EP0978388A2 - Device for drying print - Google Patents

Abstract

The printing paper (28) is fed across a printer head (36) and passes a sensor (38) that responds to the printed information. The sensor output is used by a controller (34) and this directs the action and movement of a heat source (40) to dry the damp printed information. The source is in the form of a laser.

Description

The present invention relates to a device for Drying of printing ink or ink according to the generic term of Claim 1 and a drying process that a Printing process of applying the printing ink a suitably designed printing unit is connected downstream and fixed the printed image by drying these media.

It is known from the prior art to print images of Printing units, in particular those using electronic Control are generated by a generic Drying device to dry so that the printed image without Danger of blurring or getting lost is fixed and one User is available for subsequent use. So it is particularly common to apply liquid printing inks or inks, for example by means of electronic inkjet printing processes, after the actual printing process to dry by additional heat (over the anyway existing ambient heat), so the period between the actual printing and the fixation of the Print image remains short.

Such a drying process traditionally takes place as downstream step of the printing process using heated Rolls over which the printed image carrier in the form of Paper, foil or the like out, or it will be over large format Radiant heaters applied heat radiation. The drying speed that can be achieved (and thus the overall printing speed such an installation) limited due to the dimensioning and design of the Heat source, and in particular its ability within a short amount of heat to the print image carrier bring. However, this leads to numerous practical ones Difficulties, as will be explained below.

Fig. 9 illustrates in the schematic sectional view a generic device from the prior art. A printed image carrier 10, in the present case a paper sheet, is with a selectively applied printed image 12 (Printing, for example, using an inkjet process) provided, for drying the printed image with full line of infrared emitted by an infrared radiator 14 or heat radiation 16 is applied.

The line-shaped drying of Fig. 1 - in the form of a Line extends transversely to the feed direction of the print image carrier the continuous heat radiator - enables an acceleration of the process, e.g. by higher Drying temperatures with which the print image carrier acts becomes. However, as in the case of traditional ones Heating, for example, by a heated one Transport role, however, introduces a related to that Carrier material high energy input to embrittlement the applied layer of paint and beyond to one uncontrollable influence on the moisture content of the carrier material, e.g. Paper, so when subsequent folding or bending the known Drying process results in very substantial process engineering Cause problems.

10 and 11 illustrate the example of a point unprinted carrier paper (Fig. 10) or a printed one Place (Fig. 11), as is, depending on the irradiation time, temperature and vapor pressure on or in Develop carriers. In each of the figures, the reference symbol is shown 18 the temperature profile and the reference number 20 the vapor pressure curve on or in the printed image carrier 10 and in Print image 12. The energy input takes place in the direction of arrow 22 using full-line (broad) infrared radiation; the Arrow 24 shows (arrow size proportional to the respective Energy) the absorption in the carrier or in the printed image. Only a very small amount of energy (arrow 26) is from Carrier transmits and occurs at the opposite of the radiation Page again.

According to this relatively high absorption of the registered, high thermal energy is the temperature rise 18 over the time high, so that embrittlement or unwanted, oversized drying effects - recognizable even in the strong falling vapor pressure curve 20 - with correspondingly negative Effects on quality and processability of the end product are the result.

In addition to the described adverse effects the conventional procedure for drying printed images Disadvantage on that for certain print image carriers, for example Thermal paper, other thermosensitive materials, or else certain carrier foils, not or only with great restrictions is suitable: that would be a full line (due to continuous feed therefore full area) Heat input with so-called thermal paper (with a paper reacted to the influence of heat, which in a heated place with a blackening or the like. reacts) over the entire area to react to the heat input and so a differentiation to a usable print image no longer make possible. In addition comes with the described State of the art method of basic Disadvantage that a whole area, high heat or temperature input with correspondingly high energy and therefore Cost is connected.

The object of the present invention is therefore a generic Device for drying printing ink or Develop ink to make both shorter Drying times, so higher printing speeds with continuous operation, can be made possible without the print carrier being adversely affected. Also are intended to be energy efficient and universal for a wide variety of Print image carriers, including thermosensitive print image carriers, be significantly increased or broadened.

The task is accomplished by the device with the features of claim 1 and the method according to the claim 14 solved.

This is because, in contrast to State of the art, through the invention a print image dependent Drying process in the form of a specific blackening selective or color application of the printed image Heating with a point heat source. So that will largely the heat input, optimized for each Printing ink or ink, limited to the actual printed area, while those large, unprinted Paper surfaces used in conventional heating methods dehydrated due to - unnecessary - heating were unaffected by the procedure according to the invention stay and their advantageous material properties completely preserved.

Because the heat input is limited to the pure printed area is, on the one hand, a potentially faster carrier or sheet feed possible because only those to be dried Color ranges with a permissible maximum Heat radiation can be applied, and also increased the energy efficiency of such a printing device considerable, since no unprinted areas (unnecessary) be heated.

It is within the scope of the present invention as "Pressure device" means any device that is suitable is one that requires subsequent heat drying Apply printing ink to a print carrier; next to the Inkjet printers mentioned by way of example belong to this for example also pen plotters, thermal transfer printers or the like. Devices.

As far as in the context of the invention, the heat source is a point Emits beam, is as "punctiform" anything understand the image of the beam generated by the print image carrier, which is small compared to the printed image carrier and usually around a minimum line width of one is adapted to the respective printed image, but also smaller or can be bigger. In this respect, such devices are also encompassed by the invention, in which a Printing lying, unprinted carrier areas from one applied, controlled heat radiation.

Finally, as an "infrared component" within the scope of the invention to understand such radiation, at least partially one for drying one applied at a time Color or ink suitable heat radiation in their spectrum contains.

Advantageous developments of the invention are in the Subclaims described.

So in principle it is possible to use the electronic position control signal for the tracking or Positioning of the documents intended for drying depending on the print image Generate heat source in two ways: First is it provided an approximately optical scanner for this purpose to use with associated sensors, which is the printed one Scans image and based on the captured print image, according to the detected darkness, generated the data for positioning the heat beam. Such a device is particularly suitable as an additional unit for existing printing devices that no or only cumbersome direct access offer the print data.

In contrast, it is an alternative embodiment in the frame the invention also possible by a control unit for the printing device, such as a computer, generates a printed image to be evaluated directly as an electronic data signal and the print image data based on their position the printed image carrier the surface sections to be heated (Points) correspond directly to corresponding position data the heat source positioning device. In particular, page-oriented printer languages, such as Postscript, PDF, HTML or the like should be a good basis for this offer, so that when such, readout unit provided in accordance with further training which at Scanning device described in the aforementioned embodiment can be omitted.

It is also within the scope of the invention by suitable control the pulsed heat source to set it up so that an average surface temperature of about 60 ° C is not exceeded. By keeping this limit namely, it has been shown that common carrier materials, in particular Papers, not detrimental to the drying process to be influenced.

It is also within the scope of the invention that the drying effect triggering infrared radiation with regard to performance, Setting the radiation spectrum and pulse frequency so that depending on a particular ink or ink, here an optimum drying is achieved. So in particular a pulsed radiation with a pulse frequency <20 KHz with energy output <2 watts as particularly suitable for conventional Proven inkjet printer.

It is also within the scope of the invention as a heat radiator use different illuminants or spot types: In addition to pure infrared radiators, in particular Lamps are used which - for the purpose of improved Adjustment or setup - also spectral components in the have visible area. Such lights can then with suitable focus means, for example one Concave mirror and / or optical lens unit, for pinpoint accuracy Generation of heat radiation can be provided. Alternatively it is possible to be one - especially as a heat radiator easily controllable and precisely positionable - laser to use, the type and performance selected depending on the task becomes. A laser in particular offers the advantage of one extremely responsive control and focus speed, so there is practically no delay due to each Alignment of the lamps is done. Alternatively it is possible, a so-called high-power flash lamp as a radiation source to use, or again a full line Spotlight consisting of a plurality of arranged side by side Single radiators, which are only selective and can be controlled depending on a print image. A such an arrangement increases the drying speed that can be achieved further.

The present invention is advantageously suitable for use with a variety of possible image carriers. Next Common paper, coated or uncoated, is therefore in particular also thermal paper can be used; add cardboard boxes, Plastics, plastic films, textile substrates or the like.

As a result, the device according to the invention and the inventive method for drying printing ink or ink achieves that - in contrast to the known State of the art - the energy input to the concrete Print image is limited and so with regard to necessary Energy consumption as well as undesirable burden on the unprinted carrier areas are optimized.

Fig. 1:

ein schematisches Blockschaltbild mit dem Zusammenwirken verschiedener Funktionskomponenten der erfindungsgemäßen Vorrichtung zum Trocknen von Druckfarbe;

Fig. 2:

ein Verfahrensablaufdiagramm, welches das Zusammenwirken mit den Funktionseinheiten gemäß Fig. 1 zeigt;

Fig. 3:

ein Pfeildiagramm, welches näher im Detail die physikalischen Abläufe bei einem Wärmestrahlungseintrag in einen bedruckten Druckbildträger verdeutlicht;

Fig. 4:

eine alternative Darstellung der beim Strahlungseintrag auftretenden Vorgänge;

Fig. 5, Fig. 6:

Energieeintrag, Absorption und Transmission mit Temperatur- und Dampfdruckverlauf über der Zeit bei unbedrucktem (Fig. 5) bzw. bedrucktem (Fig. 6) Druckbildträger;

Fig. 7:

eine schematische Schnittansicht durch eine Wärmequelle gemäß einer ersten Ausführungsform mit optischer Fokkusierungseinheit;

Fig. 8

: eine schematische Seitenansicht einer Lasereinheit als alternativer Wärmequelle;

Fig. 9:

eine schematische Seitenansicht einer Trocknungsvorrichtung aus den Stand der Technik und

Fig. 10, Fig. 11:

Energiefluß-, Temperatur- bzw. Dampfdruckdiagramme analog Fig. 5, Fig. 6 bei einer Vorrichtung aus dem Stand der Technik.

Further advantages, features and details of the invention result from the following description of exemplary embodiments and with reference to the drawings; these show in

Fig. 1:

a schematic block diagram with the interaction of various functional components of the inventive device for drying printing ink;

Fig. 2:

a process flow diagram showing the interaction with the functional units of FIG. 1;

Fig. 3:

an arrow diagram which illustrates in more detail the physical processes involved in the entry of heat radiation into a printed printed image carrier;

Fig. 4:

an alternative representation of the processes occurring during the radiation input;

Fig. 5, Fig. 6:

Energy input, absorption and transmission with temperature and vapor pressure curve over time with unprinted (FIG. 5) or printed (FIG. 6) print image carrier;

Fig. 7:

a schematic sectional view through a heat source according to a first embodiment with optical focusing unit;

Fig. 8

: a schematic side view of a laser unit as an alternative heat source;

Fig. 9:

is a schematic side view of a drying device from the prior art and

10, 11:

Energy flow, temperature and vapor pressure diagrams analogous to FIGS. 5 and 6 in a device from the prior art.

A paper print image carrier 28, as in FIG. 1 shown in the schematic side view, of one not Feed unit 30 shown in more detail in the feed direction led along arrow 32. With the print carrier 28 can either be a continuous, Endless bearer, or a sheet which is guided in the direction of arrow 32.

Controlled by a suitably trained control unit 34, such as a PC, otherwise designs a printhead 36 known and not shown printing device the printed image on the paper support 28 according to the electronic Control signals from the computer. Schematic through that Shown at 38, a sensor receives one, for example line-by-line scanner the print image and in turn converts this into corresponding signals; such scanner heads or scanner strips are as such also known from the prior art and react usually on the different light reflection from unprinted or printed areas. In response to that scanned printed image patterns by the unit 38 thereupon becomes a control signal in the control unit 34 for a movable or transverse to the feed direction 32 directable heat source 40, in the present case by realizes a pulsed laser, generates, and synchronized to Printing by printhead 36, only delayed by that Runtime between printhead and heat source 40, this runs the print image in an energy and temperature optimized manner to selectively only the printed, still moist Apply heat to surfaces to dry them.

The process flow diagram in FIG. 2 illustrates the sequence of steps: In step S1, unprinted paper fed, printed in step S2. Printing takes place by control by means of control unit 34. In step S3 the printed carrier is scanned by means of a sensor unit 38; whose sensor signal is on the control unit 34 at. The control unit 34 then activates the positionable Heat source 40, whereupon this in step S4 selectively and depending on the print image heated the print carrier, to make the print image more energy-efficient and time-optimized dry. In step S5, the dried print carrier moves from the plant.

Before with reference to FIGS. 5 and 6 - analogous to the illustration to the prior art according to FIGS. 11 and 12 - explained should be how energetically and absorption technically the procedure according to the invention has an advantageous effect, is intended to continue with reference to FIGS. 3 and 4 be described in detail what physical processes when energy input by infrared radiation in the printed or unprinted paper.

Arrow 42 in Fig. 3 shows the energy impulse that with the the printed sheet 12 provided carrier sheet 10 applied becomes. While arrow 44 reflected that from the printing Clarifies energy, arrow 46 shows the reflection from the unprinted paper surface. Absorption in the printing ink takes place by means of arrow 48, in the unprinted Area by means of arrow 50. In the carrier material 10 comes it then leads to capillary or chemical influences; Heat conduction also takes place along arrows 52. Transmitted energy passes along arrows 54 (through Carrier plus printing) or 56 (carrier only) while Arrow 58 shows the vapor pressure.

Analogously, arrows 60 and 62 show the pulse-shaped in FIG Energy input in the printing (60) or in the unprinted Paper surface (62) with associated absorption 64 or 66. Reflected energy is indicated by the reference numerals 68 displayed while the transmitted energy signal 70 on the opposite side of the entry point from the Carrier material emerges.

Will now, as shown in FIGS. 5 and 6 and as based on 1 and 2, only in the area of Printing 12 a punctual, strong, impulsive Energy input while the remaining, unprinted carriers practically not (or only with low reflection energy) is applied, so 5 shows the case of a non-printed surface, that very little energy reflects, transmits and is absorbed (symbolized by size the arrows used); the temperature curve shows accordingly 18 or the vapor pressure curve 20 one compared to State of the art favorable development. As shown in Fig. 6 In addition, temperature and vapor pressure only develop selectively in the area of the printed to be dried Surface 12, so that here the beneficial drying effect is achieved while the unprinted area is practical remains unaffected.

7 and 8 show two possible embodiments for the heat source 40 according to FIGS. 1/2 Incandescent lamp unit 72 as a central illuminant a tungsten filament 74, the concave mirror in the center of one 76 is arranged and an upstream Pulse generator 78 acted on with pulse-shaped control signals becomes. 7 with schematically drawn Radiation path shows the radiation of the incandescent lamp unit 72, partly in the optically visible, partly in Infrared lies, punctiform on the one with printing 12 provided section focused on the carrier 10.

Alternatively, the arrangement according to FIG. 8 sees one in pulse operation operable laser 80, which is an i.w. parallel, emitted beam 82 with infrared portion focused on the printed section 12 at a point.

The respective positioning units are not shown - either mechanical or electronic - the units 7 and 8 on respective punctiform sections of the Align the printed image.

According to an advantageous development of this invention, it is it is also possible not only to use a single, to implement a spotlight unit, but rather these from a plurality of along to design a row of arranged units. Through selective Control individual elements of this line accordingly one to be dried underneath The positioning effort could then be reduced and potentially the drying rate can be increased further.

While in the exemplary embodiment of FIG. 1 described above and 2 the print image to be dried by means of an additional Scan or scanning unit was captured to the corresponding To generate control signal for the heat radiator, so it is in the context of an alternative embodiment of the invention also possible to control this signal directly by appropriate Evaluations or calculations of the anyway for printing by the printhead is usually available to obtain a standing print image. So included modern printer or image / text output languages such as Postscript, PDF or HTML specific positioning instructions for the printhead, which, to correct appropriate parameters, also used directly to control the heat source can be.

It is also within the scope of the invention to have a variable feed rate a relative movement between the heat source and to provide printed image carriers, depending on how high a current print image density (and thus a number of points to be dried).

Claims (14)

Device for drying printing ink or ink, which was applied as a printed image (12) of a printing device (36) on a printed image carrier (10, 28), characterized by a print image detection device (38) which is designed to detect image positions of the print image formed by the printing ink or ink on the print image carrier and to output associated electronic position control signals, a heat source (40) which can be operated in a pulsed manner and which is designed to generate a point-shaped beam with an infrared component directed onto the print image carrier, and a control and positioning device (34) which is assigned to the heat source and which, in response to the position control signal, tracks the infrared beam (82) to the image positions of the printed image in such a way that a print-dependent drying process of the printing ink or ink is carried out. Device according to claim 1, characterized in that a drying operation by the control and position device is set so that a medium Surface temperature of the print image carrier <80 °, and preferably <60 °. Device according to claim 1 or 2, characterized in that that the print image capture device has a scanning device (38) which is and / or scanning the print image carrier line by line generates the electronic position control signals. Device according to claim 1 or 2, characterized in that that the print image capture device has a readout unit with one of the printing device assigned data processing system is connected and based on that of the data processing system generated print image data for the Print image device the electronic position control signals for the control and positioning device generated. Device according to one of claims 1 to 4, characterized characterized that a wavelength of the punctiform Beam between 1,000 and 5,000 nm, preferred is between 1,600 and 3,000 nm. Device according to one of claims 1 to 5, characterized characterized that a pulse frequency of the pulse-shaped Beam in the range between 5 and 20 kHz, preferred between 10 and 15 kHz. Device according to one of claims 1 to 6, characterized characterized that a radiation power of the point beam in the range between 0.2 and 2 Watts, preferably between 0.5 and 1.5 watts. Device according to one of claims 1 to 7, characterized characterized in that the printed image carrier relative to the printing device and the heat source with a preferred variable speed between 1.0 and 10 m / s, preferably between 1.5 and 7.5 m / s, is moved. Device according to one of claims 1 to 8, characterized characterized that the heat source is a lamp with radiation components in the visible wavelength range having. Apparatus according to claim 9, characterized in that the illuminant with a focus device is provided for generating the point beam. Device according to one of claims 1 to 10, characterized characterized that the heat source is a high power flash lamp having. Device according to one of claims 1 to 8, characterized characterized in that the heat source is a pulsed operable Has laser source. Device according to one of claims 1 to 12, characterized characterized that the printed image carrier from the Group is selected from coated or uncoated Paper, thermal paper, cardboard, plastic film, other plastic carriers, textiles. Method for drying printing ink or ink which has been applied as a printed image of a printing device on a printing image carrier, in particular for operating a device according to one of claims 1 to 12, characterized by the steps: Capturing the print image and generating associated electronic position control signals, Controlling a heat source that can be operated in a pulsed manner and generates a punctiform infrared beam with the electronic position control signals in such a way that the heat source tracks the printed image and selectively carries out drying in the area of the printed image.

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