DD217645A1 - METHOD FOR THE PRODUCTION OF FLAT PRINTING FORMS WITH LASER RADIATION - Google Patents

Abstract

The method for producing planographic printing forms with laser radiation is applicable in graphic arts. The object, which is solved by the invention, consists in the energetic optimization of the recording process in the information recording on non-photosensitive material. According to the invention, the sensitizing dyes in the non-photosensitive layer are distributed in such a way that a concentration gradient arises perpendicular to the printing plate surface.

Description

Title of the Brfinduing:

Method for producing planographic printing forms with laser radiation

Field of application of the invention

The invention relates to the production of printing plates for flat or offset printing by irradiation with a laser.

Characteristic of the known technical

Lifting the very expensive photosensitive compounds, copying layers of non-photosensitive materials are also used for lithographic printing. Thus, in DS 24 48 325 describes a method in which a non-photosensitive hydrophilic material by laser irradiation is hydrophobic and thus farbführend 'Ua to adjust the spectral sensitivity of the copy layer to the laser used, are used in accordance with DS 25 43 dyes, the absorb the spectral emission range of the laser. According to the claims, the dyes preferably 4-5% ₉ of the layer weight are used in amounts of 1-80. Wt.% Is used. The pure dyes may also be used as non-photosensitive hydrophilic material. A disadvantage of the proposed method is that

that as a result of the high dye concentrations, the incident light is completely absorbed in a very thin surface layer, so that depending on the applied layer thickness continuous hydrophobing of the entire copy layer is difficult or prevented. Ss comes to the known negative phenomena such as deterioration of the AuflSsungsbehavior and detachment of the bridging elements.

Siel the invention

is to substantially improve the printing properties such as printability and resolution of the offset printing plates produced by laser irradiation of a non-photosensitive hydrophilic matrial.

Explanation of the essence of the invention

In accordance with the invention, homogeneous absorption of the incident light over the entire layer thickness is achieved. This is done by creating a concentration gradient of the dye such that the concentration of the dye decreases continuously or stepwise from the lowest layer area on the carrier to the surface of the copy layer _. so that the same light intensities are absorbed in all layer depth regions when the concentration gradient is given correspondingly ,

Additional improvement can be achieved by the fact that the concentration of the paraffin first decreases from the surface to the middle of the layer, passes through a minimum there and then re-exalts. The concentration of the paraffin concentration in this embodiment of the invention lies at the boundary between stratum and frage aateria.

Sine further possibility aur improving the homogeneous absorption of the incoming laser radiation is in the choice of a Farbstoffkonaentration in the range of "0.05 to 1 _wt.%%

example 1

On an anodized aluminum Aluminiumattatta with an oxide layer thickness of 8 / um 3 Polyvinylalkoholschichten were each of 4 / Um thickness with a content of 35, 0.1 and 0.35 wt. % Crystal Violet deposited. This layer was sit eiaeia argon laser

2

a power density of 4 »5 kW / ma 60> u s.lang irradiated pointwise · With this plate could be printed without prior development ·

Example 2 -V

Ao? an anodized aluminum plate with an oxide thickness ron θ yuxa polyvinyl alcohol is added with an addition of 20 wt. % Kristaliviolett in a layer thickness of 20 / Um. This layer will

/ · ''

irradiated with an argon laser with a power density of 4.5 kW / mn . Dia pulse duration was 60 yus. After the irradiation, the plate was developed with water, whereby the irradiated points stopped. However, accession to aaschliessendeη pressure experiments, the Druckalemente took turns "3ine similar hergestallte plate, but with a Parbstof fk onsentration of 0.39 percent"% proved to be suitable printing technology. , '

Example 3 . , ',

On an anodically oxidized aluminum plate with an oxide layer thickness of 8 / μm, 3 polyvinyl alcohol layers of 5 μm thick were successively added

, '. '4

a content of 35, 3.5 and 0.35 Qe ^ *% Sristallviolett applied. This plate was treated ^ ie in Example 2 · The form obtained also proved capable as pressure · - ^i.

Claims (3)

Erfindungaansprach 1. A process for the production of Flachdruckf orsaen by laser irradiation-with one or more matched to the wavelength of the laser used dyes offset non-photosensitive, hydrophilic material on a rager, characterized in that a Konsantrationsgradient the sensitizing dye produced perpendicular to the surface of the! Liragers becomes. 2. The method according to item 1, characterized in that the Farbstoffkonaentration of the interface! Carrier / layer to the surface continuously or gradually decreases. 3. Method according to item 1, characterized in that; that the concentration of the dye starting from the surface initially decreases and then assumes again, wherein the concentration Masimuia is close to the carrier / layer interface t. Process according to item 1, characterized in that the concentration of the pigment per cent by weight is greater than 0.05, with a concentration of less than 1 Ge *. % of the? arbst off gradient may go against Ulll.