FR2695350A1 - Cylinder of printing machine. - Google Patents

Abstract

Printing machine cylinder having a surface coating. The coating (14) contains metallic silicon (Si metallic) or consists of metallic silicon, the surface (15) of which is preferably softened, then polished and then advantageously impregnated with a pore sealant so that its surface roughness reaches a value of 1.5 to 1.0 mum. Application advantageously to a metering cylinder of the wetting mechanism of an offset printing machine.

Description

The invention relates to a printing machine cylinder, in

  particular to a cylinder of the moistening mechanism, preferably to a metering roll comprising a

surface coating.

  There is a demand in machine construction technique for cylinders having a

  surface coating having a hydrophilic nature.

  By taking the printing technique as an example, the moistening mechanism of a printing machine generally comprises multiple cylinders whose function is to transfer such a thin film of wetting agent.

  as possible on the plate of a cylinder

  Particularly thin and regular distribution of wetting agent makes it possible to obtain a good impression It is moreover important that the wetting agent supply be done without infiltration of printing ink into the wetting mechanism. The ink is particularly troublesome in the arrangements in which at least one intermediate cylinder connects the rolls of the inking mechanism with those of the moistening mechanism. Best is the hydrophilic nature of the surface of the cylinders of the printing machine (cylinders of the dampening mechanism), thinner and regular is the

  wetting film that forms.

  A high-quality printing, for example an art print, is generally preceded by an extremely thin film of wetting agent, for example from / ln, to the surface of the cylinder. a film of wetting agent having this thinness, to mix this agent with alcohol or an alcohol substitute to reduce the surface tension. The alcohols used were, for example, isopropanol or ethanol. in the future, a reduction of alcohol or alcohol substitutes will be required or even decreed for the protection of the environment and / or to meet accident protection requirements. a layer of wetting agent

  extremely thin and regular nevertheless remains desirable.

  Specific surface coating materials which have been subjected to a specific treatment have been used up to now in addition to special impregnating agents (alcohols) to obtain hydrophilic characteristics as good as possible from the cylinders of the machines. print It is known to use a special steel softened and / or polished surface material of these damping mechanism cylinders It is also known to deposit galvanically on the cylinder surface a layer of chromium which is then softened and / or The buffing mechanism cylinders mentioned above make it possible to obtain good printing results in conjunction with the use of alcohols or alcohol substitutes in the wetting agent. However, the proportion of alcohol or substitute of alcohol is reduced, the print results are not

satisfactory.

  The subject of the invention is therefore a printing machine cylinder of the type specified in the preamble which has

  excellent hydrophilic qualities.

  According to an essential feature of the invention, the coating comprises metallic silicon (metallic Si) or is composed of metallic silicon. This coating according to the invention has the effect that the contact angle of the wetting agent without alcohol is extremely small The angle of contact is the angle formed by the secant of a drop of wetting agent with a flat surface on which the drop is located. The extreme smallness of the contact angle makes it possible to avoid require more than a small amount of lowering of the surface tension of the wetting agent by addition of alcohol or alcohol substitute, since even in the absence of this precaution, the wetting agent film is formed The coating with the material according to the invention can be provided on a single cylinder or also on several cylinders of the printing machine or the moistening mechanism of this machine. to perform the coating according to the invention on the metering roll of the moistening mechanism. It is possible to deposit an intermediate layer of Ni and / or Cr and / or Al and / or B and / or Si and / or Ti and / or Mo or the like between the surface (the casing) of the cylinder and the coating to provide protection against corrosion and / or to improve adhesion Deposition of the layer is preferably carried out by a thermal spraying method, a physical vapor deposition process (PVD), a chemical vapor deposition (CVD) process, a chemical vapor deposition (CVD) process under plasma or by

galvanic way.

  In the definition of the invention, the term "includes" leaves open the way for substances other than metallic silicon in the coating. The phrase "consists of" specifies that the coating is made

  exclusively using metallic silicon.

  According to another particularity of the invention, the coating is produced by thermal deposition, in particular by spraying silicon metal powder (powder

Si metal).

  The coating preferably has a thickness

  about 0.2 mm to 2 mm, preferably about 1 mm.

  According to another particularity of the invention, the coating has a surface roughness Rz <5 μm, preferably Rz, 1.0 μm. This surface roughness is obtained by a corresponding treatment of the metal silicon layer, in particular by softening , polishing and additional pore sealing treatment (for example

  example by an anaerobic curing adhesive).

  It is particularly possible that the coating

  or a PVD layer (PVD = Physical Vapor Deposition).

  A layer of EBPVD (EBPVD = Electron Beam Physical Vapor

  Deposition) may in particular be provided.

  It is also possible, according to another embodiment of the invention, for the coating to be a CVD layer (CVD = Chemical Vapor Deposition). It can be provided as a variant that the coating

  a layer made by sintering.

  It is also possible that the coating is a layer produced by isostatic compression at

hot.

  It is finally possible also that the

  coating is a galvanic layer.

  According to an advantageous embodiment of

  the invention, the cylinder is metal.

  The invention also relates to a process for coating a cylinder of a printing machine, metallic silicon or a substance containing silicon.

  metal being deposited on the surface of the cylinder.

  The metallic silicon or the substance containing metallic silicon is advantageously deposited thermally, in particular by thermal spraying on

the surface of the cylinder.

  It is expected, according to another phase of the process, that the surface of the coating is machined to reduce its

  roughness This machining can in particular be mechanical.

  The surface is preferably softened, then polished and optionally is subjected to a complementary treatment

  pore sealing (to an impregnation).

  The machining of the surface is advantageously

  performed up to a roughness <1.0 μm.

  In particular, it is provided that the surface of the coating is cleaned with a basic agent, in particular with a weakly basic cleaning product, in particular after the above-mentioned machining of equalization (such as, for example, softening and / or polishing ) This results in an activation of the surface that causes the

formation of a hydrophilic layer.

  According to another feature of the invention, the roughness of the surface of the coating consisting of metallic silicon or comprising metallic silicon is adjusted so that a wetting agent without alcohol and / or without an alcohol substitute and intended to be used for the printing process has a contact angle

<50, in particular <40.

  The invention furthermore relates to the use of metallic silicon for producing a coating of the surface of a cylinder of a machine

  print that has a hydrophilic nature.

  The invention will be described in more detail with reference to the accompanying drawings, in which: FIG. 1 is a diagram of the rolls of an offset printing machine; FIG. 2 is a partial perspective view of a wetting mechanism cylinder which has a coating and FIG. 3 is a graph of the contact angle of the surface of a cylinder as a function of the

  content of the wetting agent in isopropanol.

  FIG. 1 represents a diagram 1 of the cylinders

  of a printing group of an offset printing machine.

  The cylinders 2 to 6 are part of a wetting mechanism 7 and the other cylinders shown in this figure are part of an inking mechanism 8 The cylinder 6 represents an intermediate cylinder; it connects the wetting mechanism 7 to the inking mechanism 8 One of the rolls of the inking mechanism 8 is assigned to an inkwell 9 on which the printing ink is taken. The cylinder 2 of the wetting mechanism 7, which is shaped as a plunger, is assigned to a water tank 10 on which the wetting agent (the wetting water) is taken and transmitted to the cylinder 3 constituting a metering cylinder The cylinder 3 rotates against the cylinder 5 shaped as a cylinder of rubber and cooperating with the cylinder 4 which assumes the function of a transfer cylinder The cylinder 5 transmits the wetting water in the form of a thin film and regular to a cylinder 11 which carries a cliché to the circumference Other cylinders such as a blanket cylinder, etc. are not shown in Figure 1 for the sake of simplicity. At least one of the cylinders, namely the metering roll 3, has a coating which has excellent hydrophilic characteristics, so that a wetting agent film is formed which is extremely thin and even without being necessary to add this alcohol agent or an alcohol substitute or the content of which alcohol or alcohol substitute alcohol is significantly reduced Alcohol, which generally represents a volumetric proportion of 10% to 15%, therefore its content considerably reduced or even completely suppressed This factor is of particular importance according to the accident protection regulations or

  even for the protection of the environment.

  The invention is however not limited to the arrangement of the cylinders of the wetting mechanism 7 represented by FIG. 1, but can be used for all types of cylinders of printing machines when these

  must have a hydrophilic nature.

  FIG. 2 is a cross-section perspective view of the cylinder 3 (the metering cylinder). It consists of a hollow cylinder 12 of metal whose surface 13 comprises a coating 14. The coating 14 contains metallic silicon or, alternatively,

composed of metallic silicon.

  A pure silicon metal powder is preferably deposited by thermal spraying in a layer having very few pores and preferably having a thickness of about 1 mm. Next, this coating undergoes mechanical softening and then polishing until its roughness Rz is approximately 1.0 μm, in particular <1.0 μm. The surface is optionally then subjected to a complementary La pore sealing treatment.

  surface thus produced has excellent hydrophilicity.

  This hydrophilicity is reproducible and also remains

  fully preserved even after drying of the surface.

  The surface of the coating 14 preferably undergoes after polishing and thus before its first use - cleaning with a weakly basic product. This results in activation of the surface with formation.

a hydrophilic layer.

  A coating 14 of the wetting mechanism cylinder made according to the method of the invention has a contact angle of a wetting agent containing no alcohol and / or no alcohol substitute which is less than

  (see Figure 3).

  The graph of FIG. 3 represents the contact angle Vk of the surface of the metering cylinder (cylinder 3) which comprises a coating as described. In the graph, the contact angle c, indicated in degrees, is plotted as a function of the Isopropanol content A, which is indicated on the abscissa, in volumetric percent With the coating of the invention, the functional relationship follows line 16 The graph clearly shows that even in the absence of addition of alcohol, the angle Ote contact is extremely low For comparison, Figure 3 shows contact angles of dampening mechanism cylinders with known surfaces. Line 17

  represents the result for a chrome coated cylinder.

  Finally, line 18 represents the result for a surface of a wetting mechanism cylinder which is in

special steel.

  The fact that a thermally sprayed metallic silicon coating can be softened and polished particularly quickly and simply to a roughness Rz of about 1.5 μm, preferably about 1.0 μm, is extremely It is possible without any difficulty to obtain, with the aid of a coating made in this manner, wetting agent film thicknesses which, for example, have only 5 μm even without any impregnating agent in the coating. mooring water and therefore the printing can be carried out impeccably, without any

  tearing of the wetting agent film.

  Other processes than that of thermal spraying mentioned above can also be used for

  depositing the coating 14 on the surface 13 of the cylinder 12.

  It is possible to advantageously use PVD processes, EBPVD processes, CVD processes, plasma CVD processes, sintering processes, hot isostatic pressing processes and / or

galvanic processes.

Claims (19)

  A printing machine cylinder, in particular a wetting mechanism cylinder, preferably a dosing cylinder having a surface coating, characterized in that the coating (14) contains metallic silicon   (If metallic) or consists of metallic silicon.   Printing machine cylinder according to Claim 1, characterized in that the coating (14) is produced by thermal deposition, in particular by thermal spraying of metallic silicon powder. (of Si metal powder).   3 Printing machine cylinder according to one or   the other of the preceding claims, characterized in that   that the coating (14) has a thickness of about 0.2 to 2 mm, preferably about 1 mm.   4 Cylinder printing machine according to one   any of the preceding claims, characterized in that   the coating (14) has a surface roughness Rz   <5 μm, preferably Rz 4 1.0 μm.   5 Cylinder printing machine according to one   any of the preceding claims, characterized in that   that the coating (14) is a layer of PVD (a layer   physical vapor deposition).   6 Printing machine cylinder according to one   any of claims 1 to 4, characterized in that   the coating (14) is a layer of EBPVD (deposit   electron beam vapor phase physics).   7 Printing machine cylinder according to one   any of claims 1 to 4, characterized in that   the coating (14) is a CVD layer (deposit layer chemical vapor phase).   8 Print machine cylinder according to one   any of claims 1 to 4, characterized in that   the coating (14) is a plasma CVD layer   (chemical vapor deposition layer under plasma).   9 Printing machine cylinder according to one   any of claims 1 to 4, characterized in that   the coating (14) is a layer produced by sintering.   Cylinder printing machine according to one   any of claims 1 to 4, characterized in that   the coating (14) is a layer produced by compression isostatic hot.   11 Printing machine cylinder according to one   any of claims 1 to 4, characterized in that   the coating (14) is a galvanic layer.   12 Printing machine cylinder according to one   any of the preceding claims, characterized in that   the cylinder (12) is made of metal.   13 A process for coating a cylinder of a printing machine, in particular for producing a printing machine cylinder according to any one of   preceding claims, characterized in that   metallic silicon or a silicon-containing substance   metal is deposited on the surface (13) of the cylinder (12).   Process according to Claim 13, characterized in that the metallic silicon or a silicon metal powder or the substance containing metallic silicon is deposited on the surface (13) by thermal spraying.   Process according to one or the other   Claims 13 and 14, characterized in that the surface   the coating (14) is machined to reduce the roughness. Process according to any one of   Claims 13 to 15, characterized in that the surface of the   coating (14) undergoes softening.   Process according to any one of   Claims 13 to 16, characterized in that the surface of the   coating (14) undergoes polishing, in particular after the softening.   Process according to any one of   Claims 13 to 17, characterized in that the surface of the   the coating (14) is impregnated with a sealing agent   pores to reduce porosity.   19 Process according to any one of   Claims 13 to 18, characterized in that the surface of the   coating (14) undergoes machining until a roughness Rz 4 1.0 μm.   Process according to any one of   Claims 13 to 19, characterized in that the surface of the   coating is cleaned by a basic agent, in particular by a weakly basic cleaning product, especially after the machining of equalization (such as softening, etc.).   21 Process according to any one of   Claims 13 to 20, characterized in that the roughness   the surface of the coating (14) consisting of metallic silicon or metal silicon-containing material is adjusted so that a wetting agent is used for the printing process and is not supplemented with alcohol and / or of an alcohol substitute has an angle of   contact <50, in particular <35.   22 Use of metallic silicon or a substance containing silicon metal for producing a surface coating of a cylinder of   printing machine having hydrophilic characteristics.