WO1988007450A1

WO1988007450A1 - Device for laser transfer printing

Info

Publication number: WO1988007450A1
Application number: PCT/DE1988/000185
Authority: WO
Inventors: Peter Kleinschmidt; Gerhard Mader; Hans Meixner
Original assignee: Siemens Aktiengesellschaft
Priority date: 1987-03-27
Filing date: 1988-03-23
Publication date: 1988-10-06
Also published as: ATE76609T1; DE3871520D1; EP0338025A1; DE3710183A1; EP0338025B1; JPH02502708A

Abstract

Laser transfer printing, in particular multicolour printing, for which an inking ribbon coated with microcapsules (41) containing the relevant printing ink is used.

Description

Device for laser transfer printing

From GB-A-2 173 452 an apparatus and a method for laser printing is known. A print carrier, e.g. a sheet of paper, the surface of the paper being coated directly with microcapsules, initially over the entire surface. These microcapsules contain an ink used as printing ink. According to a variant, as soon as such a microcapsule is hit by the radiation from a laser, this capsule is broken open, namely if the incident laser radiation has a certain minimum energy. It can be provided that the ink contained in the capsule is absorbent for this laser radiation in such a way that the laser beam energy is absorbed by this ink. An alternative is that the material of the wall of the capsule has such laser radiation absorption. It has also already been stated to use such material for the wall of the capsule that such a chemical reaction takes place when the laser radiation strikes that the capsules can be broken open with a minimum of radiation energy.

The printing process can be carried out without the use of printed letter masks in such a way that the individual letters are put together point by point by the appropriately controlled focused laser beam.

This publication describes a further variant according to which, in accordance with the negative of the print pattern, microcapsules hit by the laser radiation can be made conductive and can thus be detached from the originally all-over coating. The sheet of paper is then placed in a mechanical crimping device with the coating of its surface corresponding to the positive of the print pattern with microcapsules directed where the transfer of the printing ink takes place with the bursting of the microcapsules.

The above-mentioned document also indicates the possibility of multi-color printing. For this purpose, microcapsules are filled with ink in a variety of colors, e.g. are distributed microcapsules with red ink contained therein and those with green ink contained therein. Laser radiation with different wavelengths is used and microcapsules are provided which, depending on the color they contain, respond selectively to a respective wavelength of the laser radiation.

In US-A-3,351,948 for multi-color printing with microcapsules it is provided that the microcapsules of the different colors, each color individually, are arranged in rows. The respective line is then actuated with the laser radiation for printing in the respective color.

The use of an ink ribbon for transfer printing has been known for a long time from US Pat. No. 3,570,380. The print medium, e.g. Paper and this ink ribbon are brought into surface contact with one another at least in the intended printing area. Intensity hitting the ink ribbon causes the printing dye contained in the ink ribbon to be transferred to the printing medium. This ribbon can be used for single color printing. Ribbons have also been used in devices described in more recent publications. For a thermal transfer printer (3P-A-58-110 270) the use of multicolored ink ribbon has already been provided, as is known from conventional typewriters, in which ink ribbons with parallel stripes of different color, e.g. black and red.

Extensive further prior art, such as the European laid-open publication 0 205 083 and the Japanese publication JP-A2-61-1958888, describes a method in which light is applied to a microcapsule occupied ribbon of microcapsules hit by the radiation undergo a physical change. In the device in question, the ink ribbon, on which irradiated and non-irradiated microcapsules are now located, continues to a place where the layer of the microcapsules on this ink ribbon is brought into contact with a printing medium. During the close contact of the microcapsules with the print carrier, either only the irradiated or only the unirradiated microcapsules are transferred to the print carrier (and the other microcapsules remain on the ink ribbon). Microcapsules are now present on the print carrier in such a distribution as it corresponds to the previous irradiation of the ink ribbon or how this corresponds to the pattern to be printed. With the irradiation, therefore, a merely latent image is generated on the ink ribbon, this latent image is transferred to the print carrier when it comes into contact with the printing medium, and the latent image is only later converted into the actual image on the other in some other device, in particular a mechanical squeezing device Print media converted. These known methods thus perform printing using several types of energy, for example radiation energy for generating the latent image and mechanical pressure for actually printing the latent image on the printing medium.

Furthermore, methods are known by means of which characters can be printed on a print carrier using an ink ribbon. By appropriately pressing the ink ribbon onto the print carrier, using a specific pressure and temperature, dye is transferred from the ink ribbon onto the print carrier. Here too, laser radiation is used to generate the necessary temperature, namely in its property as thermal radiation. A "transparency" of the ink ribbon with respect to such laser radiation is not necessary since the thermal effect of the laser radiation easily passes through the ink ribbon.

The object of the present invention is to implement such measures or to specify such a device for laser transfer printing, which works with a print carrier which is not necessarily specially prepared, for example with normal paper, which enables high printing speed and which ensures high registration accuracy for multicolor printing. The invention is intended to make it unnecessary to have to carry out a subsequent treatment (removal of printing ink not used for printing).

This object is achieved by means of a device for laser transfer printing with at least one laser beam source for the generators (each) of a focused laser beam, with an electrical control device for this beam source and its laser beam, with a receptacle for a print carrier, e.g. Paper in sheet or roll form, with a receptacle for an ink ribbon, which serves as a carrier for at least one printing dye, with a pressure device between which the ink ribbon and the printing medium are pressed together, this device permeable to the respective laser beam Has dissolved, and this ribbon is a carrier film that is coated with microcapsules, the carrier film being transparent to the one or more laser wavelengths used. The microcapsules contain the printing dye. In the case of multicolor printing, there are microcapsules filled with differently colored printing dye, which are distributed over the surface of the carrier film of the ribbon. The distribution can be random or patterned. For example, the latter can be a line pattern.

With such a device, printing can be carried out, in which multi-color printing can also be carried out in a single pass. This not only has the advantage that a high printing speed can be achieved, but also the coverage of the individual color images is not dependent on repeated adjustment or positioning of the printing medium and the laser beam control.

The micro- In addition to the dye (of the respective color), capsules can also contain an absorber material which contributes to the fact that focused laser radiation which is directed toward a particular microcapsule, even at a relatively low intensity, causes this microcapsule to be broken open for the purpose of pressing is burst or the like. Additionally or alternatively, it can also be provided that the wall of the microcapsule consists of such a material that has an absorber effect for the laser radiation.

In addition to the printing dye, the microcapsules can contain a chemically reactive substance which, in the radiation provided, enables a reaction which releases more energy than was absorbed in the reactive substance by radiation energy. It can be provided that this process is wavelength-dependent.

For multi-color printing, it can advantageously be provided that laser radiation sources with different wavelengths are used and those absorber materials are used which selectively respond to one of the respective wavelengths. A specific printing ink can then be controlled with the radiation of a specific laser wavelength, the associated microcapsules of which are burst. It is then printed in this color at the respective location. In this way, several colors can be selectively printed practically in the same place at the same time, with the result that the printing point has the corresponding mixed color.

Laser diodes are particularly suitable for realizing the invention as a laser beam source. Ga-As laser diodes with a wavelength of 0.81 μm and InGaAsP laser diodes with a wavelength of 1.3 and 1.6 μm are available.

Provision can also be made for the ink ribbon to be coated with microcapsules of one color each arranged in dense rows. For multicolor printing it is then necessary to print the respective color line for the respective color to hit on the ribbon.

FIG. 1 shows a simple device for preferably single-color printing. With 1 the print carrier, e.g. Paper, designated. 2 denotes a piece of the ink ribbon used according to the invention with a carrier film 3 and the layer 4 thereon with microcapsules. This layer 4 with the microcapsules faces the printing surface of the printing medium 1. The pressure device consists of a body 5 transparent to the laser radiation to be described below and a counter surface 6 e.g. a roller.

7 denotes a laser diode array. It is sufficient if this array is a linear arrangement of laser diodes. 8 is a condenser and 9 an imaging lens. The rays of the peripheral laser diodes of this array are shown in the figure at 10 and 11. The electrical control is designated by 12. Depending on which of the laser diodes of the array is controlled, a respective narrowly delimited area (dot) in the layer 4 of the microcapsules is irradiated. The absorption of the laser radiation striking the microcapsules in question leads to the destruction of the microcapsules and to the release and transfer of the printing dye contained in these microcapsules onto the surface of the print carrier.

Figure 2 shows an embodiment of a device according to the invention, which is specially designed for multicolor printing. The print medium, e.g. Paper, again labeled 1. The ink ribbon is designated 2 and touches the paper at least at location P of the printing process to be carried out at the moment. The layer containing the microcapsules 41 on the carrier film 3 is again designated by 4. For multi-color printing, the microcapsules 41 each contain printing fluid of different colors. The different colored microcapsules are e.g. mixed closely distributed.

5 denotes a transparent pressure part of the pressure device. The optics are designated 21 overall. It comprises three laser arrays 22, 23 and 24, which have mutually different wavelengths Lambda 1, Lambda 2, Lambda 3 of the respectively emitted laser beam. For example, in this embodiment of FIG. 2, differently colored microcapsules 41 are used which selectively respond to the different wavelengths lambda 1, lambda 2 or lambda 3. For example, only magenta-colored dye microcapsules could be burst by means of a laser beam from the laser diode array 22 with the wavelength lambda 1. Microcapsules with yellow dye respond, for example, only to a beam of wavelength lambda 2. The same applies to microcapsules of the color cyan, which respond to the laser beam with the wavelength lambda 3.

For the sake of clarity, the control devices used here for the individual laser diode arrays 22 to 24 are also not shown.

3 shows, in greatly enlarged representation, the Farb¬ ribbon 2 with spaced in the layer 4 microcapsules 41. The letters Y, M and C represent the respective color of the Druckf _^ rbstoffes contained in the respective microcapsules 4 and represent the well-known complementary colors Yellow, magenta and cyan. The laser beam of the laser diode array 23 with the wavelength lambda 1, which is focused on the layer of the microcapsules 41, can only burst microcapsules with the color magenta. This result is shown in FIG. 3. The leaking, magenta-colored liquid 25 wets or dyes the paper at the relevant location P, thus producing a printing dot (dot) with this color.

The reproduction of the color "black" can be improved if additional microcapsules with black printing ink are provided for this purpose.

Figure 4 shows the respective spectral absorption Y, M and C of the dyes yellow, magenta and Cyaπ. The figure also contains 4 shows the laser wavelength ranges Lambda 1, Lambda 2 and Lambda 3 for corresponding diode lasers. Selective absorber materials are used which respond to the respective wavelength lambda 1 or lambda 2 or lambda 3 and whose absorption spectrum is represented by A, A2 and A-. For example, copper-II-chloride is suitable as an absorber for the wavelength lambda 1 of the galllum aluminum arsenide laser diode. A microcapsule 41 of the color in which this absorber substance with the absorption spectrum A is contained can then be burst with the radiation of this laser diode. For example, in Figure 3 this is the color magenta.

The microcapsules 41 with the differently colored printing dyes contained therein can also be arranged in a pattern on the ink ribbon 2 or on its carrier film 3 with respect to the individual colors. This pattern can be periodically consecutive, parallel lines arranged according to colors. The microcapsules of a particular color can then be controlled by the laser radiation without the need for wavelength-selective measures. In this case, a laser diode array with a wavelength is sufficient to cover all colors, i.e. to control all lines in succession. However, it can also be used for e.g. d.ei colors three laser diode arrays are provided, each of which controls the rows of the respective assigned color. The multicolor print can thus also be carried out simultaneously. An advantage of such an embodiment is that it is not necessary for the microcapsules to respond selectively to (different) wavelength ranges of the focused laser radiation. It is therefore sufficient to provide a single absorber substance.

9 claims 4 figures

Claims

1. Device for laser transfer printing with at least one laser beam source (7; 22, 23, 24) for focused laser beam, with at least one electrical control device (12), with a receptacle for a print carrier (1), with a receptacle for an ink ribbon ( 2), with a pressure device (5, 6), between which the ribbon

(2) and the print carrier (1) are pressed against one another, this pressing device having a part (5) which is permeable to the laser beams (10, 11; Lambda 1, Lambda 2, Lambda 3), the ink ribbon (2) having a layer (4) with microcapsules (41) coated carrier film (3) is the carrier film

(3) is transparent to the laser wavelength used (lambda 1, lambda 2, lambda 3) and the microcapsules (41) contain the (respective) printing dye and the laser beams (10, 11, lambda 1, lambda 2, lambda 3) pass through the permeable part (5) of the pressure device (5, 6) and through the carrier film (3) hit the microcapsules (41) selected in accordance with the operation of the control device (12) and hit them at the point of impact for breaking up and for the transfer of the pressure dye (P) there the print carrier come.

2. Apparatus according to claim 1, so that the microcapsules (41) also contain a (respective) absorber material for the laser radiation.

3. Apparatus according to claim 1, g e k e n n z e i c h n e t d a d u r c h that the material of the wall of a respective microcapsule (41) is effective as an absorber.

4. Device according to one of claims 1 to 3, characterized in that the ink ribbon (2) contains microcapsules (41) which are filled with different printing dyes and looks- lent the individual colors (Y, M, C) in which layer (4) is finely distributed.

5. The device according to claim 4, characterized in that the printing dye (Y, M, C) contained in a respective microcapsule (41) is a printing dye which has an absorbing action for laser radiation of a respective wavelength range (Lambda 1, Lambda 2, Lambda 3) is.

6. The device according to claim 4, characterized in that a microcapsule (41) of a respective dye (Y, C, M) additionally contains a respective selective absorber substance which is sensitive to laser radiation of a respective wavelength range (Lambda 1, Lambda 2, Lambda 3) responds.

7. The device according to claim 4, characterized in that the material of the wall of a microcapsule (41) of a respective dye (Y, C, M) for laser radiation of a respective wavelength range (Lambda 1, Lambda 2, Lambda 3) is selectively absorbing .

8. The device according to claim 1, 2 or 3, characterized in that microcapsules (41), which are filled with different dyes (Y, M, C), with respect to the color (Y, M, C) of the printing dye contained in a pattern with a periodically alternating arrangement are arranged and the individual colors are controlled with the laser radiation.

9. Apparatus according to claim 8, so that the microcapsules (41) are arranged with respect to the color (Y, M, C) of the printing dye contained in periodically alternating parallel lines and these different colored lines are controlled with the laser radiation.