UA69064A - Method for laser engraving of flexographic printing plates - Google Patents

Abstract

Method for laser engraving of the flexographic printing plates, at which on the photopolymer plate is formed the negative image in the form of a mask by removal of the opaque layer by two laser modulated beams. The section engraved by the first laser beam is read by the optical head of backward motion and in case of incomplete removal of the coating material the signal of modulation of the second laser beam is generated, which performs the correction of defects of the mask engraving.

Description

Description of the invention

The invention relates to printing equipment, namely to pre-press equipment for the production of 2 flexographic forms.

The method is intended for laser engraving of masks on photopolymer plates with a light-proof layer in the process of manufacturing flexographic printing forms using the digital technology "computer-printing form" (Sotri(eg-o-Riaiye, or SIR).

According to the existing technology, the mask material is removed by focused laser radiation, which creates a 70 negative image, which is necessary for the subsequent exposure and chemical processing of the photopolymer plate. As a result, a flexoform with the necessary relief of printing elements is formed.

The suitability of the final flexoform for use and the quality of the resulting image depend on the mask's correspondence to the original image file. In practice, during laser engraving of masks, there are cases of incomplete removal of the mask material, omissions of removal areas, removal of redundant areas, 12 distortion of the shape of print elements. A defect that was not noticed at the stage of mask engraving leads to significant economic losses during printing.

The invention is aimed at improving the quality of flexoform mask engraving due to ongoing control and correction of mask elements during the engraving process.

There are known methods (|1, 2), in which a signal from the head, in particular laser, "reading" of the original is used to modulate the radiation of the laser "writing" on the printing, in particular flexographic, copy cylinder. But these devices do not solve the problem of control and correction of a laser-engraved flexoform mask.

In the device |IZ| for laser engraving of anilox shaft type printing media, in particular for flexography, a method is used in which the engraving head moves along the axis of the shaft and engraves a series of cells, the control circuit 22 sets the engraving parameters, and the optical control device monitors the profile of the engraved cells and produces a control signal in such a way as to further maintain the desired cell profile when the engraving parameters drift over time. But the specified device is not capable of correcting already engraved cells.

The closest to the invention is the method of laser engraving of flexo printing forms using the SIR technology described in HER, in which a laser head with two laser beams formed by an acousto-optic modulator is used to remove the mask material. The head moves along the axis of a rotating cylinder with a fixed photopolymer plate with a light-proof layer, and the engraving of the mask is carried out by two beams at the same time. But this method does not involve current control of engraved mask elements with dz feedback to correct mask defects during the engraving process.

The invention is based on the task of improving the quality of manufacturing flexographic printing forms using the "computer-printing form" technology by introducing a scheme for optical control of mask engraving and correcting emerging defects directly in the process of its production. The use of the invention will make it possible to reduce the level of defects in the production of flexoforms by reducing the number of unremoved or incompletely removed elements of the mask, correcting the shape and area of engraved elements. WITH

The problem is solved due to the fact that after engraving, the area is illuminated by a probing beam and the signal is received by the reading head. This signal is compared with the modulation signal of the first beam

With" taking into account the delay i, corresponding to the shift I between the processing and probing spots, and -i/shika) , where i is the frequency of rotation of the cylinder, KE is the radius of the cylinder, 0 is the thickness of the plate (the contribution of the translational movement can be neglected, since the linear the speed of rotational movement of the cylinder in real conditions is 4-5 orders of magnitude higher than the speed of movement of the heads). Based on the comparison of these signals, if necessary, the control circuit forms a modulation signal for the second beam of the engraving head, which moves with some lag along the path of the first beam. o An example that confirms the possibility of implementing the invention can be the device shown in drawing 50. The device includes a rotating cylinder 1 actuated by a servo drive (not shown in the drawing), (o) on which a photopolymer plate 2 with a light-proof coating for making a mold is attached

T" of flexo printing. The device includes a laser engraving head C, at least two-beam, which uses the radiation of a powerful laser (not shown in the drawing), which is effectively absorbed by the coating material with the removal of the latter. The engraving head focuses the laser beams on the surface of two plates 2 in spots 4 and 5. The device includes a control circuit 6 for the laser head 3. The device differs in that it contains an additional reading head 7, for example, with an optical circuit, for feedback. similar to the scheme of the optical CD-ROM reading head, mechanically rigidly connected to the engraving head 3. The head 7 focuses a light beam of low intensity into a spot 8 on the surface of the plate 2. The signal of the head 7 is used by the control circuit 6 to correct the engraving of the mask on the plate 2. in Sources of information 1. Yuaiu K.T., Kariap K.A. And azeg Tasvitie vuviet og epogamipou rgipiipud riageez. US patent Mo3z636251, IPC No. 153/09, НО4М1/08, НО4М1/26, 1972. 2. Vaag MU., Ooimez U). Meiyoa og (per rgodisiyop oi rgipiipu yogtv. US patent Mo4013829, IPC НО4М1/06, 1977.

Z. Kobregiz 5.N., Rgosiog M. And azeg epogamipud arragaiv. Patent MO Mo9402280, IPC В23К26/08, В41С1/05, 1984. ve 4. Serpagaghi A. dasobzep T., Kezze! R., ZieipKe O., Rizspeg U.-A. MeiShoy apa tiyreat zsappipud demise yog She ariayop oi Peho rgipipo riaiez ru Iazeg epdgamipd. US patent Mo20020117067, IPC 841С1/00,

B41Mm6/00, 2002.

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Claims (1)

The formula of the invention is the method of laser engraving of flexo printing forms, which consists in the fact that a negative image in the form of a mask is formed on a photopolymer plate with a light-proof coating by removing the light-proof layer with at least two modulated laser beams, which differs in that the area engraved by the first laser beam is read by the optical head of the reverse communication, and in the case of incomplete removal of the coating material, a second laser beam modulation signal is formed, which corrects the mask engraving defects. 29 Official Bulletin "Industrial Property". Book 1 "Inventions, useful models, topographies of integrated "microcircuits", 2004, M 8, 15.08.2004. State Department of Intellectual Property of the Ministry of Education and Science of Ukraine. " (Se) "c) (22) (Se) - with . and? (22) se) ("c) FO c" 60 b5