UA66516A - Device for laser engraving of flexographic plates - Google Patents

Abstract

Device for laser engraving of flexographic plates contains a rotating cylinder, at least, a double-beam laser engraving head that moves along the axis of cylinder, a control circuit of the beams of engraving head and an optical reading head of the mask area of the flexographic plate that is engraved by the first beam laser engraving head. A photopolymer plate with opaque coating is fastened on the rotating cylinder. The optical head is mechanically rigidly connected with the laser engraving head and it is electrically connected with the control circuit for correction of mask by the second beam of laser engraving head.

Description

Description of the invention

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

The device 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 computer-controlled focused laser radiation, creating a negative image necessary for the subsequent exposure and chemical processing of the photopolymer plate, which results in the formation of a flexoform with the necessary relief of printing elements designed to transfer ink to the print object.

The suitability of the final flexoform for use depends on the accuracy of the reproduction of the mask, that is, its correspondence to the original image file. In practice, during laser engraving of masks, there are 72 cases of incomplete removal of the mask material, omission of removal areas, removal of redundant areas, distortion of the shape of print elements. Failure at the mask engraving stage leads to significant economic losses.

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.

Known devices (1-3) 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, cudgel cylinder. But these devices do not solve the problem of control and correction of a laser-engraved flexoform mask.

A known device (4) for laser engraving of printing media of the anilox shaft type, in particular for flexography, 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, in particular the power and duration of the pulses of laser radiation, and the optical control the 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 as the engraving parameters drift over time. But the specified device is not capable of correcting already engraved cells.

Known devices |5, 6| for laser engraving of flexo printing forms using SIR technology, in which laser heads with two or more laser beams, which are formed by acousto-optic modulators, are used for the formation of a mask by removing the opaque layer. But in these devices there is no control of the engraved elements of the mask and the possibility of their correction. at

The closest to the invention is the device (Sugeitm Bidya! Itadeg Sotrasi of the Vagso firm, now "o

EzKko-Oharpisz I5|) for laser engraving of flexo printing forms using the SIR technology, in which to remove

The mask material is used for a laser head with two laser beams that are formed by an acousto-optic modulator. 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 the specified device does not have a scheme of current control of the engraved elements of the mask with "K feedback" to correct the defects of the mask during the engraving process. З7З 70 The invention is based on the task of improving the device for laser engraving of flexo printing forms, in which the correction of the shape and area of the engraved elements is ensured by introducing a system of optical control of the engraved mask of the flexo printing form. Due to this, the level of defects is reduced and the accuracy of manufacturing flexo printing forms is increased.

The problem is solved by the fact that in the device for laser engraving of flexo printing forms, which 79 contains a rotating cylinder with a fixed photopolymer plate, at least a two-beam laser

Ф engraving head and a control circuit that generates modulation signals with laser beams of the engraving machine

Ge") of the head, an additional optical head for reading the area of the flexoform mask engraved by the first beam of the laser engraving head is introduced, mechanically rigidly connected to the laser engraving head and electrically connected to the control circuit for feedback during the formation of the modulation signal - 70 of the second beam of the laser engraving head.

The proposed device ensures a reduction in the level of defects in the production of flexo printing forms at the expense of

Fo removal of mask elements not removed or incompletely removed by the first beam with the second beam of the laser engraving head. At the same time, the accuracy of the reproduction of the mask and the quality of the final form of flexo printing increases. 59 The essence of the proposed invention is explained by the drawing, which shows the scheme of the device for laser engraving of flexo printing forms.

The device includes a rotating cylinder 1, on which a photopolymer plate 2 with a light-proof coating is attached for the manufacture of a flexo printing form. The device includes a laser engraving head

C, at least two-beam, which moves along the axis of the cylinder 1. The device includes a control circuit 4 60 of the engraving head 3, which is the form of modulation signals of the laser beams of the engraving head 3. The device differs in that it includes an additional reading head 5, for example, with an optical circuit, similar to the scheme of the optical disk reading head, mechanically rigidly connected to the engraving head C and electrically connected to the control circuit 4.

The device works as follows. because the laser engraving head Z moves along the axis of the rotating cylinder 1 with a fixed on it,

for example, vacuum clamping with mechanical edge fixation, photopolymer plate 2 with an external opaque coating. The removal of the coating material is carried out by the radiation of a powerful laser, preferably in the near infrared range, which is effectively absorbed by the coating material with the removal of the latter, for example, Ma: MAC or fiber, divided, for example, by an acousto-optic modulator, into at least two beams. The first beam, which is used as the main working one, is focused by the optics of the laser head C on the coating of the plate 2 into a spot 6, which, when the cylinder 1 rotates, describes a spiral trajectory 7. The beam is modulated by a signal from the control circuit 4 in accordance with the raster image file that is being formed, for example bitmap image processor. The optical reading head 5 70 focuses a light beam, for example from a laser diode, into a spot 8, which lags behind the spot 6 by a distance of 0 "I/"i, where EI is the length of one turn of the spiral, moving along the same trajectory as the spot 6 The light reflected and scattered from the engraved area of the surface is collected by the optics of the head 5 on its photoreceptor. The readout signal, which is a function of the optical density of the etched layer, is fed to the control circuit 4, which compares it with the modulation signal of the first beam, delayed for a time db, corresponding to the shift I/ between spots 6 and 8, and these mesi fa de Mrejo (Kzha ) - the linear speed of the rotational movement of the point on the flexo plastic; c - cylinder rotation frequency, K - cylinder radius, a - plate thickness; M, - the speed of translational movement of the heads parallel to the axis of the cylinder. Based on the comparison of these signals, the control circuit forms a modulation signal for the second beam of the engraving head Z, with a delay, for example, for the time di-T-lu, where T is the period of rotation of the cylinder. The second beam, focused into the spot 9, moving along the same spiral trajectory 7 with a lag from the focal spot 6 of the first beam, for example, by the length of one turn of the spiral I, corrects the engraving of the mask by removing the areas of the coating not removed or incompletely removed by the first beam.

In an embodiment of the invention, in the presence of excessively large removed areas, the signal of the reading head is used by the control circuit to correct the power and pulse duration of the first beam, and in case of deviation of the parameters of the engraved mask above a level that cannot be corrected, the control circuit "issues a signal about the presence of an irreparable defect.

Sources of information 1. Yuaiu K.T., Kariap K.A. And azeg Tasvitie vuviet og epogamipou rgipiipud riageez. US Patent No. 3z636251, IPC No. 153/09, НО4М1/08, НО4М1/26, 1972. и-о 2. Vaag MU., Ooimez U). Meiyoa og (per rgodisiyop oi rgipiipu yogtv. US Patent Mo4013829, IPC НО4М1/06, 1977. h

Z. oItap R.M., Yuouie K.b. Arragaive Tog rgodisipd a zeatiezv soru iot ap ishpioipiei ogidipaI. Patent

USA Mo4232345, IPC НО4М1/22, НО4М1/26, НО4М1/38, 1980. and 4. Kobregiv 5.N., Rgosiog M. I azeg epogamipd arragaiiv. UMO patent Mo9402280, IPC В23К26/08, В41С1/05, 1984. (se) 5. mmlu.ezKo-dgarpisv.sopt/rhodisiazr: Sotryeg-iuo-RiIaie Peho: SOI Sotrasi (Sugeitm Bidna! Itadeg), 2003. b. Serpaga (A., Dasorzep T., Kevze! R., Zivipke O., Rivspeg 9U.-A. Meifod apa tiyireat zsappipud ademise i-o yog She ariayop oi Peho rgipipo riaieez ru Iazeg epdgamipd. US Patent Mo20020117067, IPC 841С1/ 00,

B41Mm6/00, 2002. "

Claims (1)

The formula of the invention is a device for laser engraving of flexo printing forms, which includes a rotating cylinder on which a photopolymer plate with a light-proof coating is attached, at least a two-beam laser engraving head moving along the axis of the cylinder, and a beam control scheme of the engraving head, 75 which differs by the fact that the device includes an additional optical head for reading the portion of the flexoform mask F engraved by the first beam of the laser engraving head, mechanically rigidly connected to (is) the laser engraving head and electrically connected to the control circuit for performing correction of the mask with the second beam of the laser engraving heads - 50 42) R 60 b5