 ) adjacent to the transfer element ( 60 ) is arranged, which is an alternating electric field to the transfer element ( 60 ) which generates the toner particles of the toner images ( 11 ) in the carrier liquid on the transfer element ( 60 ) relaxes. Arrangement according to Claim 1, in which the AC charging electrode ( 13 ) an AC corotron is provided. Arrangement according to Claim 2, in which the AC corotron is connected to an AC voltage source ( 14 ) with a voltage of 4 to 8 kV and a frequency of 3 to 6 kHz. Arrangement according to claim 1, 2 or 3, wherein between AC charging electrode ( 13 ) and transfer zone ( 9 ) adjacent to the transfer element ( 60 ) a DC Corotron ( 12 ) is arranged at which a DC voltage source ( 12 ) connected. Arrangement according to Claim 4, in which the DC corotron ( 12 ) is additionally connected to an AC voltage source, so that the DC corotron ( 12 ) generates an alternating field in addition to the field generated by the DC voltage. Arrangement according to one of the preceding claims, in which the transfer element ( 60 ) has an elastomeric coating on the surface. Arrangement according to one of the preceding claims, in which the transfer element ( 60 ) is a transfer roller. Arrangement according to one of Claims 1 to 6, in which the transfer element ( 60 ) is a transfer belt.

Images