CA2102347A1 - Low affinity coating blanket for rotary offset presses - Google Patents
Low affinity coating blanket for rotary offset pressesInfo
- Publication number
- CA2102347A1 CA2102347A1 CA002102347A CA2102347A CA2102347A1 CA 2102347 A1 CA2102347 A1 CA 2102347A1 CA 002102347 A CA002102347 A CA 002102347A CA 2102347 A CA2102347 A CA 2102347A CA 2102347 A1 CA2102347 A1 CA 2102347A1
- Authority
- CA
- Canada
- Prior art keywords
- coating
- blanket
- low affinity
- blanket assembly
- transfer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
- B41N10/00—Blankets or like coverings; Coverings for wipers for intaglio printing
- B41N10/02—Blanket structure
- B41N10/04—Blanket structure multi-layer
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
- B41N2210/00—Location or type of the layers in multi-layer blankets or like coverings
- B41N2210/02—Top layers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
- B41N2210/00—Location or type of the layers in multi-layer blankets or like coverings
- B41N2210/14—Location or type of the layers in multi-layer blankets or like coverings characterised by macromolecular organic compounds
Landscapes
- Printing Plates And Materials Therefor (AREA)
Abstract
LOW AFFINITY COATING BLANKET
FOR ROTARY OFFSET PRESSES
ABSTRACT
The transfer layer (28) of a coating blanket (10) has a low affinity for liquid coating material or ink, rather than a high affinity which characterizes convention-al nitrile rubber and photopolymer blankets. The low affinity material, for example a fluorinated polymer or a silicone elastomer, resists wetting by the liquid media, and has a tendency to form a non-spreading bead or droplet of the liquid coating material on the transfer media surface. The low affinity surface provides smooth and quick release of the substrate from the nip between the coating blanket cylinder (12) and the impression cylinder (20). The low affinity transfer surface further inhibits the accumulation of ink and/or liquid coating material, thereby preventing split images, ghost images, offset images and back-trapping defects.
FOR ROTARY OFFSET PRESSES
ABSTRACT
The transfer layer (28) of a coating blanket (10) has a low affinity for liquid coating material or ink, rather than a high affinity which characterizes convention-al nitrile rubber and photopolymer blankets. The low affinity material, for example a fluorinated polymer or a silicone elastomer, resists wetting by the liquid media, and has a tendency to form a non-spreading bead or droplet of the liquid coating material on the transfer media surface. The low affinity surface provides smooth and quick release of the substrate from the nip between the coating blanket cylinder (12) and the impression cylinder (20). The low affinity transfer surface further inhibits the accumulation of ink and/or liquid coating material, thereby preventing split images, ghost images, offset images and back-trapping defects.
Description
. ~
% ~ 7 LOW AFFINITY COATING BLANKET
FOR ROTARY OFFSET PRESSES
This invention relates generally to sheet-fed or web-fed, rotary offset or flexographic printing presses, and more particularly to an improved coating blanket for the application of protective and/or decorative coatings to the printed surface of freshly printed sheets or web stock.
In rotary offset printing, an image which is to be reproduced on a sheet of paper or some other print stock is formed on a printing plate which is attached to the surface of a rotatable plate cylinder. The image is not printed directly from the plate onto the paper, but is first transferred to an intermediate ink transfer blanket, which is mounted on a rotatable blanket cylinder. The blanket transfers (offsets) the inked image to a sheet of paper which is fed through the nip between a rotatable impression cylinder and the blanket cylinder. The ofPset printing press thus includes a plate cylinder which carrieæ
the printing image, a blanket cylinder which has an ink transfer surface for receiving the inked image, and an impression cylinder which presses the paper against the blanket 80 that the inked image is transferred to the paper.
In some printing applications, it is desirable that the press be capable of applying a protective and/or decorativ- coating over al1 or a portion of the surface of 2 ~ 7 ::
the printed sheets. Conventional coating liquids include varnish, lacquer, dye and adhesives. Some coating~ are ` formed of a W -curable or wa~er-soluble resin applied as a liquid solution or emulsion via an applicator roller and coating blanket over the freshly printed sheets to protect the ink from set-off or offset and improve the appearance of the sheets. The use of such coatings is particularly desirable when glossy, decorative or protective finishes are required such as in the production of posters, record jackets, brochures, magazines, folding cartons, labels and the like.
:
In press jobs where a liquid coating is to be `! applied, the coating operation is performed after the final ~~ ink printing has been completed, preferably by an in-line : . : -coater. Conventional coating apparatus which is operable ' as an in-line press operation utilizes an engraved applica-tor roller, with the liquid coating being supplied to the ;, - -`~ engraved roller by means of a doctor blade assembly.
Liquid coating material picked up by the engraved applica-~`~ 20 tor roller is transferred to a coating blanket cylinder for subsequent application to a printed sheet.
` Conventional blankets have a pliable surface made of a material such as nitrile rubber which is receptive to and wettable by ink and/or liquid coating material. Such blanket materials are said to have a high affinity for the liquid coating media. Those high affinity materials have `~ exhibited some retention and/or absorption, and did not '~
. . ~
% ~ 7 LOW AFFINITY COATING BLANKET
FOR ROTARY OFFSET PRESSES
This invention relates generally to sheet-fed or web-fed, rotary offset or flexographic printing presses, and more particularly to an improved coating blanket for the application of protective and/or decorative coatings to the printed surface of freshly printed sheets or web stock.
In rotary offset printing, an image which is to be reproduced on a sheet of paper or some other print stock is formed on a printing plate which is attached to the surface of a rotatable plate cylinder. The image is not printed directly from the plate onto the paper, but is first transferred to an intermediate ink transfer blanket, which is mounted on a rotatable blanket cylinder. The blanket transfers (offsets) the inked image to a sheet of paper which is fed through the nip between a rotatable impression cylinder and the blanket cylinder. The ofPset printing press thus includes a plate cylinder which carrieæ
the printing image, a blanket cylinder which has an ink transfer surface for receiving the inked image, and an impression cylinder which presses the paper against the blanket 80 that the inked image is transferred to the paper.
In some printing applications, it is desirable that the press be capable of applying a protective and/or decorativ- coating over al1 or a portion of the surface of 2 ~ 7 ::
the printed sheets. Conventional coating liquids include varnish, lacquer, dye and adhesives. Some coating~ are ` formed of a W -curable or wa~er-soluble resin applied as a liquid solution or emulsion via an applicator roller and coating blanket over the freshly printed sheets to protect the ink from set-off or offset and improve the appearance of the sheets. The use of such coatings is particularly desirable when glossy, decorative or protective finishes are required such as in the production of posters, record jackets, brochures, magazines, folding cartons, labels and the like.
:
In press jobs where a liquid coating is to be `! applied, the coating operation is performed after the final ~~ ink printing has been completed, preferably by an in-line : . : -coater. Conventional coating apparatus which is operable ' as an in-line press operation utilizes an engraved applica-tor roller, with the liquid coating being supplied to the ;, - -`~ engraved roller by means of a doctor blade assembly.
Liquid coating material picked up by the engraved applica-~`~ 20 tor roller is transferred to a coating blanket cylinder for subsequent application to a printed sheet.
` Conventional blankets have a pliable surface made of a material such as nitrile rubber which is receptive to and wettable by ink and/or liquid coating material. Such blanket materials are said to have a high affinity for the liquid coating media. Those high affinity materials have `~ exhibited some retention and/or absorption, and did not '~
. . ~
provide a clean release of the liquid transfer media to a receptor media (paper sheet) without retaining an unaccept-able ink trace on the blanket surface, known in the trade as "back-trapping".
5Conventional coating blankets having a base layer of durable, flexible material, for example, woven fabrics or reinforced paper, and may include one or more intermedi~
ate compressible layers, typically of soft rubber, and an outer transfer layer, typically of vulcanized nitrile rubber, which has a high affinity for liquid coating materials and/or ink. The outer transfer layer i6 secured by adhesive bonding to the intermediate compressible layer.
The nitrile rubber layer is hardened by vulcanizing and its transfer surface is finished by calendaring, grinding or ~ ~;
~illing the hardened rubber in successively thin layers until a desired thickness is obtained. ;~
Photopolymer materials are used in the construc~
tion of conventional coating blankets and are available from E.I. DuPont de Nemours & Company of Wilmington, Delaware under its registered trademark CYREL. The CYREL
photopolymer blankets have a photoæensitive elastomeric layer of solvent-soluble, thermoplastic elastomeric composition which, upon exposure to actinic light, forms a solvent-insoluble, elastomeric relief body. In the production of such blankets, a transfer body having a uniform coating surface is produced by exposing the photosensitive layer through an image-bearing transparency.
: - :
5Conventional coating blankets having a base layer of durable, flexible material, for example, woven fabrics or reinforced paper, and may include one or more intermedi~
ate compressible layers, typically of soft rubber, and an outer transfer layer, typically of vulcanized nitrile rubber, which has a high affinity for liquid coating materials and/or ink. The outer transfer layer i6 secured by adhesive bonding to the intermediate compressible layer.
The nitrile rubber layer is hardened by vulcanizing and its transfer surface is finished by calendaring, grinding or ~ ~;
~illing the hardened rubber in successively thin layers until a desired thickness is obtained. ;~
Photopolymer materials are used in the construc~
tion of conventional coating blankets and are available from E.I. DuPont de Nemours & Company of Wilmington, Delaware under its registered trademark CYREL. The CYREL
photopolymer blankets have a photoæensitive elastomeric layer of solvent-soluble, thermoplastic elastomeric composition which, upon exposure to actinic light, forms a solvent-insoluble, elastomeric relief body. In the production of such blankets, a transfer body having a uniform coating surface is produced by exposing the photosensitive layer through an image-bearing transparency.
: - :
The photosensitive layer typically includea an addit$on-polymerizable, ethylenically unsaturated compound or mixture of compounds, a solvent-soluble elastomeric binder, and a dispersion of an addition-polymerization initiator activatable by actinic light.
Removal of the layer in nonexposed areas, for example by treatment with a suitable solvent, leaves a coating relief surface. Such flexographic coating blankets are not as elastomeric as the molded rubber blankets.
Moreover, the photosensitive elements tend to cold flow due to high monomer concentrations, and do not have the desired ~-features of vulcanized rubber without reducing solvent -solubility as well. Such photopolymer coating blankets also generally possess tacky ~urfaces which lead to picking 15 and tearing of paper during coating. The printed image ;~
elements are blurred by picked-up paper fibers. The photopolymer materials may be treated, for example with bromine, iodine or chlorine solutions, to reduce tackiness, but the photopolymer blanket surface will become tacky 20 again during long coating runs. The after-treatment of ~ ~
photopolymer surfaces to reduce tackiness destroys the ~-smooth, uniform surface on the coating blanket which further interferes with smooth coating performance.
Finally, such photopolymer blankets are not flexible enough 25 to be used in combination with packing sheets for accommo- I
dating spot coating. The blanket must be custom made for each particular spot coating application.
' ,,," ~ , , , , . . , , ' ',: . ' ' ' . ' . '. i ' .,: . ' ` ! ' . . ' ~ n ~ ~ ~ 7 ~ _5_ ; :- . ~
7'~ A problem experienced by press operators in r.~ connection with such conventional coating blankets is the "...................................................................... ~ ~ , ~ accumulation of ink traces on the blanket surface, so that ~: , splitting of the image occurs. A partial or ghost image y 5 may appear on the next advancing sheet, producing what i6 ~l . .
known in the trade as offset image, sometimes referred to - ~
as "back-trapping". Accumulation of ink or hardened i~ ;
coating material on the coating blanket transfer surface will inhibit the pick-up of liquid coating material from -~
10 the applicator roller. Consequently, the finish will be dull, and the colors muddy.
; Another problem which has been observed, particu-larly at high press speeds, is the sticking or slow release of the sheets from the coating blanket cylinder. Sticking 15 or slow release may cause a sheet of paper to adhere to the blanket, requiring shut down of the press so that the sheet can be cleared. If such sticking/slow release should cause -~
multiple sheets to jam the nip, the coating blanket may be damaged beyond repair and must be replaced.
When back-trapping occurs, the press must be stopped so that the coating blanket transfer surface may be .;
`1 washed clean. Some coating blankets may be cleaned only by j special cleaning chemicals which may be toxic, acidic or ;~ caustic, and may cause personal injury to press personnel.
25 Moreover, such chemical solutions may attack the blanket i~ ;
and eat away its transfer surface.
According to the present invention, a coating ?~' ~
`' :-' ' ~'~ :' ' -blanket is provided in which the transfer surface of the blanket has a relatively low affinity for the liquid coating material or ink, rather than a high affinity material such as vulcanized rubber of the kind used in conventional blanket construction. This is accomplished by a coating blanket assembly having a dimensionally stable carrier sheet which supports a transfer layer of a non-tacky, low affinity material, for example a fluorinated polymer resin such as polytetrafluoro-ethylene or a silicone elastomer resin, such as trichloromethyl-silane copolymerized with difunctional silane.
Such materials have a low affinity for the liquid transfer media, such as liquid coating material or liquid printing ink, so that the coating material or ink will not adhere to the coating blanket surface, and will instead be released and transferred to the printed sheets. The coating blanket material is considered to have a low affinity for a given liquid media if it will cleanly release the liquid media to a receptor media eubstantially without retaining residue. That is, the low affinity transfer material is characterized by its ability to resist wetting by the liquid coating media, and has a tendency to form a non-spreading bead or droplet of the liquid coating media on the transfer media surface. The adhesive inter-face attraction of coating to the blanket is less than theadhesive interface attraction of the coating to the paper.
Thus, most of the coating material is transferred to the , ~:
2~ 7 ~ ~ ~
paper, and only a ~race amount of coa~ing remains on the blanket transfer surface.
Operational features and advantages of the present invention will be understood by those skilled in the art upon reading the detailed description which follows with reference to the attached drawings, wherein:
FIGURE 1 is a simplified, schematic diagram . showing the relative positions of the principal components of a rotary offset printing press, with the coating blanket of the present invention being used for applying a protec-tive coating to a freshly printed sheet;
FIGURE 2 is a fragmentary, greatly enlarged, sectional view of a coating blanket having a dimensionally stable carrier sheet on which a transfer layer of non-tacky, low affinity material is bonded;
FIGURE 3 is a perspectiv~ view, partially in section and partially broken away, showing the installation :. of the coating blanket of Figure 2 on a coating blanket cylinder;
FIGURE 4 is a perspective view, partially in section, of a compressible blanket embodiment of the present invention;
FIGURE 5 is a sectional view, partially broken away, of the compressible blanket of FIGURE 4 installed on a coating blanket cylinder;
FIGURE 6 is a schematic side elevational view in which the coating blanket of the present invention is being ~ : - :::
~ ~1 n~3ll7 --pi ~
used for offset coating material transfer in a four color offset rotary printing press;
FIGURE 7 is an enlarged fragmentary side eleva~
tional view taken substantially within the circular area designated "7" of FIGURE 6 and showing the coating blankst of the present invention as used in an in-line coating operation;
FIGURE 8 is a perspective view, partially in section, of a laminated coating blanket embodiment of the present invention; and, FIGURE 9 is a fragmentary, greatly enlarged, sectional view of a coating blanket having a dimensionally stable carrier sheet on which a composite transfer layer is adhesively bonded.
In the description which follows, like parts are indicated throughout the specification and drawings with :` .
the same reference numerals, respectively. The drawings are not neces-sarily to scale and the proportions of certain parts have been exaggerated to better illustrate . I . .
details of the present invention.
The improved coating blanket 10 of the present ! invention will now be described as used generally in a rotary offset printing press. Referring now to FIGURE 1, ~ FIGURE 2 and FIGURE 3, the coating blanket 10 is mounted on `I ..
a coating blanket cylinder 12 in a rotary offset printing press 14. The offset printing press 14 includes a plate cylinder 16, an ink transfer blanket cylinder 1~, and an i:~
r~
~ 1 n ~ ~ ~ 7 _9~
impression cylinder 20. Mounted on the plate cylinder 16 is a metal plate 22 (either zinc or aluminum) which has been given a sensitized coating on which an image has been ;formed by a photographic process. A cluster 24 of moisten-,5 ing or dampening rollers applies a thin film of dampening :liquid to the printing plate 22, which then comes into contact with a cluster 26 of inking rollers. The ink i8 reject d by the hydrophillic non-image holding areas of the printing plate 22, but i8 absorbed by the ink receptive (oleophillic) surface areas of the image.
Referring to Figure 2, the coating blanket 10 has a low affinity transfer layer 28 which receives the liquid coating material from an applicator roller 30 and transfer the coating to a freshly printed sheet S of paper. The printed sheet S is fed through the nip N between the impression cylinder 20 and the coating blanket cylinder 12.
~, As the impression cylinder 20 presses the sheet against the coating blanket 10, liquid coating material is transferred to the sheet.
,. :
That is, the sheet S is fed between the coating l blanket cylinder 12 and the impression cylinder 20 and `~ receives the liquid coating material directly from the coating blanket 10 to provide a decorative and/or protec~
~ tive coating on the freshly printed sheet. The pressure `'25 applied by the applicator roller 30 to the coating blanket cylinder 12 is adjustable to obtain a uniform transfer of liquid coating material, without crushing or otherwise . :: .,:
~ :.
deforming the coating blanket 10.
Referring again to FIGURE 2, the blanket assembly 10 includes a base carrier layer 32 made of a durable, dimensionally stable and flexible material, for example a sheet of MYLAR polyester film. Flexible materials other than MYLAR polyester film may be used to good advantage f'or forming the base carrier sheet 32. For example, metallic sheet materials such as stainless steel, aluminum and copper may also be used. The carrier sheet gauge thickness should be sufficient to provide strength and dimensional stability and yet be flexible enough to easily wrap about the coating blanket cylinder 12. Generally, gauge thick-nesses in the range of about 2 mils to about 8 mils, preferably about 4 mils, are satisfactory.
Referring to Figure 3, the coating blanket 10 has a trailing end portion 10A which is terminated by a clamp plate 34. The leading end 10B of the coating blanket assembly 10 is secured within an elongated slot of a ` ratchet wheel 36. One or more packing sheets 38 are sandwiched between the base carrier sheet 32 and the i~ external surface of the coating blanket cylinder 12 as shown in Figure 3. The packing sheets 38 raise the coating ~j blanket surface over a localized relief area corresponding ;~ to the surface of the printed sheet which is to be coated.
~i 25 The packing sheets 38 and the coating blanXet 10 are '~3i assembled onto the blanket cylinder 12 by first attaching the clamp plate 34 onto the coating blanket cylinder 12 '',`
.~
.
. j .
, . .
within a channel pocket 40. The clamp plate 34 is secured by threaded fasten~r bolts 42, and the ratchet wheel 36 i8 secured by a ratchet clamp (not shown). After the coating blanket 10 has been secured in place, with the packing sheets 38 confined between the coating blanket 10 and the coating blanket cylinder 12, the ratchet wheel 36 is tightened to secure the coating blanket 10 in tension about the coating blanket cylinder 12.
Referring now to FIGURE 4, a compressible blanket assembly 100 is illustrated. To avoid crushing, denting or otherwise deforming the hard, low affinity transfer layer 28, the transfer layer 28 is supported by a resilient intermediate layer 44 of soft, compressible rubber. The base carrier sheet 32 and the intermediate compressible layer 44 are stabilized and secured together by an adhesive deposit 46. The low affinity transfer layer 28 is prefera~
bly formed and secured to the compressible layer 44 by adhesively bonding a sheet of a low affinity material such as a fluorinated polymer resin, for example TEFLON PTFE or ~'` 20 FEP film, or a silicone elastomer. The transfer layer 28 : ~
may also be formed and secured by spray coating, bulk ' forming and hot melt extrusion.
Referring to FIGURE 5, the compressible blanket , . , .:
assembly 100 is secured about the coating cylinder 12 as previously described in connection with the coating blanket .: .: .
`, 10.
Referring now to FIGURE 6 and FIGURE 7, the .- ~
~ 2 1 ~ 7 coating blanket 10 of the present ~nvention will now be ~ described as used for applying a protective and/or decora-; tive coating to the freshly printed surface of sheets printed in a sheet-fed or web-fed, offset rotary or flexographic printing press, herein generally designated 50. In this instance, as shown in FIGURE 6, the coating blanket 10 of the present invention is mounted on a delivery/transfer cylinder 12 in a four color printing press, such as that manufactured by Heidelberg Druckmaschinen AG of Germany under its designation Heidel-berg Speedmaster 102V. The press 50 includes a press frame 54 coupled at one end, herein the right end, with a sheet feeder 56 from which sheets, herein designated S, are individually and sequentially fed into the press, and at the opposite end, with a sheet delivery stacker 58 in which ;t~ the finally printed sheets are collected and stacked.
r~l Interposed between the sheet feeder and the sheet delivery f, stacker are four substantially identical sheet printing ;l units 60, 62, 64 and 66 which can print different color .i 20 inks onto the sheets as they are moved through the press 50.
As illustrated, the printing units are substan-tially identical and of conventional design, herein , including a sheet-fed cylinder 68, a plate cylinder 16, an ink blanket cylinder 18 and an impression cylinder 20, with ; each of the first three printing units having a transfer cylinder 70 disposed to withdraw the freshly printed sheets ,l .
~``.
2 1 ~ 7 -13~
from the adjacent impression cylinder 20 and transfer the freshly printed sheets to the next printing unit via an interstation transfer cylinder 72. The final printing unit 66 herein is shown as equipped with a delivery/transfer ~; 5 coating cylinder 12 mounted on a delivery drive shaft 74.
The deliver/transfer coating cylinder 12 also support~ the printed sheet S as it is moved from the final impression cylinder by a delivery conveyor system, generally designat~
ed 76, to the sheet delivery stacker 58.
: 10The delivery conveyor system 76 as shown in FIGURE 6 is of conventional design and includes a pair of : endless delivery gripper chains 78, only one of which is shown carrying laterally disposed gripper bars having ~` ~ripper elements G used to grip the leading edge E of a sheet S after it leaves the nip N between the delivery coating cylinder 12 and impression cylinder 20 of the final ~i~printing unit 66. As the leading edge E of the sheet S is gripped by the grippers, the delivery chains pull the sheet ~-~S away from the coating blanket cylinder 12 and convey the freshly printed and coated sheets to the sheet delivery stacker 58.
~;~An in-line doctor blade coating apparatus 80 is provided for applying a protective or decorative coating or ink to the printed sheets S. This in-line coating arrange-ment enables the press to be operated in the normal manner without the loss of the final printing unit, and without ~`~requiring any press modifications, by employing the J ~ 4 7 existing pre~s delivery drive shaft 74 as the mounting location for a delivery tran~fer cylinder 12 on which the liquid material coating blanket 10 of the present invention is mounted. In presses having delivery systems such as skeleton wheels mounted on the delivery drive shaft, conversion to a coating operation may be quickly and easily accomplished by mounting on the press delivery drive æhaft 74 in place of the skeleton wheels, a coating blanket equipped delivery cylinder 12 capable of performing a blanket coating function as well as the delivery transfer function. By utilizing a coating blanket 10 on the delivery/transfer cylinder 12 to also act as a coating blanket cylinder, protective coating may be applied to the printed sheets S in precise timed registration, and will permit the press to be operated with its full complement of printing units.
The coating apparatus 80 includes a relatively simple, positive acting and economical doctor blade coating unit 82, mounted to the press frame 54 downstream of the delivery drive shaft 74 and positioned to apply liquid r~ coating material to the coating blanket 10 mounted on the delivery coating cylinder 12 which is secured to the delivery drive shaft. As shown in FIGURE 7, the doctor blade coating unit 82 includes a pair of side frames 84, only one of which is shown, it being understood that the other side frame is substantially the same as that of the ~ide frame illustrated, attached to the opposite side of .
2~.~23~7 ~ ~
-15~
the press frame. Pivotally mounted to one end of each of the side frames is a support bracket 86 carrying one end of a doctor blade reservoir 88 and a cooperating liquid material applicator roller 30, each disposed to extend ~ :
laterally across the pre~s parallel with the de~
livery/transfer coating cylinder 12. The coating unit 82 i8 mounted between the upper and lower upport rails of the delivery chains downstream of the delivery coating cylinder 12, and positioned so that the outer peripheral surface of the applicator roller 30 can be engaged against the coating blanket 10 on the delivery coating cylinder 12 mounted on the delivery drive shaft 74. - ;
As shown in FIGURE 7, the support bracket ~6 is ~ :
pivotally attached to the end of the side frame 54 by a stub shaft 90 disposed at the lower end portion of the bracket, and can be pivoted about the shaft by an extensi~
ble cylinder 92, herein shown as a pneumatic cylinder, one end of which is secured to the side frame, and the opposite end of which is coupled through a pivot shaft 94 to the . 20 upper end portion of the bracket 86. By extending or :~
retracting the applicator roller 30, the engagement : pressure of the applicator roller 30 against the coating . blanket surface may be controlled, and the applicator `~ roller 30 may be completely disengaged from the transfer ~ `I
coating blanket 10 in a non-operative, idle position.
The coating applicator roller 30, which is of :~
conventional design and preferably having an engraved -. -.
., ( .
. ,~ . : ~ ~ . .
2 ~ ~2~7 ~ ~
ceramic or chrome transfer surface, is designed to pick up a predetermined volume of liquid coating material or ink from the doctor reservoir, and then uniformly transfer the liquid coating material to the coating blanket 10 on the delivery~transfer coating blanket cylinder 12. To effect rotation of the applicator roller, a drive motor 96, either hydraulic or electric, is attachQd to one of the side frames and coupled to a source of power (not shown) through charge and return fittings.
10In the practice of either blanket embodiment of the invention, a preferred fluorinated polymer material for making the transfer layer 28 is polytetrafluoroethylene (PTFE) fluorocarbon polymer resin, or fluorinated ethylene propylene (FEP) resin, both sold by DuPont under its trademark TEFLON. Those materials are curable to a hard, .,!, smooth transfer surface, resist abrasion and deformation, and are characterized by a low surface coefficient of friction and a low affinity for liquid coating materials and/or ink. They are also non-reactive to press room chemicals.
Fluorinated, curable polymers which are useful in this invention contain at least about 37 percent by weight of carbon-bonded fluorine and preferably wherein at least ~, about 50 percent of the non-skeletal carbon valence bonds are fluorine. Exemplary of such polymers are fluorosili-i cone polymers which are generally known as perfluoro alkyl alkylene siloxanes. Those polymers contain a terminal .,, ~
--`` 2~23~7 : ~
perfluoro alkyl group which is positioned no closer than two carbon atoms from the silicone atom, and additionally contain a minor amount of substituent groups which will allow curing or crosslinking to occur. These substituent groups may be, for example, silicone-bonded hydrogen atoms, vinyl groups or peroxy-activatable ~roups. A preferred curable fluorosiliconepolymer, trifluoropropylmethylvinyl polysiloxane, is commercially available from the Dow Corning Company under the trade name LS-53.
The low affinity blanket transfer layer 28 should generally have a thickness in the range of from about 1 mil to about 5 mils, and preferably about 2 mils. The hardness of the transfer layer should be sufficient to provide uniform nip contact area during the coating transfer operation and maintain physical integrity. Generally, fluorinated elastomers having a Shore A durometer hardness ~` of 20-80, preferably about 50, are satisfactory.
The low affinity layer 28 may be conveniently formed by curing the fluorinated polymers in situ at the ~; 20 time of manufacture of the blanket. Curing or crosslinking agents for curing fluorinated polymers are generally well known in the art. Curing conditions vary depending upon the curable fluorinated polymer and curinq agent utilized, with effective cures being obtained at temperatures up to about 450F (232.2C) for a period of from about one minute to about fifteen hours, and more usually from about five minutes to about thirty minutes.
.. : ........... . . . .......... .. .
...... . .
2 1 0 '~ 7 Exemplary silicone elastomers include the cured or further polymerized product of a silicone gum, such as dimethyl vinyl polysiloxane. Preferably, the gum i5 mixed with a silicone resin with equal parts by weight of the gum and resin. However, other proportions of these ingredient~
are al60 useful.
The low affinity transfer layer 28 should have sufficient thickness to permit adequate wear life in term~
of abrasion resistance. The hardness of the blanket transfer l~yer should allow sufficient elongation without tensile failure. A silicone elastomer having about 30 to about 70 Shore A durometer and preferably about 50 Shore A
durometer is satisfactory.
'.~
In the manufacture of the blanket assemblies 10 15 or 100 of this invention, the base carrier sheet 32 and the !~1 compressible intermediate layer 44 should be primed with a i suitable primer for fluorinated elastomers to assure a compatible bond surface and to ensure reliable repeatabili-ty of bond strength. Catalyzed fluorinated polymer may `~ 20 then be applied to the primed surface by conventional means .! 1 such as calendaring, bulk loading, or by spraying to form a low affinity layer 28 having the desired uniform thick-ness. The blanket assembly may then be inserted into a mold and cured at from about 200F (93.3C) to about 400F
25 (204.4C) under a pressure of about 350 psi (246,085 kgs/sq.m).
Referring now to FIGURE 8, a laminated blanket : ~' 2 ~ 3 ~ 7 :::
-19~
assembly 150 is illustrated. In this embodiment, the base carrier layer 32 is a sheet of MYLAR polyester film having a gauge thickness of about 4 mils. The coating transfer layer i6 a sheet of TEFLON fluorinated ethylene propylene copolymer (FEP) film having a gauge thickness of 2 mils.
The TEFLON FEP film layer 28 is laminated onto the MYLAR
carrier sheet 32 by an adhesive deposit 46. The laminated blanket assembly 150 is characterized by impact and scratch resistance, and high flexibility for providing sharp relief edges and high definition when used in combination with packing sheets for spot coating applications.
Referring now to FIGURE 9, a printing blanket 200 has an ink transfer layer 98 which is a composite mixture of a high affinity component and a low affinity component.
The high affinity component is nitrile rubber, which is receptive to and has a relatively high affinity for printing ink, and the low affinity component is a fluori-!
nated polymer resin such as polytetrafluoroethylene (PTFE),or fluorinated ethylene propylene (FEP) resin, or a silicone elastomer resin. The high affinity component ~, provides good ink pick-up, and the low affinity component provides good release. Consequently, the composite layer 98 is a compromise between a conventional nitrile rubber blanket and the low affinity coating blanket embodiments 25 10, 100 and 150 described above. The transfer layer 98 of the ink blanket assembly 200 will accept some ink, yet will , readily release the printed sheet quickly and smoothly.
v ~ 2 ~ ~ ~
The printing blanket 200 is primarily intended for ink transfer applications, and i6 illustrated attached to the ink blanket cylinder 18 in FIGURE 1.
The composite transfer layer 98 may be manufac-tured as a hot melt film extrusion in which pellets o~nitrile rubber are mixed with pellets of a 14w affinity material, for example TEFLON PTFE or TEFLON FEP in various proportions. A dry blend of nitril rubber pellets and elastomer pellets are separately metered into a twin-screw extruder equipped with a filter and sheeting dye. Various proportions of the nitrile rubber to the low affinity material may be employed, with the nitrile rubber component being dominant for ink transfer applications.
It will be apparent that the low affinity coating blanket of the present invention provides significant advantages with respect to conventional coating bla~kets.
The low affinity coating blanket embodiment is less expensive to manufacture as compared to conventional, vulcanized nitrile rubber coating blankets. The embodi-ments which utilize a fluorinated polymer or a siliconeelastomer are more durable and resist scratch~
ing/deformation more effectively than conventional vulca~
nized rubber blankets. Because of the low affinity and non-tacky surface of such materials, the printed sheets are released smoothly, quickly and easily from the nip between the coating blanket cylinder and the impression cylinder, even at high speed operation. Coating blankets made of ,.,., ~ .. : . .. .... . .
2 ~ 3 ~ 7 such low affinity materials are sufficiently flexible to be used in combination with packing sheets of different 6izes to provide for uniform coating over designated localized areas of the printed sheets. The low affinity blanket is also resistant to chemical attack, and may be washed and cleaned with any available press room chemical solutions.
Since the low affinity blanket surface refuses the accumu~
lation of ink and/or coating material, split images, ghost images, offset images and back-trapping defects are eliminated. Because liquid coating material will not permanently adhere to the low affinity blanket surface, ~ ~-hardened coating residue may be easily peeled away or stripped clean from the coating blanket transfer surface with a soft cloth, without scraping or applying a reactive chemical solution.
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Removal of the layer in nonexposed areas, for example by treatment with a suitable solvent, leaves a coating relief surface. Such flexographic coating blankets are not as elastomeric as the molded rubber blankets.
Moreover, the photosensitive elements tend to cold flow due to high monomer concentrations, and do not have the desired ~-features of vulcanized rubber without reducing solvent -solubility as well. Such photopolymer coating blankets also generally possess tacky ~urfaces which lead to picking 15 and tearing of paper during coating. The printed image ;~
elements are blurred by picked-up paper fibers. The photopolymer materials may be treated, for example with bromine, iodine or chlorine solutions, to reduce tackiness, but the photopolymer blanket surface will become tacky 20 again during long coating runs. The after-treatment of ~ ~
photopolymer surfaces to reduce tackiness destroys the ~-smooth, uniform surface on the coating blanket which further interferes with smooth coating performance.
Finally, such photopolymer blankets are not flexible enough 25 to be used in combination with packing sheets for accommo- I
dating spot coating. The blanket must be custom made for each particular spot coating application.
' ,,," ~ , , , , . . , , ' ',: . ' ' ' . ' . '. i ' .,: . ' ` ! ' . . ' ~ n ~ ~ ~ 7 ~ _5_ ; :- . ~
7'~ A problem experienced by press operators in r.~ connection with such conventional coating blankets is the "...................................................................... ~ ~ , ~ accumulation of ink traces on the blanket surface, so that ~: , splitting of the image occurs. A partial or ghost image y 5 may appear on the next advancing sheet, producing what i6 ~l . .
known in the trade as offset image, sometimes referred to - ~
as "back-trapping". Accumulation of ink or hardened i~ ;
coating material on the coating blanket transfer surface will inhibit the pick-up of liquid coating material from -~
10 the applicator roller. Consequently, the finish will be dull, and the colors muddy.
; Another problem which has been observed, particu-larly at high press speeds, is the sticking or slow release of the sheets from the coating blanket cylinder. Sticking 15 or slow release may cause a sheet of paper to adhere to the blanket, requiring shut down of the press so that the sheet can be cleared. If such sticking/slow release should cause -~
multiple sheets to jam the nip, the coating blanket may be damaged beyond repair and must be replaced.
When back-trapping occurs, the press must be stopped so that the coating blanket transfer surface may be .;
`1 washed clean. Some coating blankets may be cleaned only by j special cleaning chemicals which may be toxic, acidic or ;~ caustic, and may cause personal injury to press personnel.
25 Moreover, such chemical solutions may attack the blanket i~ ;
and eat away its transfer surface.
According to the present invention, a coating ?~' ~
`' :-' ' ~'~ :' ' -blanket is provided in which the transfer surface of the blanket has a relatively low affinity for the liquid coating material or ink, rather than a high affinity material such as vulcanized rubber of the kind used in conventional blanket construction. This is accomplished by a coating blanket assembly having a dimensionally stable carrier sheet which supports a transfer layer of a non-tacky, low affinity material, for example a fluorinated polymer resin such as polytetrafluoro-ethylene or a silicone elastomer resin, such as trichloromethyl-silane copolymerized with difunctional silane.
Such materials have a low affinity for the liquid transfer media, such as liquid coating material or liquid printing ink, so that the coating material or ink will not adhere to the coating blanket surface, and will instead be released and transferred to the printed sheets. The coating blanket material is considered to have a low affinity for a given liquid media if it will cleanly release the liquid media to a receptor media eubstantially without retaining residue. That is, the low affinity transfer material is characterized by its ability to resist wetting by the liquid coating media, and has a tendency to form a non-spreading bead or droplet of the liquid coating media on the transfer media surface. The adhesive inter-face attraction of coating to the blanket is less than theadhesive interface attraction of the coating to the paper.
Thus, most of the coating material is transferred to the , ~:
2~ 7 ~ ~ ~
paper, and only a ~race amount of coa~ing remains on the blanket transfer surface.
Operational features and advantages of the present invention will be understood by those skilled in the art upon reading the detailed description which follows with reference to the attached drawings, wherein:
FIGURE 1 is a simplified, schematic diagram . showing the relative positions of the principal components of a rotary offset printing press, with the coating blanket of the present invention being used for applying a protec-tive coating to a freshly printed sheet;
FIGURE 2 is a fragmentary, greatly enlarged, sectional view of a coating blanket having a dimensionally stable carrier sheet on which a transfer layer of non-tacky, low affinity material is bonded;
FIGURE 3 is a perspectiv~ view, partially in section and partially broken away, showing the installation :. of the coating blanket of Figure 2 on a coating blanket cylinder;
FIGURE 4 is a perspective view, partially in section, of a compressible blanket embodiment of the present invention;
FIGURE 5 is a sectional view, partially broken away, of the compressible blanket of FIGURE 4 installed on a coating blanket cylinder;
FIGURE 6 is a schematic side elevational view in which the coating blanket of the present invention is being ~ : - :::
~ ~1 n~3ll7 --pi ~
used for offset coating material transfer in a four color offset rotary printing press;
FIGURE 7 is an enlarged fragmentary side eleva~
tional view taken substantially within the circular area designated "7" of FIGURE 6 and showing the coating blankst of the present invention as used in an in-line coating operation;
FIGURE 8 is a perspective view, partially in section, of a laminated coating blanket embodiment of the present invention; and, FIGURE 9 is a fragmentary, greatly enlarged, sectional view of a coating blanket having a dimensionally stable carrier sheet on which a composite transfer layer is adhesively bonded.
In the description which follows, like parts are indicated throughout the specification and drawings with :` .
the same reference numerals, respectively. The drawings are not neces-sarily to scale and the proportions of certain parts have been exaggerated to better illustrate . I . .
details of the present invention.
The improved coating blanket 10 of the present ! invention will now be described as used generally in a rotary offset printing press. Referring now to FIGURE 1, ~ FIGURE 2 and FIGURE 3, the coating blanket 10 is mounted on `I ..
a coating blanket cylinder 12 in a rotary offset printing press 14. The offset printing press 14 includes a plate cylinder 16, an ink transfer blanket cylinder 1~, and an i:~
r~
~ 1 n ~ ~ ~ 7 _9~
impression cylinder 20. Mounted on the plate cylinder 16 is a metal plate 22 (either zinc or aluminum) which has been given a sensitized coating on which an image has been ;formed by a photographic process. A cluster 24 of moisten-,5 ing or dampening rollers applies a thin film of dampening :liquid to the printing plate 22, which then comes into contact with a cluster 26 of inking rollers. The ink i8 reject d by the hydrophillic non-image holding areas of the printing plate 22, but i8 absorbed by the ink receptive (oleophillic) surface areas of the image.
Referring to Figure 2, the coating blanket 10 has a low affinity transfer layer 28 which receives the liquid coating material from an applicator roller 30 and transfer the coating to a freshly printed sheet S of paper. The printed sheet S is fed through the nip N between the impression cylinder 20 and the coating blanket cylinder 12.
~, As the impression cylinder 20 presses the sheet against the coating blanket 10, liquid coating material is transferred to the sheet.
,. :
That is, the sheet S is fed between the coating l blanket cylinder 12 and the impression cylinder 20 and `~ receives the liquid coating material directly from the coating blanket 10 to provide a decorative and/or protec~
~ tive coating on the freshly printed sheet. The pressure `'25 applied by the applicator roller 30 to the coating blanket cylinder 12 is adjustable to obtain a uniform transfer of liquid coating material, without crushing or otherwise . :: .,:
~ :.
deforming the coating blanket 10.
Referring again to FIGURE 2, the blanket assembly 10 includes a base carrier layer 32 made of a durable, dimensionally stable and flexible material, for example a sheet of MYLAR polyester film. Flexible materials other than MYLAR polyester film may be used to good advantage f'or forming the base carrier sheet 32. For example, metallic sheet materials such as stainless steel, aluminum and copper may also be used. The carrier sheet gauge thickness should be sufficient to provide strength and dimensional stability and yet be flexible enough to easily wrap about the coating blanket cylinder 12. Generally, gauge thick-nesses in the range of about 2 mils to about 8 mils, preferably about 4 mils, are satisfactory.
Referring to Figure 3, the coating blanket 10 has a trailing end portion 10A which is terminated by a clamp plate 34. The leading end 10B of the coating blanket assembly 10 is secured within an elongated slot of a ` ratchet wheel 36. One or more packing sheets 38 are sandwiched between the base carrier sheet 32 and the i~ external surface of the coating blanket cylinder 12 as shown in Figure 3. The packing sheets 38 raise the coating ~j blanket surface over a localized relief area corresponding ;~ to the surface of the printed sheet which is to be coated.
~i 25 The packing sheets 38 and the coating blanXet 10 are '~3i assembled onto the blanket cylinder 12 by first attaching the clamp plate 34 onto the coating blanket cylinder 12 '',`
.~
.
. j .
, . .
within a channel pocket 40. The clamp plate 34 is secured by threaded fasten~r bolts 42, and the ratchet wheel 36 i8 secured by a ratchet clamp (not shown). After the coating blanket 10 has been secured in place, with the packing sheets 38 confined between the coating blanket 10 and the coating blanket cylinder 12, the ratchet wheel 36 is tightened to secure the coating blanket 10 in tension about the coating blanket cylinder 12.
Referring now to FIGURE 4, a compressible blanket assembly 100 is illustrated. To avoid crushing, denting or otherwise deforming the hard, low affinity transfer layer 28, the transfer layer 28 is supported by a resilient intermediate layer 44 of soft, compressible rubber. The base carrier sheet 32 and the intermediate compressible layer 44 are stabilized and secured together by an adhesive deposit 46. The low affinity transfer layer 28 is prefera~
bly formed and secured to the compressible layer 44 by adhesively bonding a sheet of a low affinity material such as a fluorinated polymer resin, for example TEFLON PTFE or ~'` 20 FEP film, or a silicone elastomer. The transfer layer 28 : ~
may also be formed and secured by spray coating, bulk ' forming and hot melt extrusion.
Referring to FIGURE 5, the compressible blanket , . , .:
assembly 100 is secured about the coating cylinder 12 as previously described in connection with the coating blanket .: .: .
`, 10.
Referring now to FIGURE 6 and FIGURE 7, the .- ~
~ 2 1 ~ 7 coating blanket 10 of the present ~nvention will now be ~ described as used for applying a protective and/or decora-; tive coating to the freshly printed surface of sheets printed in a sheet-fed or web-fed, offset rotary or flexographic printing press, herein generally designated 50. In this instance, as shown in FIGURE 6, the coating blanket 10 of the present invention is mounted on a delivery/transfer cylinder 12 in a four color printing press, such as that manufactured by Heidelberg Druckmaschinen AG of Germany under its designation Heidel-berg Speedmaster 102V. The press 50 includes a press frame 54 coupled at one end, herein the right end, with a sheet feeder 56 from which sheets, herein designated S, are individually and sequentially fed into the press, and at the opposite end, with a sheet delivery stacker 58 in which ;t~ the finally printed sheets are collected and stacked.
r~l Interposed between the sheet feeder and the sheet delivery f, stacker are four substantially identical sheet printing ;l units 60, 62, 64 and 66 which can print different color .i 20 inks onto the sheets as they are moved through the press 50.
As illustrated, the printing units are substan-tially identical and of conventional design, herein , including a sheet-fed cylinder 68, a plate cylinder 16, an ink blanket cylinder 18 and an impression cylinder 20, with ; each of the first three printing units having a transfer cylinder 70 disposed to withdraw the freshly printed sheets ,l .
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2 1 ~ 7 -13~
from the adjacent impression cylinder 20 and transfer the freshly printed sheets to the next printing unit via an interstation transfer cylinder 72. The final printing unit 66 herein is shown as equipped with a delivery/transfer ~; 5 coating cylinder 12 mounted on a delivery drive shaft 74.
The deliver/transfer coating cylinder 12 also support~ the printed sheet S as it is moved from the final impression cylinder by a delivery conveyor system, generally designat~
ed 76, to the sheet delivery stacker 58.
: 10The delivery conveyor system 76 as shown in FIGURE 6 is of conventional design and includes a pair of : endless delivery gripper chains 78, only one of which is shown carrying laterally disposed gripper bars having ~` ~ripper elements G used to grip the leading edge E of a sheet S after it leaves the nip N between the delivery coating cylinder 12 and impression cylinder 20 of the final ~i~printing unit 66. As the leading edge E of the sheet S is gripped by the grippers, the delivery chains pull the sheet ~-~S away from the coating blanket cylinder 12 and convey the freshly printed and coated sheets to the sheet delivery stacker 58.
~;~An in-line doctor blade coating apparatus 80 is provided for applying a protective or decorative coating or ink to the printed sheets S. This in-line coating arrange-ment enables the press to be operated in the normal manner without the loss of the final printing unit, and without ~`~requiring any press modifications, by employing the J ~ 4 7 existing pre~s delivery drive shaft 74 as the mounting location for a delivery tran~fer cylinder 12 on which the liquid material coating blanket 10 of the present invention is mounted. In presses having delivery systems such as skeleton wheels mounted on the delivery drive shaft, conversion to a coating operation may be quickly and easily accomplished by mounting on the press delivery drive æhaft 74 in place of the skeleton wheels, a coating blanket equipped delivery cylinder 12 capable of performing a blanket coating function as well as the delivery transfer function. By utilizing a coating blanket 10 on the delivery/transfer cylinder 12 to also act as a coating blanket cylinder, protective coating may be applied to the printed sheets S in precise timed registration, and will permit the press to be operated with its full complement of printing units.
The coating apparatus 80 includes a relatively simple, positive acting and economical doctor blade coating unit 82, mounted to the press frame 54 downstream of the delivery drive shaft 74 and positioned to apply liquid r~ coating material to the coating blanket 10 mounted on the delivery coating cylinder 12 which is secured to the delivery drive shaft. As shown in FIGURE 7, the doctor blade coating unit 82 includes a pair of side frames 84, only one of which is shown, it being understood that the other side frame is substantially the same as that of the ~ide frame illustrated, attached to the opposite side of .
2~.~23~7 ~ ~
-15~
the press frame. Pivotally mounted to one end of each of the side frames is a support bracket 86 carrying one end of a doctor blade reservoir 88 and a cooperating liquid material applicator roller 30, each disposed to extend ~ :
laterally across the pre~s parallel with the de~
livery/transfer coating cylinder 12. The coating unit 82 i8 mounted between the upper and lower upport rails of the delivery chains downstream of the delivery coating cylinder 12, and positioned so that the outer peripheral surface of the applicator roller 30 can be engaged against the coating blanket 10 on the delivery coating cylinder 12 mounted on the delivery drive shaft 74. - ;
As shown in FIGURE 7, the support bracket ~6 is ~ :
pivotally attached to the end of the side frame 54 by a stub shaft 90 disposed at the lower end portion of the bracket, and can be pivoted about the shaft by an extensi~
ble cylinder 92, herein shown as a pneumatic cylinder, one end of which is secured to the side frame, and the opposite end of which is coupled through a pivot shaft 94 to the . 20 upper end portion of the bracket 86. By extending or :~
retracting the applicator roller 30, the engagement : pressure of the applicator roller 30 against the coating . blanket surface may be controlled, and the applicator `~ roller 30 may be completely disengaged from the transfer ~ `I
coating blanket 10 in a non-operative, idle position.
The coating applicator roller 30, which is of :~
conventional design and preferably having an engraved -. -.
., ( .
. ,~ . : ~ ~ . .
2 ~ ~2~7 ~ ~
ceramic or chrome transfer surface, is designed to pick up a predetermined volume of liquid coating material or ink from the doctor reservoir, and then uniformly transfer the liquid coating material to the coating blanket 10 on the delivery~transfer coating blanket cylinder 12. To effect rotation of the applicator roller, a drive motor 96, either hydraulic or electric, is attachQd to one of the side frames and coupled to a source of power (not shown) through charge and return fittings.
10In the practice of either blanket embodiment of the invention, a preferred fluorinated polymer material for making the transfer layer 28 is polytetrafluoroethylene (PTFE) fluorocarbon polymer resin, or fluorinated ethylene propylene (FEP) resin, both sold by DuPont under its trademark TEFLON. Those materials are curable to a hard, .,!, smooth transfer surface, resist abrasion and deformation, and are characterized by a low surface coefficient of friction and a low affinity for liquid coating materials and/or ink. They are also non-reactive to press room chemicals.
Fluorinated, curable polymers which are useful in this invention contain at least about 37 percent by weight of carbon-bonded fluorine and preferably wherein at least ~, about 50 percent of the non-skeletal carbon valence bonds are fluorine. Exemplary of such polymers are fluorosili-i cone polymers which are generally known as perfluoro alkyl alkylene siloxanes. Those polymers contain a terminal .,, ~
--`` 2~23~7 : ~
perfluoro alkyl group which is positioned no closer than two carbon atoms from the silicone atom, and additionally contain a minor amount of substituent groups which will allow curing or crosslinking to occur. These substituent groups may be, for example, silicone-bonded hydrogen atoms, vinyl groups or peroxy-activatable ~roups. A preferred curable fluorosiliconepolymer, trifluoropropylmethylvinyl polysiloxane, is commercially available from the Dow Corning Company under the trade name LS-53.
The low affinity blanket transfer layer 28 should generally have a thickness in the range of from about 1 mil to about 5 mils, and preferably about 2 mils. The hardness of the transfer layer should be sufficient to provide uniform nip contact area during the coating transfer operation and maintain physical integrity. Generally, fluorinated elastomers having a Shore A durometer hardness ~` of 20-80, preferably about 50, are satisfactory.
The low affinity layer 28 may be conveniently formed by curing the fluorinated polymers in situ at the ~; 20 time of manufacture of the blanket. Curing or crosslinking agents for curing fluorinated polymers are generally well known in the art. Curing conditions vary depending upon the curable fluorinated polymer and curinq agent utilized, with effective cures being obtained at temperatures up to about 450F (232.2C) for a period of from about one minute to about fifteen hours, and more usually from about five minutes to about thirty minutes.
.. : ........... . . . .......... .. .
...... . .
2 1 0 '~ 7 Exemplary silicone elastomers include the cured or further polymerized product of a silicone gum, such as dimethyl vinyl polysiloxane. Preferably, the gum i5 mixed with a silicone resin with equal parts by weight of the gum and resin. However, other proportions of these ingredient~
are al60 useful.
The low affinity transfer layer 28 should have sufficient thickness to permit adequate wear life in term~
of abrasion resistance. The hardness of the blanket transfer l~yer should allow sufficient elongation without tensile failure. A silicone elastomer having about 30 to about 70 Shore A durometer and preferably about 50 Shore A
durometer is satisfactory.
'.~
In the manufacture of the blanket assemblies 10 15 or 100 of this invention, the base carrier sheet 32 and the !~1 compressible intermediate layer 44 should be primed with a i suitable primer for fluorinated elastomers to assure a compatible bond surface and to ensure reliable repeatabili-ty of bond strength. Catalyzed fluorinated polymer may `~ 20 then be applied to the primed surface by conventional means .! 1 such as calendaring, bulk loading, or by spraying to form a low affinity layer 28 having the desired uniform thick-ness. The blanket assembly may then be inserted into a mold and cured at from about 200F (93.3C) to about 400F
25 (204.4C) under a pressure of about 350 psi (246,085 kgs/sq.m).
Referring now to FIGURE 8, a laminated blanket : ~' 2 ~ 3 ~ 7 :::
-19~
assembly 150 is illustrated. In this embodiment, the base carrier layer 32 is a sheet of MYLAR polyester film having a gauge thickness of about 4 mils. The coating transfer layer i6 a sheet of TEFLON fluorinated ethylene propylene copolymer (FEP) film having a gauge thickness of 2 mils.
The TEFLON FEP film layer 28 is laminated onto the MYLAR
carrier sheet 32 by an adhesive deposit 46. The laminated blanket assembly 150 is characterized by impact and scratch resistance, and high flexibility for providing sharp relief edges and high definition when used in combination with packing sheets for spot coating applications.
Referring now to FIGURE 9, a printing blanket 200 has an ink transfer layer 98 which is a composite mixture of a high affinity component and a low affinity component.
The high affinity component is nitrile rubber, which is receptive to and has a relatively high affinity for printing ink, and the low affinity component is a fluori-!
nated polymer resin such as polytetrafluoroethylene (PTFE),or fluorinated ethylene propylene (FEP) resin, or a silicone elastomer resin. The high affinity component ~, provides good ink pick-up, and the low affinity component provides good release. Consequently, the composite layer 98 is a compromise between a conventional nitrile rubber blanket and the low affinity coating blanket embodiments 25 10, 100 and 150 described above. The transfer layer 98 of the ink blanket assembly 200 will accept some ink, yet will , readily release the printed sheet quickly and smoothly.
v ~ 2 ~ ~ ~
The printing blanket 200 is primarily intended for ink transfer applications, and i6 illustrated attached to the ink blanket cylinder 18 in FIGURE 1.
The composite transfer layer 98 may be manufac-tured as a hot melt film extrusion in which pellets o~nitrile rubber are mixed with pellets of a 14w affinity material, for example TEFLON PTFE or TEFLON FEP in various proportions. A dry blend of nitril rubber pellets and elastomer pellets are separately metered into a twin-screw extruder equipped with a filter and sheeting dye. Various proportions of the nitrile rubber to the low affinity material may be employed, with the nitrile rubber component being dominant for ink transfer applications.
It will be apparent that the low affinity coating blanket of the present invention provides significant advantages with respect to conventional coating bla~kets.
The low affinity coating blanket embodiment is less expensive to manufacture as compared to conventional, vulcanized nitrile rubber coating blankets. The embodi-ments which utilize a fluorinated polymer or a siliconeelastomer are more durable and resist scratch~
ing/deformation more effectively than conventional vulca~
nized rubber blankets. Because of the low affinity and non-tacky surface of such materials, the printed sheets are released smoothly, quickly and easily from the nip between the coating blanket cylinder and the impression cylinder, even at high speed operation. Coating blankets made of ,.,., ~ .. : . .. .... . .
2 ~ 3 ~ 7 such low affinity materials are sufficiently flexible to be used in combination with packing sheets of different 6izes to provide for uniform coating over designated localized areas of the printed sheets. The low affinity blanket is also resistant to chemical attack, and may be washed and cleaned with any available press room chemical solutions.
Since the low affinity blanket surface refuses the accumu~
lation of ink and/or coating material, split images, ghost images, offset images and back-trapping defects are eliminated. Because liquid coating material will not permanently adhere to the low affinity blanket surface, ~ ~-hardened coating residue may be easily peeled away or stripped clean from the coating blanket transfer surface with a soft cloth, without scraping or applying a reactive chemical solution.
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Claims (16)
1. A blanket assembly (10) for attachment to a cylinder (12) in a printing press (14) characterized as follows:
a base carrier sheet (32); and, a liquid media transfer layer (28) supported by the base carrier sheet, the transfer layer being made of a material having a low affinity for the liquid media.
a base carrier sheet (32); and, a liquid media transfer layer (28) supported by the base carrier sheet, the transfer layer being made of a material having a low affinity for the liquid media.
2. A blanket assembly (10) as defined in claim 1, said transfer layer (28) comprising a fluorinated polymer resin.
3. A blanket assembly (10) as defined in claim 2, wherein the fluorinated polymer resin comprises tetra-fluoroethylene fluorocarbon polymer resin.
4. A blanket assembly (10) as defined in claim 2, wherein the fluorinated polymer resin comprises fluori-nated ethylene-propylene resin.
5. A blanket assembly (10) as defined in claim 2, wherein the fluorinated polymer resin comprises a curable, fluorosilicone polymer.
6. A blanket assembly (10) as defined in claim 5, wherein the fluorosilicone polymer comprises perfluoro alkyl alkylene siloxane.
7. A blanket assembly (10) as defined in claim 5, wherein the curable fluorosilicone polymer comprise trifluoropropyl- methyl vinyl polysiloxane.
8. A blanket assembly (10) as defined in claim 1, wherein the transfer layer (28) comprises silicone elastomer resin.
9. A blanket assembly (10) as defined in claim 8, wherein the silicone elastomer resin comprises tri-chloromethylsilane copolymerized with difunctional silane.
10. A blanket assembly (10) as defined in claim 1, wherein the base carrier sheet (32) comprises polyester film.
11. A blanket assembly (10) as defined in claim 1, the transfer layer (28) comprising a spray coating of low affinity material bonded to the base carrier sheet (32).
12. A blanket assembly (10) as defined in claim 1, the transfer layer (28) comprising a film of low affinity material bonded to the base carrier sheet.
13. A blanket assembly (10) as defined in claim 1, including a resilient, compressible layer (44) disposed intermediate the base carrier sheet (32) and the liquid media transfer layer (28), the transfer layer comprising a coating of low affinity material bonded to the compressible layer (44).
14. A blanket assembly (10) as defined in claim 1, the transfer layer (28) including a compos-ite mixture (98) of a material having a low affinity for the liquid media and a material having a higher affinity for the liquid media.
15. A blanket assembly (10) as defined in claim 14, wherein the low affinity material comprises a fluori-nated polymer resin and the high affinity material compris-es nitrile rubber.
16. In a printing press (50) having a deli-very/transfer cylinder mounted on a delivery drive shaft (74) adjacent to an impression cylinder (20), coating apparatus (80) including an applicator roller (30) for transferring liquid coating material movably mounted on the press for movement to extended and retracted positions relative to the delivery/transfer cylinder, the improvement comprising a coating blanket (10) mounted on said deliv-ery/transfer cylinder for engagement with the applicator roller in the extended position, said coating blanket having a transfer layer (28) made of a non-tacky material which resists adhesion by the liquid coating material.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US7857193A | 1993-06-16 | 1993-06-16 | |
| US08/078,571 | 1993-06-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2102347A1 true CA2102347A1 (en) | 1994-12-17 |
Family
ID=22144909
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002102347A Abandoned CA2102347A1 (en) | 1993-06-16 | 1993-11-03 | Low affinity coating blanket for rotary offset presses |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0629514A1 (en) |
| JP (1) | JPH079778A (en) |
| KR (1) | KR950000389A (en) |
| CA (1) | CA2102347A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2729100B1 (en) * | 1995-01-11 | 1998-11-13 | Reeves Bros Inc | PRINTING BLANKETS FOR METAL EFFECT INK |
| DE19850968A1 (en) * | 1998-11-05 | 2000-05-25 | Roland Man Druckmasch | Wear-resistant, ink-repellent coating, especially of press components |
| JP3457932B2 (en) * | 2000-07-31 | 2003-10-20 | 三菱重工業株式会社 | Cylindrical blanket and blanket cylinder and printing press |
| WO2002032689A1 (en) * | 2000-10-18 | 2002-04-25 | Nanogate Gmbh | Method for improving the print quality of printing machines |
| DE102004054425A1 (en) | 2004-11-10 | 2006-05-18 | Weros Dienstleistungen Gmbh | Dampening solution and / or Verdruckmittelübertragungseinrichtung for printing machines |
| KR101595458B1 (en) * | 2009-08-11 | 2016-02-18 | 엘지디스플레이 주식회사 | Apparatus of fabricating thin film pattern |
| DE102010020250A1 (en) * | 2010-05-11 | 2011-11-17 | Heidelberger Druckmaschinen Ag | film clocking |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2718224A1 (en) * | 1976-05-28 | 1977-12-15 | Rubber Electronic Ind | PRINTING FELT AND PROCESS FOR ITS MANUFACTURING |
| US4479432A (en) * | 1980-05-15 | 1984-10-30 | Toppan Printing Co., Ltd. | Thick film printing method |
| JPS57205194A (en) * | 1981-06-12 | 1982-12-16 | Dainippon Screen Mfg Co Ltd | Polishing method for picture line part in thick painting |
| IT1238678B (en) * | 1990-01-26 | 1993-09-01 | Reeves Spa | FABRIC FOR COATING OF CYLINDERS OF A PRINTING PLANT, LOW AFFINITY FOR INK |
| JP2726341B2 (en) * | 1990-12-04 | 1998-03-11 | 住友ゴム工業 株式会社 | Offset blanket for printing |
| US5176077A (en) * | 1991-08-30 | 1993-01-05 | Howard W. DeMoore | Coating apparatus for sheet-fed, offset rotary printing presses |
-
1993
- 1993-11-03 CA CA002102347A patent/CA2102347A1/en not_active Abandoned
- 1993-11-04 EP EP93308812A patent/EP0629514A1/en not_active Withdrawn
- 1993-11-22 KR KR1019930024890A patent/KR950000389A/en not_active Application Discontinuation
- 1993-11-25 JP JP5321426A patent/JPH079778A/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP0629514A1 (en) | 1994-12-21 |
| KR950000389A (en) | 1995-01-03 |
| JPH079778A (en) | 1995-01-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |