Litho-strip with flat topography and printing plate produced therefrom - Patents.com

Abstract

The present invention relates to an aluminum alloy strip for a lithographic printing plate support having a rolled-formed surface topography on at least one surface of the strip, a method for producing the aluminum alloy strip, and a lithographic printing plate comprising a printing plate support made of the aluminum alloy. The object of the proposed aluminum alloy strip for a lithographic printing plate support is to provide a long useful life in the printing process even with a reduced thickness of the imaging coating, and to provide a roughened surface with a reduced charge carrier inflow, with the surface of the aluminum alloy strip being roughened to a thickness of ≦50 cm -1 , preferably ≦45 cm -1 or preferably ≦40 cm -1 This is realized by having the average number of peaks RPc measured perpendicular to the rolling direction of the aluminum alloy strip, and selecting c1 = +0.25 μm and c2 = −0.25 μm as the reference lines for RPc measurement.

Description

[Technical field]

[0001] The present invention relates to Use of an aluminium alloy strip for producing a lithographic printing plate or for producing a printing plate for waterless offset printing, An aluminum alloy strip for a lithographic printing plate support having a rolled-in surface topography on at least one strip surface, a method for producing said aluminum alloy strip and a lithographic printing plate support comprising a printing plate support made of an aluminum alloy. Or waterless offset printing This concerns the printed version for. [Background technology]

[0002] Very high demands are placed on the surface properties of lithostrips, i.e. aluminum alloy strips for lithographic printing plate supports. The lithostrips are usually subjected to an electrochemical roughening treatment, which must result in an extensive roughening and a uniform appearance. The roughened structure is important for the image-forming layer of the printing plate support produced from the lithostrip. A particularly flat lithostrip surface is therefore required, so that a uniformly roughened surface can be produced. The topography of the lithostrip surface is essentially an impression of the roller topography of the last cold rolling pass. The unevenness of the roller surface produces grooves (German: German ... The quality of the lithostrip surface and thus of the printing plate support is determined by the quality of the roller surface and thus by the polishing effect in the roller surface treatment, on the one hand, and the progressive wear of the roller, on the other hand.

[0003] According to the patent DE 10 200 03 13 567 A1, which is from the applicant, it was previously assumed that in the production of aluminum alloy strips for lithographic printing plate supports, rollers that have already been optimally polished are used, since too smooth a roller surface would lead to slippage between the roller and the litho strip due to low frictional forces on the litho strip surface, and thus to disturbances in the rolling process or damage to the aluminum strip. However, too rough a roller would result in a high or too high roughness of the aluminum alloy strip, so that the aluminum alloy strip is no longer suitable for the production of printing plate supports. Thus, the average roughness values ​​Ra of about 0.15 μm to 0.25 μm realized up to that point on the surface of the aluminum alloy strip were considered sufficient for many fields of application. Patent DE 10 200 03 13 567 A1 therefore proposes that the strip surface is treated by a pickling method with a specific pickling removal rate, after which it has a topography with a maximum peak height Rp and / or Sp of at most 1.4 μm, preferably at most 1.2 μm, in particular at most 1.0 μm.

[0004] According to other methods known from the prior art, for example the method known from DE 199 44 436 and the method known from DE 199 44 436, the litho strip is cleaned after rolling in order to remove the disturbing oxide islands on the surface of the strip and thereby improve the subsequent electrochemical roughening treatment.

[0005] US Pat. No. 5,399,633 discloses a printing plate support having a roughened and anodized surface with a maximum peak height Rp of up to 4 μm. Patent Document 5 discloses an aluminum alloy thin sheet for a can body of a beverage can and a method for manufacturing the beverage can, but does not disclose the use of the aluminum alloy strip for a lithographic printing plate. The same is true of Patent Document 6, which discloses an aluminum foil for electronic devices and a manufacturing method thereof. Examples of electronic devices include LCD displays, OLED displays, and electronic newspapers. Patent document 7 also relates only to a method for producing an aluminum alloy strip made of aluminum alloy type 1100 in a humidity-conditioned state H14 for producing high-quality cosmetic bottle caps, and does not disclose a support for a lithographic printing plate or the lithographic printing plate itself. Patent document 8 is an invention related to the manufacture of aluminum alloy foils. The only uses of these foils are disclosed as packaging materials for chemicals and food. Patent Document 9 is an invention related to the manufacture of aluminum foil for ultraviolet reflective materials. Patent Document 9 also does not disclose the use of aluminum alloy strips for lithographic printing plate supports. Patent Document 10 discloses a printing plate carrier for a lithographic printing plate, but only discloses the surface characteristics of a roughened printing plate made of an aluminum alloy and having a photosensitive coating.

[0006] For current printing plate supports, especially for the new "on-press development" printing plate supports, the thickness of the imaging coating is constantly decreasing to reduce development time and save manufacturing costs. In addition, softer imaging coatings are also being used, which also save costs in the manufacture of the printing plate support, but which are reduced in thickness during the press run. The aluminum alloy strips produced so far for lithographic printing plate supports are not optimally adapted to these additional challenges. It has also been shown that chemical pickling cannot solve this problem. Thus, printing plate supports produced from known aluminum alloy strips tend to have a short useful life in printing processes using the new printing plate supports.

[0007] Finally, the aluminum alloy strip is usually electrochemically roughened to produce the printing plate support. It is also desirable to reduce the charge carrier influx required for uniform roughening of the surface of the printing plate support facing the imaging coating.

[0008] In addition to the arithmetic mean roughness Ra, the height Rp of the maximum profile peak of the roughness profile (i.e. the peak height), the depth Rv of the maximum profile valley (i.e. the trough depth) and the number of peaks RPc as defined in Non-Patent Documents 1 and 2, as well as the contact area ratio Smr(c) and the aspect ratio Str of the surface texture as defined in Non-Patent Document 3, are important for determining the surface quality of litho strips and electrochemically roughened printing plate supports.

[0009] The surface parameters Ra, Rp, Rv, RPc, Smr(c) and Str mentioned here refer to optical area-specific measurements on measurement areas of at least 4.5 mm x 4.5 mm, measured with a confocal microscope (with an in-plane measurement point spacing of 1.6 μm or less) and determined with an analysis software. For this purpose, area-specific optical measurements of these parameters were carried out on three measurement areas of the aforementioned size and the arithmetic mean of each parameter was determined. The profile parameters Ra, Rp, Rv and RPc are calculated for each measurement area perpendicular to the rolling direction as the arithmetic mean value from the profile section of the area-specific measurements obtainable. The measurement data are prepared by shape compensation (F-filter) using a second order polynomial. A Gaussian filter with λc=250 μm is used as waviness filter. There is no filtering of fine roughness. For Rp, Rv, RPc and Smr(c), the values ​​thus determined are given as the mean peak height Rp, the mean trough depth Rv, the mean number of peaks RPc and the mean areal load factor Smr (c=+0.25 μm).

[0010] For the surface area ratio Smr(c), the surface areas oriented in the rolling direction are of particular importance, in particular the ratios of grooves and webs oriented in this direction, which are generated by rolling and are generally not removed by electrochemical roughening. However, these can be detected by isolating and inverting the ratios in the rolling direction after a Fourier transform of the measured surface, and then the surface area ratio Smr(c=+0.25 μm) of these structures is determined from the inverted surface ratios.

[0011] The isotropy of the roughening of the printing plate support is specified by the aspect ratio Str of the surface texture according to Non-Patent Document 3. For the calculation of the Str value, the number of measurement points in the measurement area is multiplied by a power of 2. The multiplied value is calculated by a resampling operation.

[0012] The average number of peaks RPc measured perpendicular to the rolling direction typically indicates the number of convex areas present as a roller web on the aluminium alloy strip, while the arithmetic mean roughness value Ra and the average peak height Rp provide information about the height of these convexities in the topography of the aluminium alloy strip or printing plate support.

[0013] The mean areal mass fraction Smr(c=+0.25 μm) provides information about the surface fraction of the investigated surface that lies above a specific intersection line with the material fraction curve (Abbott curve) chosen here with c=+0.25 μm. Thus, the surface fractions of the convex areas of the surface, e.g. the surface portions oriented in the rolling direction (German: Oberflaechenanteile, English: surface portions), are shown to be located above the reference line c=+0.25 μm in the material fraction curve of the aluminum alloy strip or printing plate support.

[0014] The ratio of the average peak height Rp to the average trough depth Rv indicates whether the surface topography is dominated more by troughs (values ​​< 1) or more by peaks (values ​​> 1). The Rp / Rv ratio is nearly independent of the charge carrier influx during electrochemical roughening. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] European Patent Application Publication No. 2 444 254(A2) [Patent Document 2] International Publication No. 2006 / 122852(A1) [Patent Document 3] International Publication No. 2007 / 141300(A1) [Patent Document 4] European Patent Application Publication No. 0 778 158(A1) [Patent Document 5] Patent Publication No. 2015-004095 [Patent Document 6] European Patent Application Publication No. 3 254 772(A1) [Patent Document 7] China Patent Application Publication No. 110102580(A) [Patent Document 8] Patent Publication No. 2002-224710 [Patent Document 9] US Patent Application Publication No. 2019 / 0076897(A1) [Patent Document 10] European Patent Application Publication No. 1 172 228(A2) [Non-patent literature]

[0016] [Non-Patent Document 1] German Industrial Standards European Standards International Standardization Organization (DIN EN ISO) No. 4287 [Non-Patent Document 2] German Industrial Standard European Standard (DIN EN) No. 10049 [Non-Patent Document 3] DIN EN ISO No. 25178 Summary of the Invention [Means for solving the problem]

[0017] Therefore, the object of the present invention is to Use of an aluminum alloy strip for lithographic printing plates and for printing plates for waterless offset printing; Aluminum alloy strip for lithographic printing plate support provides long useful life in the printing process even with reduced thickness of imaging coating and can be roughened with lower charge carrier flux and, Furthermore, the present invention provides a method for producing an aluminum alloy strip having desired properties, Print version, In particular, "on-press" printing with a long useful life Edition or for waterless offset printing Version The purpose of this document is to provide

[0018] This object is achieved by the subject matter of claims 1-16.

[0019] According to the first teaching of the present invention, the surface of the aluminum alloy strip is ≦50 cm -1 , preferably ≦45cm -1 or particularly preferably ≦40 cm -1 of average peak numbers RPc measured perpendicular to the rolling direction of the aluminium alloy strip, with c1 = +0.25 μm and c2 = -0.25 μm being chosen as the reference lines for RPc measurement. It has been shown that the aluminium alloy strip can be further improved in terms of suitability for the manufacture of printing plate supports by optimising the surface topography rolled during the final cold rolling pass, since the aluminium alloy strip according to the invention allows to extend the useful life of very thin imaging coatings.

[0020] It is believed that a reduction in the average number of peaks RPc allows for an increase in the useful life since the raised areas present on the strip perpendicular to the rolling direction are significantly reduced. The aluminum strip according to the invention is therefore particularly preferably used as a printing plate support for "on-press developed" printing plates and printing plates for waterless offset printing.

[0021] In the first embodiment of the present aluminum alloy strip, the surface of the aluminum alloy strip also has an average peak height Rp of maximum 1.1 μm, preferably 0.45 μm to 1.1 μm. The reduction of the average peak height Rp also further ensures that the height of the roller web, if present, is reduced, contributing to an improved useful life.

[0022] This also applies to further embodiments of the aluminium alloy strip, in which the average area mass ratio Smr(c=+0.25 μm) in % of the surface portion of the aluminium alloy strip oriented in the rolling direction is at most 5%, at most 4% or at most 3.5% if only the surface portion which is the result from the Fourier transform of the surface in the rolling direction is taken into account. A reduction in the average area mass ratio Smr(c=+0.25 μm) of the surface portion of the aluminium alloy strip oriented in the rolling direction reduces the length and width of the rolled web on the aluminium alloy strip. A rolled web according to the present finding with reduced length and width improves the useful life of printing plates produced from the aluminium alloy strip according to the present invention.

[0023] To study the rolled web, area-based surface roughness measurements are carried out optically. After polynomial fitting (second order) of the raw data and removal of the waviness components with the help of a Gaussian filter (limit wavelength 250 μm), height data are available in the form of a matrix a of dimensions N×M. This matrix is ​​transformed by a discrete Fast Fourier Transform (FFT) into frequency space, which allows separating the surface moduli extending in the rolling direction from those perpendicular to the rolling direction.

[0024]

number

[0025] Fourier component of the surface ratio oriented in the rolling direction c jk is transformed back to the local space.

[0026]

number

[0027] The average areal mass ratio Smr(c=+0.25 μm) of the surface parts oriented in the rolling direction is then determined by evaluating the back-transformed surface ratios. For this purpose, a material mass ratio curve in the form of an Abbott curve is generated from the back-transformed data, and the areal mass ratio Smr(c=+0.25 μm) is determined as the intersection of the material mass ratio curve with the straight line at c=+0.25 μm.

[0028] Preferably, the thickness of the aluminum alloy strip according to the further embodiment is 0.10 mm to 0.5 mm, preferably 0.10 mm to 0.4 mm. In particular, aluminum strips having a thickness of 0.10 mm to 0.4 mm are used for lithographic printing plate supports. Special types also use thicknesses between 0.4 mm and 0.5 mm.

[0029] According to the following embodiment of the aluminum alloy strip, the aluminum alloy strip has the following composition: 0.02% by weight≦Si≦0.50% by weight, preferably 0.02% by weight≦Si≦0.25% by weight, 0.2% by weight≦Fe≦1.0% by weight, preferably 0.2% by weight≦Fe≦0.6% by weight, Cu≦0.05 wt.%, preferably ≦0.01 wt.%, Mn≦0.3% by weight, preferably <0.1% by weight, particularly preferably ≦0.05% by weight; 0.05% by weight≦Mg≦0.6% by weight, preferably 0.1% by weight≦Mg≦0.4% by weight, Cr≦0.01wt%, Zn≦0.1% by weight, preferably ≦0.05% by weight, Ti≦0.05wt%, The balance is Al and impurities up to 0.05 wt.% individually and up to 0.15 wt.% in total. has.

[0030] A Si content of 0.02wt%-0.50wt% also affects the appearance of the electrochemically roughened printing plate support. If the Si content is less than 0.02wt%, an excessive number of dents will be generated in the aluminum strip during electrochemical roughening. If the Si content is too high, exceeding 0.50wt%, the number of dents in the roughened aluminum strip will be too low and the distribution will be non-uniform. Preferably, a Si content of 0.02wt%≦Si≦0.25wt% is used.

[0031] Even low copper contents have a detrimental effect on the electrochemical roughening treatment, therefore the Cu content is ≦0.05 wt.%, preferably ≦0.01 wt.%.

[0032] Iron contributes to the mechanical and thermal strength of the aluminum alloy strip, so 0.2wt%-1wt% iron is permitted. Further increases in content lead to worsening of the roughening behavior during electrochemical roughening. The preferred Fe content is between 0.2wt%-0.6wt% or between 0.4wt%-0.6wt%.

[0033] Magnesium ensures an increase in strength, especially in the state of the hard-rolled printing plate support. At the same time, too much magnesium can have a negative effect in terms of the properties during further processing and electrochemical roughening due to too high strength. Therefore, the aluminum alloy preferably has a Mg content of 0.05% by weight≦Mg≦0.6% by weight. In the preferred range of 0.1% by weight≦Mg≦0.4% by weight or 0.25% to 0.4% by weight, a strip with high strength in the hard-rolled state and a process-reliable roughening behavior can be provided.

[0034] Manganese increases the charge carrier influx required for the electrochemical roughening of the printing plate support produced from the aluminum alloy strip as well as the thermal strength of the aluminum alloy strip, and is therefore limited to 0.3% by weight, preferably <0.1% by weight, particularly preferably ≦0.05% by weight.

[0035] In order to achieve good surface roughening behavior, Cr, Zn and Ti are also limited: the contents are Cr≦0.01 wt.%, Zn≦0.1 wt.%, preferably ≦0.05 wt.%, Ti≦0.05 wt.%.

[0036] Finally, the aluminum alloy strip is in a work-hardened state according to the following embodiment, which results in improved handling during the production of the printing plate support. Due to the magnesium content, the aluminum alloy strip has a relatively high strength in these states, which allows good processing during electrochemical surface roughening and during the application of the image-forming layer in strip form. For example, as hard-hardened state, the state H18 produced by cold rolling with intermediate annealing or the state H19 produced by cold rolling without intermediate annealing is used.

[0037] According to a further teaching of the present invention, a method for producing an aluminum alloy strip according to the invention is provided, in which a rolling ingot is cast from the aluminum alloy for the lithographic printing plate support, optionally preheated or homogenized before hot rolling, the rolling ingot is hot rolled to a hot strip, the hot strip is then cold rolled to a final thickness with or without intermediate annealing, and a work roll having an average roughness Ra of less than 0.18 μm, preferably less than 0.17 μm or preferably at most 0.15 μm is used in the final cold rolling pass. The surface topography of the litho strip is essentially determined by the surface topography of the work roll in the final cold rolling pass. It has been shown that the method according to the invention can produce an aluminum alloy strip that can be further processed to a printing plate support with an improved useful life in printing. A long useful life in printing is also achieved, in particular with a thin imaging coating, for "on-press developed" printing plates or printing plates for waterless offset printing.

[0038] The average roughness Ra of the work roll is determined according to DIN EN ISO No. 4287, the roller surface according to the invention having an average roughness Ra of less than 0.18 μm, preferably less than 0.17 μm or preferably at most 0.15 μm, at least parallel to the longitudinal axis of the work roll.

[0039] It has also been shown that according to a preferred embodiment of the method, the work rolls in the final cold rolling pass have a roller surface with a mean trough depth R measured parallel to the longitudinal axis of the work roll of up to 1.2 μm, which has achieved particularly good results in providing the aluminium strip topography according to the invention.

[0040] If work rolls having an average roughness Ra of at least 0.07 μm, preferably at least 0.10 μm, are used in the final cold rolling pass, slippage between the rolls and the litho strip can be reliably avoided, providing a stable production process contrary to conventional belief.

[0041] According to a next embodiment of the method, in order to achieve sufficient imprinting of the surface topography of the roller surface in the final cold rolling pass, the degree of unrolling in the final cold rolling pass is at least 20%, preferably at least 30%.

[0042] In order to provide as problem-free a surface as possible and at the same time allow the most economical production of the aluminium alloy strip, the degree of reduction in the final cold rolling pass is at most 65%, preferably at most 60%.

[0043] According to a further teaching of the present invention, there is provided a lithographic printing plate comprising a printing plate support made from an aluminum alloy, in particular made from an aluminum alloy strip according to the present invention, at least the surface of the printing plate support facing the image-forming layer having an areal mass ratio Smr(c=+0.25 μm) of less than 5%, less than 4.5% or at most 4% of the surface portion oriented in the rolling direction after electrochemical roughening of the printing plate support. It has been shown that a reduction in the areal mass ratio Smr(c=+0.25 μm) can significantly improve the useful life of this printing plate in printing.

[0044] In particular, after electrochemical roughening, the use of the aluminum alloy strip according to the invention showed a significant reduction in the mean areal mass ratio Smr (c=+0.25 μm) to less than 5% or less than 4.5% or even up to 4%, which further improves the useful life of the printing plate in printing.

[0045] According to a further embodiment of the printing plate, the surface of the printing plate support facing at least the image-forming layer after electrochemical roughening of the printing plate support has a ratio Rp / Rv of average peak height to average trough depth of at most 0.45, preferably at most 0.4. This specific ratio of average peak height to average trough depth defines the topography of the surface of the printing plate support independent of the charge carrier influx during electrochemical roughening, and the average peak height is smaller than half the average trough depth. Thus, the topography of the printing plate support is dominated by troughs and is formed very flat in the direction of the imaging coating, which significantly improves the useful life of thin coatings in printing, such as the coatings of printing plates for "on-press development" printing plates or waterless offset printing.

[0046] After electrochemical roughening, preferably at least the side of the printing plate support facing the image-forming layer has an average peak height Rp of less than 1.2 μm, at most 1.1 μm or preferably at most 1 μm. By reducing the absolute value of the average peak height Rp, an improvement in the useful life of printing plates, such as "on-press development" printing plates or printing plates for waterless offset printing, can also be realized. This is realized, for example, by using the aluminum alloy strip according to the present invention.

[0047] If the printing plate support is produced from an aluminum alloy strip according to the invention, the printing plate support can also be uniformly or isotropically roughened at lower charge carrier influxes. The aluminum alloy strip according to the invention already exhibits a high aspect ratio Str of the surface texture at low charge carrier influxes. Thus, according to one embodiment, the aspect ratio Str of the surface texture is at least 500 C / dm 2 The surface of the printing plate support facing at least the image-forming layer after electrochemical roughening at a charge carrier influx has a texture aspect ratio Str according to DIN EN ISO 25178 of at least 50%. The texture aspect ratio Str is a measure of the uniformity of the texture. At a value of 100% or 1 the texture is isotropic, i.e. direction-independent. Thus, the printing plate support according to the invention already provides a high texture aspect ratio Str even at low charge carrier influxes, which reduces the effort required for electrochemical roughening. This allows printing plates to be produced at lower costs.

[0048] This is 400C / dm 2 This also applies to a further embodiment of the printing plate, in which at least the surface of the printing plate support facing the image-forming layer after electrochemical roughening with a charge carrier influx of at least 20% reaches a texture aspect ratio Str according to DIN EN ISO 25178 of at least 20%.

[0049] Finally, according to a further embodiment, the waterless offset printing plate according to the invention has a printing plate support made from an aluminum alloy strip according to the invention. The imaging coating of the waterless offset printing plate also has a particularly low thickness, so that the useful life of the waterless offset printing plate benefits greatly from the surface topography of the aluminum alloy strip. However, the printing plate support for the waterless offset printing plate is not electrochemically roughened before being coated for imaging.

[0050] The invention is further explained by means of embodiments, for which purpose reference is made to the following tables and drawings. [Brief description of the drawings]

[0051] [Figure 1] 4 shows the optically measured measurement surfaces of comparative litho strips electrochemically roughened at different charge carrier influxes as a false color representation of the height values. [Diagram 2] 4 shows the optically measured measurement surfaces of comparative litho strips electrochemically roughened at different charge carrier influxes as a false color representation of the height values. [Diagram 3] 4 shows the optically measured measurement surfaces of comparative litho strips electrochemically roughened at different charge carrier influxes as a false color representation of the height values. [Figure 4] 4 shows the optically measured measurement surfaces of comparative litho strips electrochemically roughened at different charge carrier influxes as a false color representation of the height values. [Diagram 5] 4 shows the optically measured measurement surfaces of electrochemically roughened litho-strips according to the invention with different charge carrier influxes as a false colour representation of the height values. [Figure 6] 4 shows the optically measured measurement surfaces of electrochemically roughened litho-strips according to the invention with different charge carrier influxes as a false colour representation of the height values. [Figure 7]4 shows the optically measured measurement surfaces of electrochemically roughened litho-strips according to the invention with different charge carrier influxes as a false colour representation of the height values. [Figure 8] 4 shows the optically measured measurement surfaces of electrochemically roughened litho-strips according to the invention with different charge carrier influxes as a false colour representation of the height values. [Figure 9] 1 shows a material ratio curve in the form of an Abbott curve for determining the areal load factor Smr(c).

[0052] The litho strips, whose measurement surfaces are shown in Figs. 1 to 8, have the following composition: 0.02% by weight≦Si≦0.50% by weight, preferably 0.02% by weight≦Si≦0.25% by weight, 0.2% by weight≦Fe≦1.0% by weight, preferably 0.2% by weight≦Fe≦0.6% by weight, Cu≦0.05 wt.%, preferably ≦0.01 wt.%, Mn≦0.3% by weight, preferably <0.1% by weight, particularly preferably ≦0.05% by weight; 0.05% by weight≦Mg≦0.6% by weight, preferably 0.1% by weight≦Mg≦0.4% by weight, Cr≦0.01wt%, Zn≦0.1% by weight, preferably ≦0.05% by weight, Ti≦0.05wt%, The remainder is Al and impurities up to 0.05 wt.% individually and up to 0.15 wt.% in total. The alloy was manufactured from a rolling ingot made of an aluminum alloy having a diameter of 10 mm or less.

[0053] The production is carried out by casting a rolling ingot, homogenizing the rolling ingot at 450-610 °C for at least 1 hour, hot rolling the rolling ingot into a hot strip having a thickness of about 2-7 mm, and bringing the hot strip to its final thickness by cold rolling with or without intermediate annealing.

[0054] In the final cold rolling pass, the litho strip according to the invention according to figures 5 to 8 uses work rolls with a surface topography of less than 0.18 μm, preferably at most 0.17 μm or at most 0.15 μm, an arithmetic mean roughness Ra according to DIN ISO No. 4287. The average trough depth Rv of the surface of the work rolls according to the embodiment according to the invention was at most 1.2 μm.

[0055] On the other hand, the comparative litho strips of Figures 1 to 4 were cold rolled using work rolls with an arithmetic mean roughness Ra of 0.22 μm to 0.25 μm in the final cold rolling pass. The mean trough depth Rv was also higher in the work rolls used according to the invention, at a maximum value of 1.6 μm. The sheets produced in this way were cold rolled at 400 C / dm in HCl as electrolyte. 2 ~800C / dm 2 The surfaces were electrochemically roughened with various charge carrier influxes.

[0056] The optically measured height values ​​of the measuring surface areas are shown in false color in Figs. 1 to 8, with the depressions being assigned gray to black shades and the protrusions being assigned light gray to white-gray shades. The human eye can already detect the differences in the measuring surfaces illustrated in this way in the unroughened state. The litho-strip according to the invention thus exhibits a significantly less structured surface in the rolling direction. This effect intensifies with increasing roughening.

[0057] Further measurements were carried out on litho-strips of embodiments a, b, c, d and m having an aluminum alloy composition according to Table 1 and comparative examples f, g, h.

[0058] All values ​​of Rp, RPc, Rv, Ra, Smr and Str of the measured embodiments and comparative examples were optically measured in three measurement areas of size 4.5 mm x 4.5 mm using a confocal microscope and determined with an analysis software (MountainsMap® by Digital Surf). The measurement areas were randomly arranged in an area of ​​DIN A4 size on the strip and on the printing plate support. There was no surface damage at the corresponding points on the strip. The arithmetic mean of the three measurement areas for each parameter was calculated, and the profile parameters Rp, RPc, Rv, Ra perpendicular to the rolling direction were calculated as the arithmetic mean value in the measurement areas. The measurement data was prepared by shape compensation (F filter) using a second order polynomial. A Gaussian filter with λc = 250 μm was used as waviness filter. Micro-roughness was not filtered.

[0059] Litho strips a, b, c, d and m were identically produced by the method described above starting with casting of the rolling ingots, homogenization of the rolling ingots, hot rolling of the rolling ingots and cold rolling of the hot strips to final thickness with (H18) and without (H19) intermediate annealing.

[0060] The resulting thickness, material condition and arithmetic mean roughness value Ra of the surface of the resulting litho-strip are specified in Table 1. The different roller topographies used for the final cold rolling pass can be found in Table 7.

[0061] Thus, the litho strip according to the invention was cold rolled in the final cold rolling pass with the indicated degrees of reduction using work rolls having a roller surface with an arithmetic mean roughness Ra of 0.11 μm to 0.17 μm according to table 7. The mean trough depth Rv was measured to be less than 1.2 μm. Between 40% and 55%, the degrees of reduction were in the range of at least 20% according to the invention. Furthermore, at a maximum of 55%, the degrees of reduction were less than 60% or 65%, so that good surface properties were achieved with the lowest possible number of rolling passes.

[0062] The arithmetic mean roughness values ​​Ra of the roller surfaces of the work rolls in the final cold rolling pass of the comparative strips were between 0.22 μm and 0.25 μm. At a maximum value of 1.6 μm, the mean trough depth Rv was also significantly higher than in the work rolls used according to the invention.

[0063] In the manufacture of embodiments according to the invention, contrary to conventional opinion of experts, a stable manufacturing process has been demonstrated in which there are no disruptions during cold rolling due to slippage between the cold rolling and the rolled litho strip.

[0064] The first differences between the comparative strips and the lithostrips according to the invention were found in the arithmetic mean roughness values ​​Ra of the lithostrips according to the invention a, b, c, d and m. At 0.09 μm to 0.11 μm, these were significantly lower than the values ​​of the comparative strips f, g and h, which have about 0.19 μm. These values ​​of the arithmetic mean roughness value Ra perpendicular to the rolling direction are the result of the provision of a roller surface with an arithmetic mean roughness value Ra of less than 0.18 μm.

[0065] The aluminum strips a, b, c, d and m according to the invention were also cut to 50 cm -1 The average number of peaks measured perpendicular to the rolling direction, RPc, was significantly smaller than that of the 68 cm -1 The comparative example strips, having a smaller average number of peaks RPc, significantly surpassed the results of the aluminium strip according to the invention.

[0066] At the maximum value of 0.74 μm, the average peak height Rp in the aluminum alloy strip according to the invention is also significantly smaller than the average peak height Rp of the comparative example strip having an average peak height Rp of at least 0.88 μm, and this lower average peak height Rp is believed to be due to the lower roller surface trough depth Rv.

[0067] The average areal mass factor Smr (c=+0.25 μm) of the surface parts oriented in the rolling direction was significantly lower in the embodiment according to the invention. Figure 9 shows, by way of example, how the areal mass factor Smr(c) can be determined for a value c from the material fraction curve in the form of an Abbott curve. The value c=0 results in a material fraction of 100% as can be seen in Figure 9. The c-value is read on the Z-axis, which corresponds to the height value of the surface topography. To determine the areal mass factor Smr(c), the intersection point of the material fraction curve with the straight line Z=c is determined and the corresponding material fraction is read on the X-axis.

[0068] To determine the average areal mass ratio Smr(c=+0.25 μm), the optical measurement results are subjected to Fourier transform roughness measurement as described above, and only the surface masses oriented in the rolling direction are inverted. From the inverted surface data, the material fraction curve and the value for the areal mass ratio Smr(c=+0.25 μm) are determined, as shown in FIG. 9. From the areal mass ratio Smr(c=+0.25 μm) determined in the three measurement areas of the surface portion oriented in the rolling direction, the arithmetic mean was then calculated to determine the average areal mass ratio Smr(c=+0.25 μm).

[0069] The average area bearing ratio Smr(c=+0.25 μm) of the surface portion oriented in the rolling direction of the aluminum alloy strip according to the invention was a maximum of 3.79%, significantly smaller than 5%. On the other hand, the area bearing ratio Smr(c=+0.25 μm) of the surface portion oriented in the rolling direction of the comparative example strip was at least 8.09%, which was more than twice as high as the maximum average area bearing ratio Smr(c=+0.25 μm) of the surface portion oriented in the rolling direction of the aluminum strip according to the invention.

[0070] The printing plate supports made from the aluminum strips according to the invention showed a significantly improved useful life in printing when using "on-press development" coatings compared to the comparative examples. This is believed to be due to differences in surface topography. The same is believed to be true for printing plates for waterless offset printing.

[0071] The properties of aluminium strips in electrochemical roughening were tested using HCl as the electrolyte and various charge carrier inputs. The electrolyte concentrations were 6 g / L HCl and 1 g / L Al in the form of AlCl3 at 25-30°C. 3+ and 20A / dm 2 A current density of AC was used.

[0072] 1 to 8 have already shown that charge carrier influx causes small dips, shown in black in these figures, which increase in number with increasing charge carrier influx.

[0073] At the same time, the electrochemical roughening also affects other surface parameters of the surface of the aluminum alloy strip facing the imaging coating of the printing plate.

[0074] The printing plate supports produced from electrochemically roughened aluminum strips showed a significant difference in the average areal mass ratio Smr (c=+0.25 μm) of the surface parts oriented in the rolling direction, as can be seen in Table 4. The printing plate supports according to the invention have a significantly lower average areal mass ratio Smr (c=+0.25 μm) of the surface parts oriented in the rolling direction, this ratio being especially significant at 700 C / dm 2 or 800C / dm 2 The average area mass ratio Smr(c=+0.25 μm) of the surface area oriented in the rolling direction is reduced even more at very high charge carrier influx at 1000 μm. A similar behavior is observed in the comparative strip, albeit at a much higher level. Overall, the electrochemical roughening of the comparative strip does not reduce the average area mass ratio Smr(c=+0.25 μm) of the surface area oriented in the rolling direction below the lower limit of 4%.

[0075] The aluminum strip according to the invention also showed a ratio Rp / Rv of up to 0.45, with the majority of the values ​​being below 0.41. As expected, the dependence on the charge carrier influx during electrochemical roughening was very low. The comparative examples were significantly higher than these values.2 and 500C / dm 2 A value of 0.43 for the charge carrier influx could only be measured in comparative example f.

[0076] However, the printing plate supports according to the invention produced from test strips a, b, c, d and m had a 600 C / dm 2 The strips showed ratios Rp / Rv of 0.40 to 0.34, thus significantly lower Rp / Rv ratios than in the comparative strips. The surface topography of the printing plate support according to the invention was therefore designed to be even flatter than in the case of the printing plate support produced from the comparative strips.

[0077] The study of the aspect ratio Str of the surface texture after electrochemical roughening showed a significant difference. The aspect ratio Str is a measure of the isotropy of the roughened surface. The value Str reaches 100% when the surface is completely isotropic. The printing plate supports a, b, c, d and m produced from the test strips according to the invention were subjected to a 500 C / dm 2 At least 20% or 400C / dm 2 While the comparative strip already provides a surface texture aspect ratio Str of at least 50% at 700 C / dm 2 In the case of the sintered body, the surface texture has an aspect ratio Str of at least 20%.

[0078] This means that the aluminum strip according to the invention can provide an isotropically roughened surface with less charge carrier influx and can therefore be processed into printing plates more economically, while at the same time providing a longer useful life for printing plates having very thin imaging coatings.

[0079] Table 1. Composition of the test strips in wt.%, the remainder being Al, unavoidable impurities up to 0.05 wt.% individually and up to 0.15 wt.% in total, arithmetic mean roughness Ra perpendicular to the rolling direction as defined in DIN EN 10049, condition H18 with intermediate annealing during cold rolling, condition H19 without intermediate annealing

[0080] [Table 1]

[0081] Table 2. Surface measurements of aluminium alloy strip after rolling, mean peak height Rp, mean number of peaks RPc, defined in accordance with DIN EN ISO 4287 and DIN EN 10049, with a calibrated optical roughness measuring system, Smr, defined in accordance with DIN EN ISO 25178, with a calibrated optical roughness measuring system

[0082] [Table 2]

[0083] Table 3. Average peak height Rp as defined in DIN EN ISO 4287 as a function of charge carrier influx for electrochemical roughening in HCl on roughened printing plate supports

[0084] [Table 3]

[0085] Table 4. Area coverage Smr at c=+0.25 μm in % according to DIN EN ISO 25178 as a function of charge carrier influx for electrochemical roughening in HCl on roughened printing plate supports

[0086] [Table 4]

[0087] Table 5. The ratio Rp / Rv in each case as defined in DIN EN ISO 4287 as a function of the charge carrier influx for electrochemical roughening in HCl on the roughened printing plate support

[0088] [Table 5]

[0089] Table 6. Surface aspect ratio Str according to DIN EN ISO 25178 as a function of charge carrier influx for electrochemical roughening in HCl on roughened printing plate supports

[0090] [Table 6]

[0091] Table 7. Arithmetic mean roughness Ra of roller surface according to DIN ISO 4287

[0092] [Table 7]

Claims

1. 1. Use of an aluminum alloy strip for producing a printing plate for a lithographic printing plate support or for waterless offset printing, the printing plate having a roll-formed surface topography on at least one surface of the strip, comprising: The surface of the aluminum alloy strip is ≦50 cm －１ an average number of peaks RPc measured perpendicular to the rolling direction of the aluminum alloy strip; c1 = +0.25 μm and c2 = -0.25 μm are selected as reference lines for the RPc measurement, and the average number of peaks RPc is determined from area-by-area optical measurements in three measurement areas of at least 4.5 mm × 4.5 mm using a confocal microscope with an in-plane measurement point spacing of 1.6 μm or less; The arithmetic mean value of the profile parameter RPc measured perpendicular to the rolling direction in the measurement zone is calculated from the profile section of the zone-specific measurements obtainable for each measurement zone perpendicular to the rolling direction, the arithmetic mean value being calculated from three measurement zones for the parameter, The measurement data preparation is carried out by shape compensation using a quadratic polynomial (F-filter) and a Gaussian filter with λc=250 μm as waviness filter, no fine roughness filtering is performed.

2. The use according to claim 1 ,

2. 1. An aluminum alloy strip for a lithographic printing plate support having a roll-formed surface topography on at least one strip surface, said aluminum alloy strip having the following composition: 0.02% by weight≦Si≦0.50% by weight, 0.2% by weight≦Fe≦1.0% by weight, Cu≦0.05% by weight, Mn≦0.3% by weight, 0.05% by weight≦Mg≦0.6% by weight, Cr≦0.01% by weight, Zn≦0.1% by weight, Ti≦0.05% by weight, The balance is Al and impurities up to 0.05 wt.% individually and up to 0.15 wt.% in total; having The surface of the aluminum alloy strip is ≦50 cm －１ an average number of peaks RPc measured perpendicular to the rolling direction of the aluminum alloy strip; c1 = +0.25 μm and c2 = -0.25 μm are selected as reference lines for the RPc measurement, and the average number of peaks RPc is determined from area-by-area optical measurements in three measurement areas of at least 4.5 mm × 4.5 mm using a confocal microscope with an in-plane measurement point spacing of 1.6 μm or less; The arithmetic mean value of the profile parameter RPc measured perpendicular to the rolling direction in the measurement zone is calculated from the profile section of the zone-specific measurements obtainable for each measurement zone perpendicular to the rolling direction, the arithmetic mean value being calculated from three measurement zones for the parameter, The measurement data preparation is carried out by shape compensation using a quadratic polynomial (F-filter) and a Gaussian filter with λc=250 μm as waviness filter, no fine roughness filtering is performed. The aluminum alloy strip is characterized in that

3. The surface of the aluminum alloy strip has an average peak height Rp of up to 1.1 μm, the peak height Rp being determined from area-by-area optical measurements in three measurement areas of at least 4.5 mm x 4.5 mm using a confocal microscope with an in-plane measurement point spacing of 1.6 μm or less; The arithmetic mean value of the profile parameter Rp measured perpendicular to the rolling direction in the measurement zone is calculated from the profile section of the zone-specific measurements obtainable for each measurement zone perpendicular to the rolling direction, the arithmetic mean value being calculated from three measurement zones for the parameter, The measurement data preparation is carried out by shape compensation using a quadratic polynomial (F-filter) and a Gaussian filter with λc=250 μm as waviness filter, no fine roughness filtering is performed.

3. An aluminium alloy strip according to claim 2 , characterized in that

4. the average area material ratio Smr(c=+0.25 μm) in % of the surface portion of the surface of the aluminium alloy strip oriented in the rolling direction is at most 5% when only the surface portion resulting from a Fourier transform of the surface in the rolling direction is considered; The average areal mass ratio Smr (c=+0.25 μm) is determined from area-by-area optical measurements in three measurement areas of at least 4.5 mm×4.5 mm using a confocal microscope having an in-plane measurement point spacing of 1.6 μm or less; The arithmetic mean value is calculated from the three measurement areas for the average areal mass ratio Smr (c=+0.25 μm), The measurement data preparation is carried out by shape compensation using a quadratic polynomial (F-filter) and a Gaussian filter with λc=250 μm as waviness filter, no fine roughness filtering is performed.

4. An aluminium alloy strip according to claim 2 or 3.

5. The aluminum alloy strip according to any one of claims 2 to 4, characterized in that the aluminum alloy strip has a thickness of 0.10 mm to 0.5 mm.

6. The aluminum alloy strip according to any one of claims 2 to 5, characterized in that the aluminum alloy strip has a hard-rolled condition.

7. 7. A method for producing an aluminum alloy strip for a lithographic printing plate support according to claim 2, wherein a rolling ingot is cast from the aluminum alloy for the lithographic printing plate support, optionally preheated or homogenized before hot rolling of said rolling ingot, said rolling ingot being hot rolled to a hot strip, said hot strip then being cold rolled to a final thickness with or without intermediate annealing, characterized in that in the final cold rolling pass work rolls are used which have an average roughness Ra according to DIN ISO 4287 of less than 0.18 μm.

8. 8. The method according to claim 7, characterized in that work rolls having an average roughness Ra according to DIN ISO 4287 of at least 0.07 μm are used in the final cold rolling pass.

9. 9. The method according to claim 7 or 8, characterized in that the reduction in the final cold rolling pass is at least 20%.

10. 10. The method according to claim 7, wherein the reduction in the final cold rolling pass is at most 65%.

11. 1. A lithographic printing plate comprising a printing plate support made from an aluminum alloy, at least the surface of the printing plate support facing the image-forming layer has an average areal mass ratio Smr (c=+0.25 μm) of the surface parts oriented in the rolling direction after electrochemical graining of the printing plate support, when only the surface ratio resulting after Fourier transformation of the surface in the rolling direction is taken into account, of less than 5%, The average areal mass ratio Smr (c=+0.25 μm) is determined from area-by-area optical measurements in three measurement areas of at least 4.5 mm×4.5 mm using a confocal microscope having an in-plane measurement point spacing of 1.6 μm or less; The arithmetic mean value is calculated from the three measurement areas for the average areal mass ratio Smr (c=+0.25 μm), The measurement data preparation is carried out by shape compensation using a quadratic polynomial (F-filter) and a Gaussian filter with λc=250 μm as waviness filter, no fine roughness filtering is performed. A lithographic printing plate comprising:

12. after electrochemical roughening of said printing plate support, at least the surface of said printing plate support facing said imaging layer has a ratio of an average peak height Rp to an average trough depth Rv of up to 0.45, said average peak height Rp and said average trough depth Rv being determined from area-by-area optical measurements in three measurement areas of at least 4.5 mm x 4.5 mm using a confocal microscope with an in-plane measurement point spacing of 1.6 μm or less, The arithmetic mean values ​​of the profile parameters Rp and Rv measured perpendicular to the rolling direction in the measurement zones are calculated from the profile sections of the zone-specific measurements obtainable for each measurement zone perpendicular to the rolling direction, the arithmetic mean values ​​being calculated from three measurement zones for the parameters, The measurement data preparation is carried out by shape compensation using a quadratic polynomial (F-filter) and a Gaussian filter with λc=250 μm as waviness filter, no fine roughness filtering is performed.

12. The printing plate according to claim 11.

13. after electrochemical roughening of the printing plate support, at least the surface facing the imaging layer has an average peak height Rp of less than 1.2 μm, the peak height Rp being determined from area-by-area optical measurements in three measurement areas of at least 4.5 mm×4.5 mm using a confocal microscope with an in-plane measurement point spacing of 1.6 μm or less; The arithmetic mean value of the profile parameter Rp measured perpendicular to the rolling direction in the measurement zone is calculated from the profile section of the zone-specific measurements obtainable for each measurement zone perpendicular to the rolling direction, the arithmetic mean value being calculated from three measurement zones for the parameter, The measurement data preparation is carried out by shape compensation using a quadratic polynomial (F-filter) and a Gaussian filter with λc=250 μm as waviness filter, no fine roughness filtering is performed.

13. The printing plate according to claim 11 or 12.

14. At least 500 C / dm ２ at least the surface of the printing plate support facing the image-forming layer after electrochemical roughening with a charge carrier influx of at least 50% has a texture aspect ratio Str according to DIN EN ISO 25178, the texture aspect ratio Str being determined from area-by-area optical measurements on three measurement areas of at least 4.5 mm x 4.5 mm using a confocal microscope with an in-plane measuring point spacing of 1.6 μm or less, said arithmetic mean value being calculated from three measurement areas for said parameter; The measurement data preparation is carried out by shape compensation using a quadratic polynomial (F-filter) and a Gaussian filter with λc=250 μm as waviness filter, no fine roughness filtering is performed. The printing plate according to any one of claims 11 to 13.

15. At least 400 C / dm ２ at least the surface of the printing plate support facing the image-forming layer after electrochemical roughening with a charge carrier influx of at least 20% has a texture aspect ratio Str according to DIN EN ISO 25178 of at least 20%, the texture aspect ratio Str being determined from area-by-area optical measurements on three measurement areas of at least 4.5 mm x 4.5 mm using a confocal microscope with an in-plane measurement point spacing of 1.6 μm or less, said arithmetic mean value being calculated from three measurement areas for said parameter; The measurement data preparation is carried out by shape compensation using a quadratic polynomial (F-filter) and a Gaussian filter with λc=250 μm as waviness filter, no fine roughness filtering is performed.

15. The printing plate of claim 14.

16. A printing plate for waterless offset printing comprising a printing plate support comprising an aluminum alloy strip for a lithographic printing plate support, the aluminum alloy strip having a roll-formed surface topography on at least one strip surface, The aluminum alloy strip has the following composition: 0.02% by weight≦Si≦0.50% by weight, 0.2% by weight≦Fe≦1.0% by weight, Cu≦0.05% by weight, Mn≦0.3% by weight, 0.05% by weight≦Mg≦0.6% by weight, Cr≦0.01% by weight, Zn≦0.1% by weight, Ti≦0.05% by weight, The balance is Al and impurities up to 0.05 wt.% individually and up to 0.15 wt.% in total; having the surface of the aluminum alloy strip has an average number of peaks RPc, measured perpendicular to the rolling direction of the aluminum alloy strip, of ≦50 cm −1 ; c1 = +0.25 μm and c2 = -0.25 μm are selected as reference lines for the RPc measurement, and the average number of peaks RPc is determined from area-by-area optical measurements in three measurement areas of at least 4.5 mm × 4.5 mm using a confocal microscope with an in-plane measurement point spacing of 1.6 μm or less; The arithmetic mean value of the profile parameter RPc measured perpendicular to the rolling direction in the measurement zone is calculated from the profile section of the zone-specific measurements obtainable for each measurement zone perpendicular to the rolling direction, the arithmetic mean value being calculated from three measurement zones for the parameter, The measurement data preparation is carried out by shape compensation using a quadratic polynomial (F-filter) and a Gaussian filter with λc=250 μm as waviness filter, no fine roughness filtering is performed. A printing plate for waterless offset printing.

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