EP1290502B1 - Applicator element and method for electrographic printing or copying using liquid colouring agents - Google Patents

Description

The invention relates to an applicator element and a method for electrographic printing or copying under Use of liquid colorants.

Known devices for electrographic printing or Copying uses a process in which dry toner runs on the latent image of a latent image carrier, for example a photoconductor is applied. Such a dry toner leads to relatively thick layers of toner because the Toner particles have a relatively large particle size and several toner particles for sufficient color coverage must be superimposed. The on the latent image applied dry toner layer must be fixed, which requires a relatively high energy. This high Energy leads to a high strain on the final image carrier, preferably paper, due to fixation by heat and / or pressure.

Liquid toners used so far contain a carrier liquid, which is odorless and flammable. The one with Final image carrier loaded with liquid toner is often also odorous. When using liquid toner it is brought into contact with the latent image carrier.

From US-A-5,943,535 it is known to be a water based working liquid toner to use that in contact brought with a latent image carrier. Because of the Conductive liquid toner results on the latent image carrier a precipitation corresponding to the electrostatic Charge image.

Furthermore, conventional printing processes such as for example offset printing, to refer to the liquid Use colorants. With these conventional printing processes the printing form is not variable, so that an economical Printing short runs is not possible.

DE-A-30 00 019 describes a device for one Liquid developer known. On a final image carrier generates a latent image, for example a potential pattern. An applicator element carries a layer of liquid. Between the liquid layer and the final image carrier becomes an air gap of a certain air gap width set. Liquid elements from the liquid layer are due to the electrical. Potential transferred to the surface of the final image carrier.

A method for printing is known from US-A-4,982,692, that works with a liquid developer. Droplets of a layer of liquid on an applicator element are under the action of an electrostatic Force field on the surface of a latent image carrier transferred.

Furthermore, from US-A-5,622,805 a method with a Liquid developer known to drop on an applicator roller under the influence of an electrostatic Field on the surface of a latent image carrier be transferred.

In US-A-4,942,475 and US-A-3,830,199 are liquid developer systems described in which an applicator roller carries a layer of liquid. The surface of the applicator roller contains a variety of recesses in which the liquid developer has been added.

From JP 10-18037 A with abstract is an image-generating Method known in which a contact surface is a carbon film having. This carbon film is made of DLC material, which is generated by a plasma CVD process.

It is an object of the invention, an applicator element and a method, in particular for electrographic printing or copying to indicate which application of a liquid colorant allowed.

This task is performed for an applicator element by the Features of claim 1 solved. Advantageous further training the invention are specified in the dependent claims.

The applicator element according to the invention is preferred in a printer or copier. In this is in prepared a coloring station liquid colorant in such a way that on the applicator element one per time and constant amount of liquid per area in the form of a liquid layer is available. On this applicator element, preferably a belt or a roller, the Liquid film in the area of effect of the potential pattern promoted, its potential according to one printing pattern is distributed. Preferably corresponds the potential pattern of an electrostatic charge image. The potential pattern was previously determined by suitable ones Generated means on the latent image carrier, for example by electrostatically charging and exposing a photoconductor. Between the surface of the liquid layer and the latent image carrier with the potential pattern exists an air gap. Between the surface of the applicator element and the image points of the potential pattern the latent image carrier has a potential contrast, for example, supported by applying a voltage to the applicator element. Sections of the liquid layer are then partially detached from the applicator element and jump in small droplets or transfer through Deformation of droplets according to the field lines the surface of the latent image carrier and color the latent image to the colorant image. This colorant image can then directly on the final image carrier, for example Paper. Another option is there in that the colorant image from the latent image carrier initially transferred to an intermediate carrier and from there is transferred to the final image carrier.

In the invention, a liquid colorant is preferred with a solids content of 20% or higher. This liquid colorant contains a carrier liquid, which are preferably odorless, non-flammable, is good for the environment and is not toxic. Preferably water is used as the carrier liquid.

The use of a liquid colorant has the advantage that it is easily kept in a storage container can and in this storage container and in the associated Transport lines no segregation, no phase separation and no irreversible drying occurs. By adding carrier liquid, the Solids concentration or the colorant concentration easily change. The liquid colorant can thus be supplied that a colorant concentrate and the carrier liquid stored and transported separately become.

Due to the injection of a defined excess charge into the droplets to be transferred when detaching them Droplets from the applicator element become an unintended one Avoid background coloring.

Between the surface of the applicator element and the There is an air gap on the surface of the latent image carrier, which is overcome by the liquid colorant. This coloring of the potential pattern on the latent image carrier over an air gap has the advantage that there is no wear on the latent image carrier Closure is at least minimized. When overcoming the Air droplets become the droplets according to the potential pattern focused, creating a sharp line results. The liquid colorant image is aligned automatically according to the potential pattern, which in particular allows a clear definition of the image edges.

The use of a liquid colorant has continued the advantage that relatively thin layers of paint on the final image carrier can be generated. In this way it is Colorant consumption low and high printing speeds achieve. Also in terms of fixation of the colorant image on the final image support yourself advantages. The energy to be used can be reduced and the processing speed can be increased.

The potential pattern on the latent image carrier is preferred designed as an electrostatic charge image. It However, it is also possible to create a potential pattern in the form of Generate magnetic field lines. In this case, it should liquid colorants magnetically influenceable carrier particles contain, which cause colorants on the latent image carrier transferred while overcoming the air gap and color the latent image. With the label "electrographic printing or copying" will expressed that a variety of electrical working Processes can be used with which a latent image is applied a latent image carrier can be generated.

According to an exemplary embodiment of the invention An alternating force field exists on the air gap the liquid layer acts. As an alternating one Force field can be an alternating electric field and / or a alternating magnetic field and / or alternating acoustic field, in particular an ultrasound field can be used. It has been shown in practice that such a Alternating field is advantageous to fine print structures too produce. The alternating force field supports the formation of droplets in the liquid layer or the Formation of small channels between the liquid layer and the surface of the latent image carrier.

The respective alternating field advantageously has a frequency Greater than or equal to 200 Hz, in particular a frequency of 1 kHz to 20 kHz, preferably a frequency of 1 kHz to 5 kHz. At the specified frequencies, a cheap one Get the print result.

According to an embodiment of the invention, the Gap width of the air gap depends on the pressure point resolution set. As a pressure point resolution is usually uses the measure dpi, i.e. "Dots-per-inch." Preferably the gap width is set so that it 2 times to 20 times the distance between the pixels in one predetermined pressure point resolution, in particular 5 times to 10 times the distance. At a Pressure point resolution of dpi = 600 is the distance between two pixels 42 µm. A favorable gap width of the The air gap is then around 200 µm.

A special meaning comes for a good printing result the surface tension and the viscosity of the liquid layer to. There are two embodiments A and B presented with different focal points of the parameters. In the first embodiment A becomes relative low surface tension and a relatively low Viscosity selected. The surface tension is typically in the range of 20 to 45 mN / m, in particular in the range of 25 to 35 mN / m. The associated viscosity is in the range of 0.8 to 50 mPa · s, especially in the range 3 to 30 mPa · s set. Through the above The values of the surface tension and the viscosity are the minimizes the energy required to train Liquid channels between the liquid layer the applicator surface and the surface of the latent image carrier is needed. At the same time, the set surface energy prevents the Liquid permanently at areas of the image that are not to be colored of the latent image carrier.

In the second embodiment, B is for the liquid a relatively high surface tension and a adjusted viscosity used. The surface tension is in the range of 50 to 80 for this example mN / m, preferably in the range from 55 to 70 mN / m. The viscosity has a value in the range of 0.8 to 300 mPa · s. With the selected values of surface tension and The viscosity of the liquid is formed on the surface easily removable liquid drops on the applicator. These drops stick due to the high surface tension the liquid does not appear on image areas on the latent image carrier that are not to be colored. By customization the viscosity gives the property of the drops, that in collisions between drops, a Drops and the surface of the latent image carrier or Drops and applicator surface mostly too elastic Deformation of the drops is coming; an agglomeration the drop or wetting of the surface of the latent image carrier in areas of the image that are not to be colored, is avoided.

According to another aspect of the invention, a method to provide a layer of a liquid colorant, especially for electrographic printing or Copy, specified.

Figur 1

schematisch den Aufbau einer Drukkeinrichtung, die mit flüssigem Farbmittel arbeitet,

Figur 2

eine Einfärbestation mit einer Applikatorwalze für die Bereitstellung einer dünnen Flüssigkeitsschicht,

Figur 3

das Prinzip des Übertragens von Tröpfchen von der Flüssigkeitsschicht auf dem Applikatorelement auf die Oberfläche des Latentbild-Trägers,

Figur 4

ein Beispiel für den Aufbau der Oberfläche des Applikatorelements, wobei sich ein Tröpfchen-Teppich an der Oberfläche ausbildet,

Figur 5

die Ausrichtung des flüssigen Farbmittels auf der Oberfläche des Latentbild-Trägers entsprechend einem Ladungsbild,

Figur 6

eine alternative Ausführungsform für eine Einfärbstation,

Figur 7

die Oberfläche einer Applikatorwalze mit kontinuierlichen Eigenschaften und der Ausbildung einer gleichmäßigen Flüssigkeitsschicht,

Figur 8

eine Deckschicht einer Applikatorwalze mit ersten Bereichen erhöhter elektrischer Leitfähigkeit,

Figur 9

eine Deckschicht einer Applikatorwalze mit zweiten Bereichen geänderter Oberflächenenergie,

Figur 10

eine Deckschicht einer Applikatorwalze mit dritten Bereichen mikroskopischer Erhebungen,

Figur 11

stochastisch verteilte mikroskopische Erhebungen,

Figur 12

eine Deckschicht mit einer Kombination erster Bereiche und zweiter Bereiche,

Figur 13

eine Kombination von ersten Bereichen und dritten Bereichen,

Figur 14

eine Deckschicht einer Applikatorwalze, auf der zweite Bereiche und dritte Bereiche miteinander kombiniert sind,

Figur 15

eine Deckschicht, bei der erste Bereiche, zweite Bereiche und dritte Bereiche miteinander kombiniert sind,

Figur 16

eine Übersicht über mögliche Oberflächenstrukturierungen und deren Kombinationen,

Figur 17

die Oberflächenstruktur einer Applikatorwalze mit einer regelmäßigen Näpfchenstruktur,

Figur 18

eine Applikatorwalzenoberfläche mit einer Näpfchenstruktur und erhabenen Inseln,

Figur 19

eine Oberflächenstruktur mit einer stochastischen Verteilung von Näpfchen und mit freiliegenden Spitzen mikroskopischer Erhebungen,

Figur 20

ein Ausführungsbeispiel einer Reinigungsstation,

Figuren 21 bis 26

verschiedene fotodielektrische Bilderzeugungsprozesse zum Erzeugen eines latenten Bildes.

Embodiments of the invention are explained below with reference to the drawing. It shows:

Figure 1

schematically the structure of a printing device that works with liquid colorant,

Figure 2

a coloring station with an applicator roller for providing a thin layer of liquid,

Figure 3

the principle of transferring droplets from the liquid layer on the applicator element to the surface of the latent image carrier,

Figure 4

an example of the structure of the surface of the applicator element, a droplet carpet being formed on the surface,

Figure 5

the alignment of the liquid colorant on the surface of the latent image carrier in accordance with a charge image,

Figure 6

an alternative embodiment for a coloring station,

Figure 7

the surface of an applicator roller with continuous properties and the formation of a uniform liquid layer,

Figure 8

a cover layer of an applicator roller with first areas of increased electrical conductivity,

Figure 9

a cover layer of an applicator roller with second areas of changed surface energy,

Figure 10

a cover layer of an applicator roller with third areas of microscopic elevations,

Figure 11

stochastically distributed microscopic surveys,

Figure 12

a top layer with a combination of first areas and second areas,

Figure 13

a combination of first areas and third areas,

Figure 14

a cover layer of an applicator roller, on which second areas and third areas are combined with one another,

Figure 15

a cover layer in which first areas, second areas and third areas are combined with one another,

Figure 16

an overview of possible surface structures and their combinations,

Figure 17

the surface structure of an applicator roller with a regular well structure,

Figure 18

an applicator roller surface with a well structure and raised islands,

Figure 19

a surface structure with a stochastic distribution of cells and with exposed tips of microscopic elevations,

Figure 20

an embodiment of a cleaning station,

Figures 21 to 26

Various photo-dielectric imaging processes for creating a latent image.

Figure 1 shows an embodiment of the invention Printing device having an end image carrier 10, for example Paper, printed. The final image carrier 10 is in the direction of arrow P1 moves. The printing device comprises a photoconductor drum 12, which is in the direction of the arrow P2 turns. One applied to the photoconductor drum 12 Colorant image is placed on an intermediate carrier drum 14 transferred in contact with the photoconductor drum 12 stands. The intermediate carrier drum 14 rotates in the direction the arrow P3 and transfers the colorant image supports through a reloading corotron 16 to the lower side of the final image carrier 10.

An exposure station is located on the circumference of the photoconductor drum 12 18, a corotron 20, a light source 22 for generation a latent image on the photoconductor drum 12, a coloring station 24 with an applicator roller 26 Hot air generator 28, a cleaning station 30 and one Regeneration station 32 arranged. The functions of this Units 18 to 32 are explained in more detail below.

There is another on the circumference of the intermediate carrier drum 14 Cleaning station 34 and a hot air station 35 are arranged. The further cleaning station 34 can be constructed in this way be like cleaning station 30.

Figure 2 shows an embodiment of the coloring station 24 with the applicator roller 26, the outer surface of the Facing photoconductor drum 12. The applicator roller 26 becomes a uniform liquid film over a feed roller 36 38 fed. This feed roller 36 in turn is over a scoop roller 40, which is on its outer circumference has a structure with wells 42, a constant over time Amount of colorant supplied. The scoop roller 40 dips with a section in a scoop 44 in which a stock of colorant is included.

A doctor blade 46 acts on the outer circumference of the scoop roller 40, which causes only the volume contained in the well 42 of colorants is promoted. The feed roller 36 is deformable. The wells empty on their surface 42 so that 36 on the surface of the feed roller the smooth liquid film 38 forms. This liquid film 38 is brought up to the applicator roller 26.

The feed roller 36 can run in the same direction or in the opposite direction turn to the applicator roller 26. Preferably move Applicator roller 26 and feed roller 36 in synchronism, such as is shown in Figure 2 by the direction arrows. The Applicator roller 26 separated from the smooth liquid film 38 a homogeneous droplet carpet 48, the droplets under the action of an electric field from the Surface of the applicator roller 26 according to the image pattern skip to the photoconductor 12, such as this shown with the aid of the droplet 50 in FIG is. The droplet 50 overcomes one Air gap L, preferably in the range of 50 to 1000 microns is in the range of 100 to 200 µm. The surface the photoconductor 12 can run in the same direction or in opposite directions move to the surface of the applicator roller 26. The surface speed of these two elements can be the same size or different. Preferably move the surfaces of the photoconductor 12 and the Applicator roller 26 at the same speed in the same direction, as shown in Figure 2. The remains of the droplet carpet 48 with the help of a squeegee 52 of the Surface of the applicator roller 26 removed and over Line system 54, 56 the colorant in the scoop 44th fed again. Another doctor blade 58 removes the liquid film 38 on the feed roller 36 and leads over the Element 56 the remains of the colorant in the tub 44.

To support the transfer of droplets 50 from the Surface of the applicator roller 26 on the surface of the The photoconductor 12 is the applicator roller 26 with a bias potential UB applied in the form of a DC voltage. Because of this bias potential UB between Image locations on the photoconductor 12 and the bias potential UB a potential contrast. The bias potential UB can additionally an AC voltage with a frequency of preferably 5 kHz or higher can be superimposed.

The potential pattern on the photoconductor 12 is labeled UP. This potential pattern UP is called a charge image for example using a conventional electrographic Processes by charging with a Korotron 20 (see FIG. 1) and by partial discharge using a Light source 22, for example an LED print head or a laser printhead.

At the image points defined by the potential pattern UP it is due to the surface of the photoconductor 12 the potential difference to a charge shift within the drops of liquid in the droplet carpet 48 and consequently for the detachment of drops, for example the Drop 50. When detaching, there is also an excess charge injected into the drop. Due to the effect of electric field and the kinetic momentum moves the drop 50 becomes and becomes the photoconductor surface through the field lines to the image areas to be developed focused.

Alternative embodiments for a coloring station can use an anilox roller with a chambered doctor blade as a scoop roller to have. Another alternative provides that a smooth liquid film sprayed onto the feed roller becomes. Another alternative embodiment provides that the applicator roller with a section in a bath with immersed in the colorant, and that the dosage of the absorbed Liquid quantity via an elastic roller doctor takes place, which on the surface of the applicator roller acts. Other alternative embodiments of the coloring station are explained below.

FIG. 3 shows further details in the area of the air gap L between the surface of the photoconductor drum 12 and the surface of the applicator roller 26. In this example, the surface of the applicator roller 26 has a regular structure with elevations 60 with a height of approximately 5 to 10 μm and one Distance of approx. 10 to 15 µm from each other. These elevations 60 have a higher surface energy and a lower specific resistance than the surface sections 62 surrounding them. The surface energy of the elevations 60 is preferably in the range from 40 mN / m, the specific resistance is preferably in the range from 10 ¹ to 10 ⁶ Ωcm. The surface sections 62 have a surface energy preferably in the range less than 20 mN / m and a specific resistance of preferably greater than 10 ⁷ Ωcm. The droplets of the droplet carpet 48 shown in FIG. 3 form on the elevations 60. After the droplets have been transferred to the surface of the photoconductor 12 as a result of electrical field forces of the potential pattern UP, the droplets, for example the droplets 62, accumulate over the path x corresponding to the potential UP, as is shown in detail in section 64.

Figure 4 shows an example of a section of the surface the applicator roller 26 with the elevations 60 and the surface sections 62. The droplets 66 form on the Surveys 60. These droplets have a size of 0.3 to 50 µm in diameter. The droplets 66 have a relatively low liability and get under the Eion flow of an external electric field (not shown) an increased electrical excess charge on the Surface. Such an external electric field will e.g. of those defined by the charge image, with colorants image areas to be colored, which are during the coloring is in the vicinity of elevations 60, e.g. at a distance L according to FIG. 2. The detachment through the effect of a latent charge pattern facilitated. The drop size can change by changing the structure size of the structuring of the surface varies become. The droplet size is the same or smaller than the print resolution, preferably the Drop diameter about a quarter of the smallest to be printed Picture element.

FIG. 5 shows the distribution of the photoconductor 12 transferred drop or several drops accordingly the charge pattern and the field strength E. That with colorant Image element 70 to be colored is through in this example the negative charges on the surface of the photoconductor 12 defined. The one transferred to this image point 70 Colorant 68 in the form of one or more droplets Droplet aligns itself according to the charge pattern, In particular, picture edges are sharply reshaped.

The surface energies of the photoconductor 12 and the liquid Colorants 68 are adjusted so that there is a contact angle of greater than approx. 40 ° results.

FIG. 6 shows a further variant of a coloring station 24. In this case, the applicator roller 26a does not carry a carpet of droplets due to continuous, homogeneous surface properties, but rather a continuous layer of colorant 72. The surface energy of the surface of this applicator roller 26a is typically in the range from 10 to 60 mN / m, preferably between 30 and 50 mN / m. The specific resistance of the surface is in the range from 10 ² to 10 ⁸ Ωcm, preferably between 10 ⁵ to 10 ⁷ Ωcm. A smooth liquid film with a thickness in the range from 5 to 50 μm, preferably 15 μm, is produced on the applicator roller 26a. This liquid film 72 is brought into the effective range of the potential pattern UP. At the image points defined by the charge image, a charge shift occurs within the liquid layer due to the potential contrast and, as a result, drops are formed and detached, as shown for example with the aid of the drop 50. When detaching, an excess charge is also injected into the drop 50, in a manner similar to that explained in FIG. Due to the field effect and the kinetic pulse, the drop 50 moves to the surface of the photoconductor 12 and is focused by the field lines on the image areas to be developed. The further structure of the coloring station 24a corresponds to the coloring station 24 shown in FIG. 2.

Figure 7 shows a representation similar to Figure 3, however using the smooth homogeneous liquid film 72, from the droplet 50 according to the distribution of the potential pattern UP can be extracted. Here too several droplets collect on the image point 74 to color this image area. Because of the abscissa direction x existing potential pattern UP (x) results a focus of the colorant on those to be developed Image passages 74. Due to the interaction between the electric field strength, surface tension and Micro-charge distribution on the colorant 62 is directed the liquid colorant 62 on the photoconductor 12 to the Field strength edges, whereby an anti-aliasing of the Picture elements results. The surface of the photoconductor 12 should have a surface energy that is not complete Spreading the liquid colorant 62 leads i.e. The colorant does not run apart.

FIGS. 3 and 7 show that the droplets of the surface of the applicator roller 26 or 26a on it Jump over the opposite surface of the photoconductor 12. Such jumping does not necessarily have to to be available. A drop of the drop carpet 48 on the Applicator roller 26 or a smooth liquid film 72 forming drop on the applicator roller 26a can be due to the electrical field influence according to the potential pattern UP to be elongated. This deformation of the drop can be such that for a a liquid channel between the surface for a short time of the photoconductor 12 and the surface of the applicator roller 26 or 26a forms and the drop can both at the same time Contact with the surface of the photoconductor as well with the surface of the applicator roller 26 or 26a. As a result of the existing surface forces, it then migrates Drops completely or partially from the surface of the Applicator roller 26 to 26a over to the surface of the photoconductor, which leads to a pictorial coloring comes.

In the following Figures 8 to 19, the structure and technical properties of the surface of the applicator roller 26 explained. In principle, the applicator element is regardless of what shape it is, that its surface is a structure with a variety from areas where droplets are coming off the liquid layer is relieved. This layer of liquid can be present as a homogeneous, uniform layer or as a droplet carpet, as already mentioned above has been mentioned.

The applicator roller 26 according to FIG. 8 has a cover layer 76 with reduced conductivity and surface energy in the range of preferably 30 to 50 mN / m a relatively low polar portion of the surface energy, is preferably in the range of less than 10 mN / m. A large number of first regions are in this cover layer 76 78 embedded, one opposite the top layer 76 have increased electrical conductivity. The first areas 78, for example, by doping the top layer 76 generated by means of metal atoms. The first areas 78 can repeat at regular intervals, or arranged at stochastically distributed intervals his. The distances between the first regions are preferably 78 at a distance of 0.3 to 50 µm from each other.

In the areas left free by the first areas 78 80, the surface energy is increased, so that there There is a tendency to form droplets. The top layer can, for example, from the material DLC (diamont like carbon). The doping of the first regions 78 can be done in this way be chosen so that an almost rectangular transition of Conductivity is present. Alternatively, a soft, continuous transition can be selected. The Art of the transition and also the size of the first areas 78 and the exposed areas 80 define the size the droplet. This way droplets can be created be that have a diameter up to a maximum of 10 microns and can be easily detached from the areas 80.

The advantage of the arrangement shown in Figure 8 is in that the structuring of the top layer 76 with areas 78 different conductivity on one other smooth surface can be done. In the first areas 78 increased conductivity can be an injection of charge carriers into the colorant droplets, which the Detachment of droplets or drops from a closed one Liquid film under the influence of an external one electrical field support.

FIG. 9 shows a further variant of the structuring of the Surface of the applicator roller 26. Same reference numerals denote the same elements, as for the following Figures is retained. In the embodiment according to Figure 9 is structured by sections Changing the surface energy. This change in surface energy takes place in a fixed grid and abruptly. In a variant, the transition between sections different surface energy and that Grid can be distributed stochastically. In the top layer 76 made of a first material are embedded in cups 84, their grid-like distribution with a resolution of preferably 1200 dpi. The cups 84 are with filled with a second material. The cup 84 with the second material form second regions 86 in the surface of the cover layer 76 with exposed ones in between Areas 80. Forms at those areas left blank a droplet carpet with droplets 82.

The combination of two materials allows a variety of variations. For example, ceramic can be used as the first material and Teflon can be provided as the second material. Farther can be the first material DLC material, F-DLC material (fluor diamond like carbon material) or Sicon material and Teflon can be provided as the second material. Another Material combination results when the first material a Ni layer or a layer of Ni alloy, preferably CrNi, and provided as a second material Teflon is, wherein preferably the Teflon material in the form of balls is embedded in the Ni layer.

The advantages of the arrangement according to FIG. 9 are that the structuring on an otherwise smooth surface can be done. The change in surface energy leads specifically to the promotion of drop formation. about is the numerous variants of material combinations an adaptation to different colorant systems possible. The combination of materials also enables the Adhesion of the droplets formed on the surface of the applicator roller to reduce.

FIG. 10 shows a further example of a structuring the surface of the applicator roller 26 such that the Formation and detachment of drops from the liquid layer is relieved. The structure of the surface has a variety of third areas 88 called microscopic Elevations on the otherwise macroscopically smooth Surface are flattened. These third areas 88 can form a regular or a stochastic structure. The spatial wavelength of this structure is preferably in the range from 0.3 to 50 µm. The material of the top layer should be such that it matches the one used liquid colorants have the largest possible contact angle forms, preferably a contact angle larger 90 °. A discontinuous layer of liquid is thus formed, preferably in the form of drops on the Interface of the liquid with the surface of the applicator roller 26 out. The microscopic elevations form small ones Tips and edges that are in the range of an electrical Field for the formation of electrical field peaks to lead. These field peaks serve as replacement points for the Transfer of drops.

Figure 11 shows that the third areas 88 are stochastic can be distributed. The difference in height between the highest points of the microscopic elevations of the third Areas 88 and the level of macroscopically smooth The surface area for the examples according to FIGS. 10 and 11 approx. 2 to 20 µm, preferably 5 to 10 µm.

FIG. 12 shows an example in which first areas 78 and second areas 86 are combined with one another. Both areas 78, 86 are formed in the same locations. alternative can the transition between the combined first and second areas 78, 86 and the remaining areas 80 be continuous and the areas can be stochastically distributed his. The combination of materials can be such as has been explained in connection with Figure 9.

Figure 13 shows a surface structure as a combination the examples of Figures 8 and 10. First areas 78 with increased conductivity with a change in the surface contour combined. The first areas 78 and the third areas 88 can be formed regularly and alternately his. The spatial wavelength of the first areas 78 and the third regions 88 can, however, also be separated from one another deviate, the local wavelength of the third areas 88 at most one fifth of the local wavelength of the first areas Is 78. Because of the combination of the first areas 78 and third areas 88 the droplet formation, the size of the droplets and the injection of charge carriers be affected in these drops.

Figure 14 shows an embodiment in which the surface is structured such that second areas 86 and third areas 88 are combined with one another. This second areas 86 and third areas 88 may be regular and be trained alternately. Alternatively, you can the spatial wavelengths of the second regions 86 and the third Regions 88 may be different from one another, the Spatial wavelength of the third areas 88 at most one fifth the local wavelength of the second regions 86.

Figure 15 shows another embodiment in which first areas 78, second areas 86 and third areas 88 are combined. In this way, the wetting of the Surface of the applicator roller 26 can be set specifically.

Figure 16 gives an overview of the possible surface structures and their combinations. In the top one Illustration shows that the top layer of the applicator roller first areas 78 with changed conductivity Has. The liquid colorant is in the example below Figure 16 drawn as a continuous layer 77.

The example below shows the second areas 86 with changed surface energy, the cup-shaped are. The example below shows the Surface structure with the third areas of a microscopic regular surface contour. The underlying one Example shows a stochastically distributed surface contour with third areas 88. The underlying another example shows a surface structure with a combination of first areas 78 and second areas 86. The further example below shows a combination of first areas 78 of changed conductivity and third areas 88 with a microscopic Surface contour. The penultimate example shows the Combination of second areas 86 and third areas 88. The last example shows a surface structure with a combination of first areas 78, second areas 86 and third areas 88.

Figures 17 to 19 show concrete surface structures for an applicator roller. 17 is on one metallic base body 90 a cover layer 76 with reduced Conductivity and a surface energy in Range from 30 to 50 mN / m with a polar portion larger equal to 5 mN / m, e.g. Ceramic applied. This top layer 76 has a regular well structure, for example with a resolution of 1200 dpi. The cups 84 are off a material with a lower surface energy than ceramics and with lower conductivity than ceramics, e.g. Teflon, filled up. Overall, there is a flat roller surface. The surface of the filled cells has an area ratio of 60 to 90%, preferably 70 up to 80% of the total surface. At the contact point between feed roller 36 and applicator roller 26 (see FIG 2) the liquid film 38 is split. On the applicator roller 26 only take the areas of the surface liquid who have increased surface energy. There these areas with increased surface energy from areas are separated with lower surface energy, an even droplet carpet is formed 48. The drop size is due to the fineness of the structure determined from hydrophobic and hydrophilic areas. at With a resolution of 1200 dpi, drops of approx. 10 to 15 µm in diameter.

Figure 18 shows another example of the structuring the applicator roller surface. On the metallic Base body 90 with a surface energy in the range of preferably 30 to 50 mN / m with a larger polar portion Zero is a cover layer 76 with reduced conductivity, e.g. Ceramic, with a thickness of 1 to 500 µm applied. The base body 90 or optionally the cover layer 76 has a regular well structure structured with a resolution of at least 1200 dpi. The Cups 84 are lower with a material Surface energy than ceramics and lower conductivity as ceramics, e.g. Teflon, filled up. The cells 84 are not completely filled, so that there is a roll surface forms with raised islands 92. The surface the filled cup has a surface area of 60 to 90% of the total surface. On the sublime Points 92 form upon contact with the feed roller 36 Droplets 82 to form a droplet carpet 48.

Figure 19 shows a further embodiment of a Applicator. On the conductive base body 90, preferably made of metal, with a surface energy in the range from 30 to 50 mN / m with a polar portion larger an intermediate layer 76 is optionally equal to 5 mN / m reduced conductivity and a surface energy in the same area, e.g. Ceramic, with a thickness in the range from 1 to 500 µm applied. The surface of the roller body 90 or optionally the intermediate layer 76 structured by a stochastic distribution of cells 84 with a grid spacing of 0.3 µm to 50 µm, preferably in the range from 0.3 µm to 20 µm. A top layer 94, e.g. made of Teflon, with a material with lower surface energy and lower conductivity than the one below Layer 76, 90 fills the wells, so that the peaks 96 of the stochastic surface structure remain uncovered. The surface of the filled-in wells has an area ratio of preferably 60 to 90 % of the total surface. At the exposed tips 96 36 droplets form on contact with the feed roller 82 to form a droplet carpet 48.

Further assemblies of the printing device shown in FIG. 1 are described below. After the latent image has been colored on the photoconductor drum 12, the colorant image is thickened by physical and / or chemical processes, preferably by evaporation of the carrier liquid in the colorant. This effect is intensified by the hot air generator 28, to which the colored ink image is fed as a result of the rotational movement of the photoconductor drum 12. In the example shown in FIG. 1, the colorant image is first transferred from the surface of the photoconductor drum 12 to the surface of an intermediate carrier drum 14 which is in contact with the surface of the photoconductor drum 12. The transmission takes place by mechanical contact and is preferably supported by a transfer printing voltage which is applied to the intermediate carrier drum 14. When the colorant image is transferred, the layer thickness of this colorant image is evened out; there is a smoothing. The intermediate carrier drum 14 consists of an electrically highly conductive body, preferably made of metal, and has a coating with a defined electrical resistance, preferably in the range from 10 ⁵ to 10 ¹³ Ωcm.

Alternatively, instead of the intermediate carrier drum 14, a band can be provided as the intermediate carrier, which has a defined electrical resistance, preferably in the range from 10 ⁵ to 10 ¹³ Ωcm, and that of an electrically highly conductive element, which preferably consists of a metal, to the colored one Image on the latent image carrier, for example the photoconductor drum 12, is brought up. This tape, too, preferably carries an electrical potential on the surface, which supports the transfer of the liquid image from the latent image carrier to the intermediate carrier. The electrical potential of the surface of the intermediate carrier is set by an auxiliary voltage which is applied directly to the intermediate carrier or to the electrically highly conductive element which leads the intermediate carrier surface to the colored image on the latent image carrier. This auxiliary voltage can contain DC voltage components and AC voltage components.

At the transfer point from the latent image carrier to the intermediate carrier, for example the intermediate carrier drum 14, The following relation results with regard to the adhesive forces: The cohesion of the colorant image is greater than the adhesion between intermediate carrier and colorant image; the adhesion between the intermediate carrier and the colorant image greater than the adhesion between the surface of the latent image carrier and the colorant image. Based on these The colorant image of the latent image carrier becomes adhesive force conditions transferred to the intermediate carrier.

Suitable means, preferably, can be attached to the intermediate carrier through a dry stream of hot air, the viscosity of the transferred colorant image can be further increased. This ensures that the cohesion of the colorant image is high enough to be a complete To ensure transfer to the final image carrier 10. This also ensures that in the operating mode "Collection mode", which is explained in more detail below, the last colorant image generated is a lower one Cohesion than the previously collected colorant images having. In this way there is no retransmission of colorant on the surface of the photoconductor.

According to FIG. 1, to generate a dry hot air stream, on the surface of the intermediate carrier drum 14 acts, a hot air station 36 is provided. At this the surface of the intermediate carrier drum 14 in the direction of rotation P3 passed.

On the circumference of the photoconductor drum 12 or the intermediate carrier drum 14 is a cleaning station 30 or a cleaning station 34 arranged. These cleaning stations 30, 34 are used to remove the remains of the after printing remaining colorant image. The structure of the Cleaning station 30 and 34 will be explained in more detail below. Furthermore, on the circumference of the photoconductor drum 12 after the cleaning station 30, a regeneration station 32 arranged on the surface of the photoconductor drum 12 defined surface properties and charge injection ratios generated.

For realizing multi-color printing on the final image carrier 10 different operating modes can be provided his. In a first operating mode, different Color image separations one after the other on the latent image carrier, i.e. the photoconductor drum 12, generated and successively transferred directly to the final image carrier 10.

In a second operating mode, several color image separations superimposed on the photoconductor 12. The overlaid color image separations are then together on the End image carrier 10 transmitted.

A third mode of operation provides that to implement a Multi-color printing several color separations in succession generated on the latent image carrier and on the intermediate carrier be overlaid. The overlaid color image separations are transferred together from the intermediate carrier to the final image carrier 10 transferred.

In a fourth operating mode, there is an extract for each color image a printing unit with a latent image carrier and a Applicator element provided, each a color separation produce. The different color separations are sequential transferred directly to the final image carrier 10 with a precise fit or first on an intermediate carrier, e.g. the intermediate carrier drum 14, transferred and from there to the final image carrier 10 transferred. This operating mode is also called single-pass procedure called.

A fifth operating mode is characterized in that a single latent image carrier for realizing multi-color printing is provided, the several applicator elements, assigned for example by the type of applicator roller 26 are. Each applicator element creates a color image extract, the one on the final image carrier 10 directly or initially onto an intermediate carrier and from there onto the final image carrier 10 is transmitted. This mode is also Called multi-pass procedure.

An embodiment for the single pass method has up to five complete printing units, each with a character generator, a latent image carrier and at least one coloring station, and has a common one Subcarrier. The multicolored image is in one single pass generated. The individual partial color images for this purpose on the latent image carriers assigned to them generated at such a time interval that they are in register on the same surface area of the intermediate carrier meet, one at a time colored on the individual Latent image carriers are moved past and in contact with these takes over the partial color images. In the overlay the partial color images form together on the intermediate carrier the mixed color image. The cohesion of the individual Colorant images are on the respective latent image carrier set so that the cohesion of the first on the colorant image transferred to the intermediate carrier is higher as the following colorant image. For example can be done by a differently advanced The colorant images are dry become.

Figure 20 shows an embodiment for the cleaning station 30. This cleaning station 30 has the task that that remained after the transfer of the colorant image Remains 101 of the colorant image from the surface the photoconductor drum 12 can be removed. In the shown For example, a brush roller 102 is used for this, whose brush 103 with the surface of the photoconductor drum 12 is in contact. The brush roller 102 rotates in the direction of the rotary arrow P4 preferably in opposite directions to the movement the photoconductor drum 12 in the direction of P3. The brush 103 is arranged such that the theoretical outer diameter the brush roller 102 into the surface of the photoconductor drum 12 dips. This ensures the defined Stress on the bristles and the compensation of Manufacturing tolerances. The brush roller 102 removes residues 101 of the liquid colorant by mechanical displacement, supported by the adhesion between colorants and the brush hair and possibly by an electrostatic Support. The basic body of the brush roller 102 is preferably made of metal to which one Voltage UR is applied to the advantageous electrostatic To achieve peeling effect. This voltage is UR a DC voltage superimposed by an AC voltage can be. The brush 103 passes through after contact with the photoconductor drum 12 a bath 106 in a tub 100, which preferably carrier liquid of the colorant contains to the remains of colorant in this carrier liquid to solve. It is advantageously used for detachment the colorant residue from the brush 103 the contact area between brush and carrier fluid with ultrasonic energy an ultrasound source 107 is applied. After this Leaving the bath 106, a suction device engages in the brush 103 104 a, the one on the brush 103 still sucks off adhering liquid residues. That in the tub 100 existing mixture of carrier liquid and residues Colorant can be processed and reused for the printing process become.

The cleaning station 30 shown in FIG. 20 removes residues 101 from the photoconductor drum 12. An identical or Similar cleaning station can also be used for cleaning the surface of an intermediate carrier, for example the intermediate carrier drum 14 can be used. Generally can remove such a cleaning station of paint residue on one commonly referred to as an image carrier Adhesive carrier on which a liquid colorant image has been applied.

Numerous modifications of the cleaning station are possible. For example, the cleaning station can have a detaching roller included, which to the surface of the image carrier is pressed. A squeegee that rotates in the direction of rotation Peeling roller seen after the contact point is arranged, is used to wipe off the pick-up roller Colorant. The release roller is preferably immersed in Bath with a carrier liquid. After going through the Bades can be another squeegee on the circumference of the peeling roller arranged to hold the liquid on the surface of the To strip the release roller. The surface energy of the surface the release roller should be set such that between the colorant residue and the surface of the release roller there is higher adhesion than cohesion within the colorant residue. The cohesion within the Colorant residue should increase the adhesion between the Colorant residue and the surface of the image carrier.

Another embodiment of the cleaning station contains a cleaning fleece that is pressed onto the image carrier. Preferably, the cleaning fleece is considerably less Speed moves as the peripheral speed of the image carrier. The cleaning fleece can be used as an endless belt be formed, which after contact with the Surface of the image carrier by means of a carrier liquid filled bathroom. The colorant is dissolved in this way and removed from the cleaning fleece. The endless belt will applied with a doctor blade and preferably with ultrasound. After leaving the bath will be excess Carrier liquid removed from the endless belt, preferably with the help of a pair of nip rollers.

Alternatively, the cleaning fleece can be placed on a dispenser roll be rolled up, and is using a roller and a Saddle brought into contact with the surface of the image carrier. Then the cleaning fleece is placed on a Receiver roll wound up. The cleaning fleece is from the donor role gradually moves to the recipient role. Between two steps can be up to several thousand Sheets are printed.

In another alternative the cleaning station contains this is a squeegee that is pressed against the image carrier is. If the image carrier is in the form of a ribbon, can be used as a counter bearing for the squeegee Rod may be provided.

In another embodiment of the cleaning station it contains a swimming pool facility, the one Spray with cleaning liquid onto the surface of the Image carrier judges. As a cleaning liquid is preferred the carrier liquid of the colorant used.

Another variant of the cleaning station contains one Roller bath facility using a roller cleaning fluid brings to the surface of the image carrier. This cleaning liquid, preferably the carrier liquid of the colorant, dissolves the colorant residues with the roll rotation can be removed. On the said The roller then acts on a doctor blade, which is the dissolved liquid Colorant strips off.

Another variant of the cleaning station contains a Airknife. This displaces the liquid colorant from to cleaning image carrier. The displaced colorant residues can be collected, processed and for the printing process be reused.

Another embodiment of a cleaning station contains a suction device that contains the liquid colorant residue aspirated from the surface of the image carrier. The Extracted exhaust air can be filtered and the liquid colorant be deposited, which is preferably in the further Printing process is reused.

Can optionally be seen in the direction of movement of the image carrier arranged in front of the cleaning station 30 be (not shown) that on the surface of the Applying a cleaning liquid to the image carrier. For application a scoop roller can be provided; alternative a section of the image carrier can be a bath with cleaning liquid run through. It is advantageous if as a cleaning liquid the carrier liquid of the colorant is used. It is advantageous if the contact point between cleaning liquid and image carrier with ultrasonic energy is acted upon.

According to Figure 1 is in the embodiment shown in Direction of rotation of the photoconductor drum 12 seen after the Cleaning station 30 arranged a regeneration station 32. While the cleaning station 30 is a continuous ensures mechanical cleaning, the regeneration station is used 32 the setting and the permanent warranty defined process conditions, especially regarding the surface properties, such as the surface energy of the latent image carrier, the surface energy ratio between the surface of the latent image carrier, the liquid colorant and possibly the surface of the intermediate carrier, as well as the surface roughness, i.e. the microscopic structure of the surface. Farther the regeneration station is used to set defined Process conditions with regard to the electrical properties on the surface of the latent image carrier, for example in terms of charge injection ratios and on the surface resistance. Accordingly, the Regeneration station fixes the surface energy, which is the wettability the surface with the liquid colorant controls. The regeneration station carries this to the surface of the image carrier, which is an intermediate carrier or a Can be a latent image carrier, a surface energy influencing substance, preferably surfactant solutions, especially non-ionic surfactants dissolved in water. This substance can, for example, with a layer thickness of less than 0.3 µm applied to the surface completely wetted, preferably in a time less than 5 ms.

Furthermore, the regeneration station can be a corona device contain a corona with an alternating voltage in the range of 1 to 20 kVss (measured from peak to Peak) at a frequency in the range of 1 to 10 kHz Has. This corona device can alternatively be applied the substance can be used or in combination with the substance.

In a further alternative, cleaning and Regeneration combined in a single operation. It for example, the pool cleaning or a Roller bath cleaning used. The cleaning liquid this becomes a substance that controls the surface energy, preferably a surfactant solution is added. With the Cleaning liquid will then apply this substance to the Transfer image carrier. Excess cleaning fluid can be removed again, such residues one Reprocessing can be fed.

Optionally, when cleaning with a cleaning liquid and an added substance that the surface energy controls, and after a regeneration drying the surface of the image carrier suitable means are carried out, for example by a warm one and dry air flow directed towards the surface is. This drying serves to make the surface active Increase shares and thereby increase their impact. It may also have a disruptive effect excess cleaning fluid avoided.

The following are photo-dielectric imaging processes explained with the help of latent images on a photoconductor can be generated by the liquid Coloring agent colored by overcoming the air gap can be. For this, the layer system of the Generates an image-wise distributed electric field, its components in space above the surface Force effect on charged particles, polarizable and exercise conductive objects, i.e. e.g. on polarizable Components of the colorant liquid. The electrical Field distribution on the surface of the photoconductor is at development using the transferring liquid Colorants made visible. Cleaning the top one Layer of photoconductor that is in contact with the colorant comes to the peculiarities of the liquid colorant be adjusted. In addition to cleaning this surface and the production of a defined state of charge upper insulating cover layer of the photoconductor must also the surface energy state of this top layer after each Dye transfer change restored or be preserved. The material of the upper insulating The top layer of the photoconductor must accordingly be used aqueous colorant. For coloring the surface of the photoconductor must have the surface energy ratios to be such that in those to be colored Latent image surfaces the carrier liquid with the Colorant sticks to the surface. At least it has to this liability condition for the solids content of the colorant be valid. In the areas not to be colored Surface of the photoconductor must have the electrical repulsion effect predominate so that no liquid in contact with the insulating surface of the photoconductor comes.

A variant is that because of the stability of the electric field over the insulating cover layer of the Photoconductor also a permanent introduction of the colorant containing liquid to this insulating layer can be made, the polarity of the fixed Colorant particles in the liquid should be such must have these particles through the electric field in the areas to be colored. Not in the Areas to be colored is the electrical field direction vice versa so that the charged solid colorant particles be repelled.

An imagewise coloring of the top layer of the photoconductor can also be achieved in that the to be colored Areas due to the combined effect of the surface energy relationship between the insulating cover layer and the liquid and electric field relative well and the areas not to be colored because of the reverse Field direction are relatively poorly wetted. This type of coloring or the combination with the deposit of the charged solid colorant particles especially for the development process at high speed. To a high speed process with a pure particle deposition without significant wetting differences between those to be colored and not Realize areas to be colored, the liquid layer very thin and the concentration of solid Colorant particles can be relatively high. The largest possible Particle charge is for high speed development advantageous.

With a conventional photoconductor with an external one photoconductive layer can be according to an embodiment this photoconductive layer with a thin insulating Be provided top layer. This top layer will chosen so that they meet the requirements placed on the Wettability and other surface properties, such as e.g. the charge injection property, for inclusion and delivering a liquid colorant.

FIGS. 21 to 26 show photo-dielectric imaging processes explained. Can be used for latent image generation a photo-dielectric process (Figures 21 and 22) is used in which the emergence of the latent image through an electrical field in the photoconductor is controlled. Farther can be a charging current controlled for latent image generation Process can be used (Figures 23 to 26).

An image generation process is explained with reference to FIG. which is also called Nakamura Process 1. The in the following photoconductor have each shown a lower conductive layer 110, a middle photosensitive Layer 112 and an upper insulating cover layer 114. This cover layer 114 determines the surface energy state, the electrical surface resistance and the charge injection properties of the photoconductor. The cover layer 114 itself influences the electrophotographic Process for generating the latent image is not essential.

In the image generation process according to FIG. 21, in one first step the layer system of the photoconductor first evenly charged with a polarity, being by Charge injections from the lower, conductive Layer 110 in the photoconductor layer 112 and / or through simultaneous even exposure (not shown) the creation of an electric field in the photoconductor layer 112 is prevented. Then that will Layer system with the opposite polarity reloaded, with an electric field in the photoconductor layer 112 arises (second step). In a third step the layer system is exposed imagewise, the latent image arises. FIG. 21 shows typical potential relationships entered.

FIG. 22 relates to a photo-dielectric imaging process, which is also called the Hall process. In one The first step is the layer system of the photoconductor evenly charged with a polarity, where both in the photoconductor layer 112 and in the Cover layer 114 builds up an electric field. Subsequently the layer system is exposed imagewise (second Step). In exposed areas, the electrical Field degraded in photoconductor layer 112 while it remains in unexposed areas. In one The third step is to recharge the battery evenly with the same polarity as in the first step. Subsequently there is an even surface exposure, in all areas of the photoconductor layer 112 electrical field is reduced and the latent image is formed (fourth step). 22 are typical again Potential relationships entered.

Figure 23 shows a photo-electric imaging process. also known as the Katsuragawa process, a charge current controlled for latent image generation Process is used. In a first step it will Layer system of the photoconductor initially with one polarity evenly charged, by charge injection from the lower conductive layer 110 into the photoconductor layer 112 and / or by simultaneous even exposure (not shown) the emergence of an electrical Field in the photoconductor layer 112 is prevented. In a second step, the layer system becomes visual exposed and at the same time with opposite polarity reloaded for charging in the first step, being in exposed Areas the emergence of an electric field is prevented in the photoconductor layer 112. In unexposed An electrical field is created in the areas Photoconductor layer 112. In a third step, this is Layer system evenly exposed, the latent image arises. Typical potential relationships are also shown in FIG entered.

Another charge current controlled imaging process is shown in FIG described, which is called the Canon NP process becomes. In a first step, the layer system of the photoconductor first with one polarity even charged, whereby by charge injection the lower conductive layer 110 into the photoconductor layer 112 and / or by simultaneous even exposure (not shown) the emergence of an electrical Field in the photoconductor layer 112 is prevented. The layer system is then exposed imagewise and at the same time, preferably using an AC corona, unload, the in exposed areas Creation of an electric field in the photoconductor layer 112 is prevented. In unexposed areas an electrical field is created in the photoconductor layer 112 (second step). In a third step this will be Layer system evenly exposed, the latent image arises. 24 shows typical potential relationships again entered.

FIG. 25 describes a charging current-controlled imaging process, which is called Nakamura Process 3. In a first step, the layer system becomes even charged with one polarity (in the example according to FIG. 25 the positive polarity was chosen) and at the same time exposed imagewise. This is done in exposed areas the creation of an electric field in the photoconductor layer 112 prevents while in unexposed areas both in the photoconductor layer 112 and in the Cover layer 114 creates a slightly smaller electric field. Then there is a second step uniform charge reversal with opposite polarity Charging in the first step. The surface potential is then in the first step exposed and unexposed Areas of the same size, in the example according to FIG. 25 approximately -500 Volt. In the final even exposure of the The entire layer system (third step) creates the latent image. Typical potential relationships are in again of Figure 25 entered.

FIG. 26 shows a charging current-controlled image generation process, which is called the Simac process. In the first The layer system becomes even with one step Polarity charged (positive in the example according to FIG. 26) and at the same time exposed imagewise. In exposed areas is the creation of an electric field prevented in the photoconductor layer 112 while in unexposed areas in both the photoconductor layer 112 and a somewhat smaller one in the cover layer 114 electric field arises. In the subsequent even The entire layer system is exposed in the second step the latent image, taking the electric field disappears in all areas of the photoconductor layer. Typical potential relationships are also shown in FIG entered.

LIST OF REFERENCE NUMBERS

10

final image

12

Photoconductor drum

P1, P2, P3

Direction sign

14

Intermediate carrier drum

16

Umladekorotron

18

exposure station

20

corotron

22

light source

24,24a

inking

26,26a

applicator

28

Heißlußfterzeuger

30

cleaning station

32

regeneration station

34

further cleaning station

35

Hot air station

36

feed

38

uniform liquid film

40

scoop roller

42

wells

44

scoop tank

46

doctor

48

droplet cover

50

droplet

52

doctor

54.56

line system

UB

bias potential

UP

potential pattern

60

surveys

62

surface sections

64

neckline

66

droplet

68

colorants

70

picture element

72

continuous layer of colorant

e

field strength

74

image location

76

topcoat

78

first areas of increased electrical conductivity

80

blank areas

84

wells

86

second areas of changed surface energy

88

third areas of microscopic surveys

90

metallic body

92

sublime islands

94

topcoat

100

tub

101

Residual ink

102

brush roll

103

brush

P4

rotation arrow

UR

tension

104

suction

106

bath

107

ultrasound source

110

conductive layer

112

photosensitive layer

114

topcoat

Claims (65)

1. Applicator element for providing a layer of liquid ink, in particular for inking a latent image carrier of a device for electrographic printing or copying,
   the surface of the applicator element (26) having a structure with a plurality of areas (78, 80, 86, 88), at which the detachment of droplets from the liquid layer is facilitated,
   this structure having a plurality of first areas (78) with increased electrical conductivity,
   and the structure of the surface of the applicator element having a plurality of second areas (86) having a surface energy that is varied with respect to the remaining surface (80),
   characterized in that the structure of the surface of the applicator element (26) has a plurality of third areas (88) that are formed as microscopic elevations on the otherwise smooth surface.
2. Applicator element according to claim 1, characterized in that the applicator element (26) comprises a material layer (76) having a medium surface energy, preferably between 30 and 50 mN/m with a low polar portion, preferably less than 10 mN/m, and in that the first areas (78) are generated by doping with foreign atoms, preferably metal atoms.
3. Applicator element according to claim 1 or 2, characterized in that DLC material is provided as a material layer.
4. Applicator element according to one of the preceding claims, characterized in that the second areas (86) differ from the remaining surface (80) in the polar portion and/or in the disperse portion of the surface energy.
5. Applicator element according to claim 4, characterized in that the applicator element (26) is coated with a first material layer (76), at the surface of which a plurality of cups (84) is formed, and in that the second areas (86) are formed by filling the cups (84) with a second material.
6. Applicator element according to claim 5, characterized in that ceramics is provided as a first material (76) and Teflon is provided as a second material.
7. Applicator element according to one of the claims 4 or 5, characterized in that DLC material, F-DLC material or SICON material is provided as a first material (76) and Teflon is provided as a second material.
8. Applicator element according to one of the preceding claims, characterized in that a Ni layer or a layer of Ni alloy, preferably CrNi, is provided as a first material (76) and Teflon is provided as a second material, the Teflon material being preferably embedded into the Ni layer in the form of pellets.
9. Applicator element according to one of the preceding claims, characterized in that the difference in height between the highest points of the microscopic elevations of the third areas (88) and the otherwise smooth surface amounts to 2 to 20 µm, preferably 5 to 10 µm.
10. Applicator element according to one of the preceding claims, characterized in that the first areas (78) and/or the second areas (86) and/or the third areas (88) repeat at a distance of 0.3 to 50 µm, preferably at a distance of 10 to 15 µm.
11. Applicator element according to one of the preceding claims, characterized in that the first areas (78) and/or the second areas (86) and/or the third areas (88) are arranged at regular distances or at stochastically distributed distances.
12. Applicator element according to one of the preceding claims, characterized in that with a regular arrangement of the first areas (78) and/or the second areas (86) and/or the third areas (88) the raster widths of these areas amount to 21.2 µm in order to correspond to the raster measure 1200 dpi.
13. Applicator element according to one of the preceding claims, characterized in that the change in material properties between the first areas (78) and/or the second areas (86) and/or the third areas (88) and the respectively remaining surface (80) takes place abruptly, preferably jump-wise.
14. Applicator element according to one of the preceding claims, characterized in that the change in material properties between the first areas (78) and/or the second areas (86) and/or the third areas (88) and the respectively remaining surface (80) takes place continuously, preferably without any distinctive jumps.
15. Applicator element according to one of the preceding claims, characterized in that the first areas (78) and/or the second areas (86) and/or the third areas (88), their distances to one another as well as their electrical conductivities, their surface energies or, respectively, their height with regard to the otherwise smooth surface are chosen such that droplets having a size of preferably 5 to 40 µm in diameter, in particular 10 to 20 µm in diameter, are formed.
16. Applicator element according to one of the preceding claims, characterized in that the first areas (78) and the third areas (88) are formed alternately.
17. Applicator element according to one of the preceding claims, characterized in that the local wave lengths of the first areas (78) and of the third areas (88) deviate from one another, the local wave length of the third areas (88) being at most one fifth of the local wave length of the first areas (78).
18. Applicator element according to one of the preceding claims, characterized in that the second areas (86) and the third areas (88) are combined with one another.
19. Applicator element according to claim 18, characterized in that the second areas (86) and the third areas (88) are formed alternately.
20. Applicator element according to one of the claims 18 to 19, characterized in that the local wave lengths of the second areas (86) and of the third areas (88) are different from one another, and in that the local wave length of the third areas (88) corresponds to one fifth of the local wave length of the second areas (86) at a maximum.
21. Applicator element according to one of the preceding claims, characterized in that the roller-shaped applicator element has a metallic cylindrical basic body (90), to which a cover layer (76) having a reduced conductivity and a medium surface energy, preferably in the range of 30 to 50 mN/m with a polar portion of > 5 mN/m, preferably made of the material ceramics, is applied, in that this cover layer (76) has a regular cup structure with a resolution of 1200 dpi, in that the cups (84) are filled with a material, preferably Teflon, that has a lower surface energy and a lower conductivity than the material of the cover layer (76).
22. Applicator element according to claim 21, characterized in that the surface of the filled cups (84) covers a portion of 60 to 90 %, preferably of 70 to 80 % of the generated surface of the cover layer (76).
23. Applicator element according to one of the preceding claims, characterized in that the thickness of the cover layer (76) lies in the range of 1 to 500 µm.
24. Applicator element according to one of the claims 21 to 23, characterized in that the cups (84) are not completely filled with the second material so that there results a surface with elevated islands (92).
25. Applicator element according to one of the claims 21 to 24, characterized in that the cups (84) are stochastically distributed and have a distance from one another that lies in the range of 0.3 to 50 µm, preferably in the range of 0.3 to 20 µm, and in that the cups (84) are only partly filled with the second material so that elevations (96) of the cups (84) remain free from this second material.
26. Applicator element according to one of the preceding claims, characterized in that it is arranged in an inking station,
    a latent image carrier (12) having a potential pattern (UP) corresponding to an image pattern to be printed being arranged opposite the applicator element (26, 26a),
    an air gap (L) being provided between liquid layer (48, 72) and the surface of the latent image carrier (12) that is opposed thereto,
    and, for inking the latent image on the latent image carrier (12), droplets (50) being transferred from the liquid layer (48, 72) onto the surface of the latent image carrier (12) by overcoming the air gap (L).
27. Applicator element according to one of the preceding claims, characterized in that the applicator element (26, 26a) is roller-shaped.
28. Applicator element according to one of the preceding claims 26 to 27, characterized in that the liquid layer (48) is formed as a layer having a plurality of droplets.
29. Applicator element according to one of the preceding claims 26 to 28, characterized in that the air gap (L) between the applicator element (26) and the latent image carrier (12) lies in the range of 50 to 1000 µm, preferably in the range of 100 to 200 µm.
30. Applicator element according to one of the preceding claims 26 to 29, characterized in that a bias potential (UB) in the form of a direct voltage is applied to the applicator element (26).
31. Applicator element according to claim 30, characterized in that an alternating voltage having a frequency of preferably ≥ 5 kHz is superimposed on the direct voltage (UB).
32. Applicator element according to one of the preceding claims 26 or 27, characterized in that the surface of the applicator element (26) is provided with a continuous liquid layer (72).
33. Applicator element according to claim 32, characterized in that the thickness of the continuous liquid layer (72) lies in the range of 5 to 50 µm, preferably at approximately 15 µm.
34. Applicator element according to one of the preceding claims 26 to 33, characterized in that the liquid ink and/or the liquid layer contains a nontoxic and/or nonflammable and/or non-odorous carrier liquid, preferably water.
35. Applicator element according to claim 34, characterized in that the carrier liquid contains colour particles, fillers, surface tension-influencing additives, viscosity controlling additives, fixing adhesives and/or ultraviolet hardening polymers.
36. Applicator element according to one of the claims 34 to 35, characterized in that the solid matter content in the carrier liquid amounts to ≥ 20 %.
37. Applicator element Device according to one of the preceding claims 26 to 36, characterized in that the liquid film is supplied to the surface of the applicator element (26, 26a) via a feed roller (36).
38. Applicator element according to claim 37, characterized in that the feed roller (36) is rotated in the same direction or in the opposite direction with respect to the motion of the applicator element (26, 26a).
39. Applicator element according to one of the claims 37 or 38, characterized in that a liquid film (38) is supplied to the feed roller (36) via a scoop roller (40), a portion of which is dipped into a supply of liquid ink.
40. Applicator element according to claim 39, characterized in that the scoop roller (40) is, on its surface, provided with a cup raster (42), and in that a doctor blade (46) acts on the surface of the scoop roller (40) so that only the liquid volume that is present in the cups (42) of the scoop roller (40) is conveyed.
41. Applicator element according to claim 40, characterized in that the scoop roller (40) is designed as an anilox roller having a chamber doctor blade.
42. Applicator element according to one of the preceding claims 37 to 41, characterized in that a smooth liquid film is sprayed onto the feed roller.
43. Applicator element according to one of the preceding claims 26 to 36, characterized in that the applicator element dips with a portion thereof into a bath containing the ink, and in that the dosage of the accepted amount of liquid takes place via an elastic roll doctor that acts on the surface of the applicator roller.
44. Applicator element according to one of the preceding claims 26 to 43, characterized in that the inked image on the latent image carrier is treated such that at least a part of the carrier liquid escapes, preferably evaporates.
45. Applicator element according to claim 44, characterized in that a hot air stream is applied to the inked image for the escape of the carrier liquid.
46. Applicator element according to one of the preceding claims 26 to 45, characterized in that an alternating force field is present in the air gap (L), said force field acting on the liquid layer (48, 72) or the surface of the applicator element.
47. Applicator element according to claim 46, characterized in that an alternating electric field and/or an alternating magnetic field and/or an alternating acoustic field, in particular an ultrasonic field, is used as an alternating force field.
48. Applicator element according to one of the preceding claims 1 to 47, characterized in that the liquid layer to be applied to the surface of the applicator element has a relatively low surface tension in the range of 20 to 45 mN/m, in particular in the range of 25 to 35 mN/m.
49. Applicator element according to claim 48, characterized in that the liquid layer has a relatively low viscosity in the range of 0.8 to 50 mPa·s, in particular in the range of 3 to 30 mPa·s.
50. Applicator element according to one of the preceding claims, characterized in that the liquid layer has a relatively high surface tension in the range of 50 to 80 mN/m, in particular in the range of 55 to 70 mN/m.
51. Applicator element according to claim 50, characterized in that the liquid layer has a viscosity in the range of 0.8 to 300 mPa·s.
52. Applicator element according to one of the preceding claims 26 to 51, characterized in that the air gap (L) has a gap width depending on the printing resolution (dpi).
53. Applicator element according to claim 52, characterized in that the gap width amounts to two times to twenty times the distance of the picture elements at a predetermined print resolution, in particular five times to ten times the distance.
54. Method for providing a layer of liquid ink, in particular for inking a latent image carrier in a device for electrographic printing or copying,
    the surface of the applicator element (26) being prepared such that it has a structure with a plurality of areas (78, 80, 86, 88), at which the detachment of droplets from an applied liquid layer is facilitated,
    this structure having a plurality of first areas (78) with increased electrical conductivity,
    and the structure of the surface of the applicator element having a plurality of second areas (86) having a surface energy that is varied with respect to the remaining surface (80),
    characterized in that the structure of the surface of the applicator element (26) has a plurality of third areas (88) that are formed as microscopic elevations on the otherwise smooth surface.
55. Method according to claim 54, characterized in that the liquid ink and/or the liquid layer contains a nontoxic and/or nonflammable and/or non-odorous carrier liquid, preferably water.
56. Method according to claim 55, characterized in that the carrier liquid contains colour particles, fillers, surface tension-influencing additives, viscosity controlling additives, fixing adhesives and/or ultraviolet hardening polymers.
57. Method according to one of the claims 55 or 56, characterized in that the solid matter content in the carrier liquid amounts to ≥ 20 %.
58. Method according to one of the preceding claims, characterized in that the liquid film is supplied to the surface of the applicator element (26, 26a) via a feed roller (36).
59. Method according to one of the preceding claims, characterized in that the liquid layer (48) is formed as a layer having a plurality of droplets.
60. Method according to one of the preceding claims, characterized in that the surface of the applicator element (26) is provided with a continuous liquid layer (72).
61. Method according to claim 60, characterized in that the thickness of the continuous liquid layer (72) lies in the range of 5 to 50 µm, preferably at approximately 15 µm.
62. Method according to one of the preceding claims, characterized in that the liquid layer has a relatively low surface tension in the range of 20 to 45 mN/m, in particular in the range of 25 to 35 mN/m.
63. Method according to claim 62, characterized in that the liquid layer has a relatively low viscosity in the range of 0.8 to 50 mPa·s, in particular in the range of 3 to 30 mPa·s.
64. Method according to one of the preceding claims 54 to 61, characterized in that the liquid layer has a relatively high surface tension in the range of 50 to 80 mN/m, in particular in the range of 55 to 70 mN/m.
65. Method according to claim 64, characterized in that the liquid layer has a viscosity in the range of 0.8 to 300 mPa·s.

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