Patent Publication Number: US-2018039207-A1

Title: Release layer

Description:
Electrostatic printing processes may involve creating a latent electrostatic image on a photoconductive surface, applying an imaging material having charged particles to the photoconductive surface such that the charged particles selectively bind to the latent electrostatic image while the background areas remain clean, and then transferring the charged particles in the form of the image to a print substrate. 
     The photoconductive surface may be on a cylinder and is often termed a photo-imaging plate (PIP). The photoconductive surface is selectively charged with a latent electrostatic image having image and background areas with different potentials. For example, an electrostatic ink composition comprising charged toner particles in a carrier liquid can be brought into contact with the selectively charged photoconductive surface. The charged toner particles adhere to the image areas of the latent image while the background areas remain clean. The image is then transferred to a print substrate (e.g. paper). 
     Electrostatic printing systems sometimes employ an intermediate transfer member (ITM) to transfer the charged particles, for example charged toner particles in a carrier liquid, from a photoconductive surface to a print substrate. The ITM may include a release layer which may absorb some of the liquid carrier and facilitate releasing of the charged toner particles to the print substrate. 
     Some previous methods of applying a release layer to a body of the ITM have been found to cause difficulties in controlling the surface roughness of the release layer. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a schematic illustration of an example of a coating station used in a method of coating a web with a release formulation; 
         FIG. 2  is a schematic illustration of an example of a coating station used in a method of coating a web with a release formulation; 
         FIG. 3  is a schematic illustration of an example of a coating station used in a method of coating a web with a release formulation; 
         FIG. 4  is a schematic illustration of an example of a coating station used in a method of coating a web with a release formulation; 
         FIG. 5  is a schematic illustration of a reference example of a coating station used in a reference method of coating a web with a release; 
         FIG. 6  is a cross-sectional schematic illustration of an example of a rubber blanket as described herein; 
         FIG. 7  is a cross-sectional schematic illustration of an example of an ITM as described herein; 
         FIG. 8  is a schematic illustration of a Liquid Electro Photographic (LEP) printing apparatus comprising an ITM as described herein; and 
         FIG. 9  is a graph showing “fog” behaviour of images printed using ITMs having blankets obtained using different coating methods. 
     
    
    
     DETAILED DESCRIPTION 
     Before the methods, release layers, intermediate transfer members and related aspects are disclosed and described, it is to be understood that this disclosure is not limited to the particular process features and materials disclosed herein because such process features and materials may vary somewhat. It is also to be understood that the terminology used herein is used for the purpose of describing particular examples only. The terms are not intended to be limiting because the scope of the present disclosure is intended to be limited only by the appended claims and equivalents thereof. 
     It is noted that, as used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. 
     As used herein, “copolymer” refers to a polymer that is polymerized from at least two monomers. 
     If a standard test is mentioned herein, unless otherwise stated, the version of the test to be referred to is the most recent at the time of filing this patent application. 
     As used herein, “electrostatic ink composition” generally refers to an ink composition that is typically suitable for use in an electrostatic printing process, sometimes termed an electrophotographic printing process. The electrostatic ink composition may include chargeable particles of the resin and the pigment dispersed in a liquid carrier. 
     As used herein, “electrostatic printing” or “electrophotographic printing” generally refers to the process that provides an image that is transferred from a photo imaging substrate either directly, or indirectly via an intermediate transfer member, to a print substrate. As such, the image is not substantially absorbed into the photo imaging substrate on which it is applied. Additionally, “electrophotographic printers” or “electrostatic printers” generally refer to those printers capable of performing electrophotographic printing or electrostatic printing, as described above. “Liquid electrophotographic printing” is a specific type of electrophotographic printing where a liquid ink is employed in the electrophotographic process rather than a powder toner. An electrostatic printing process may involve subjecting the electrostatic ink composition to an electric field, e.g. an electric field having a field gradient of 1000 V/cm or more, or in some examples 1500 V/cm or more. 
     As used herein, the term “about” is used to provide flexibility to a numerical range endpoint by providing that a given value may be “a little above” or “a little below” the endpoint. The degree of flexibility of this term can be dictated by the particular variable and would be within the knowledge of those skilled in the art to determine based on experience and the associated description herein. 
     All viscosities described herein are viscosities determined at 25° C. unless stated otherwise. 
     As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. 
     Sizes, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of “about 1 to about 5” should be interpreted to include not only the explicitly recited values of about 1 to about 5, but also include individual values and subranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3.5, and 4 and sub-ranges such as from 1-3, from 2-4, and from 3-5, etc. This same principle applies to ranges reciting only one numerical value. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described. 
     Unless otherwise stated, any feature described herein can be combined with any aspect or any other feature described herein. 
     In an aspect, there is provided an intermediate transfer member (ITM) comprising an outer release layer having an average surface roughness, Sa, of less than about 3 μm. 
     In an aspect, there is provided a method of coating a web with a release formulation. The method may comprise:
         providing a coating station comprising a rotatable applicator roller to apply a release formulation coating to a web;   applying a release formulation coating to a surface of the applicator roller, the release formulation comprising at least one silicone oil;   feeding the web through the coating station such that the web engages with the applicator roller; and   applying the release formulation coating to the web under a shearing force by rotating the applicator roller such that, at a location at which the web and the applicator roller engage, the surface of the applicator roller moves in the opposite direction to the direction the web is fed through the coating station.       

     In some examples, the coating station further comprises a rotatable impression roller, and the method comprises providing a nip point between the impression roller and the applicator roller at which the impression roller and the applicator roller engage with the web and the release formulation coating is applied to the web from the applicator roller. 
     In some examples, the location at which the web and the applicator roller engage is at a nip point between the applicator roller and an impression roller. 
     In some examples, the method further comprises counter-rotating an impression roller and the applicator roller, such that at a nip point between the impression roller and the applicator roller the surfaces of the applicator roller and the impression roller both move in the opposite direction to the direction in which the web is fed through the coating station. 
     In some examples, the method further comprises doctoring, for example, using a doctor blade, the release formulation coating on the surface of the applicator roller to leave a pre-determined thickness of release formulation on the surface of the applicator roller. 
     In some examples, the applicator roller comprises gravure cells on the surface of the applicator roller to accommodate a release formulation applied to the applicator roller, and applying a release formulation to the applicator roller comprises applying the release formulation to the surface of the applicator roller such that the gravure cells are filled with release formulation and doctoring the release formulation coating on the surface of the applicator roller to leave a pre-determined thickness of release formulation on the surface of the applicator roller. 
     In some examples, the coating station further comprises a gravure roller comprising gravure cells to accommodate a release formulation, the method comprising positioning the gravure roller to apply a release formulation to the applicator roller. 
     In some examples, applying a release formulation to the applicator roller comprises: applying the release formulation to the surface of a gravure roller such that gravure cells of the gravure roller are filled with a release formulation; doctoring the release formulation on the surface of the gravure roller to leave a pre-determined thickness of release formulation on the surface of the gravure roller; and transferring the pre-determined thickness of the release formulation on the surface of the gravure roller to the applicator roller. 
     In some examples, the speed of the applicator roller at the location at which the web and the applicator roller engage, for example at a nip point between the applicator roller and an impression roller (where present), is between about 50% and about 150% of the speed at which the web is fed through the coating station. In some examples, the speed of the applicator roller at the location at which the web and the applicator roller engage is between about 110% and about 120% of the speed at which the web is fed through the coating station. 
     Release Formulation 
     In some examples, the release formulation comprises at least one silicone oil having alkene groups linked to the silicone chain of the silicone oil and a cross-linker comprising a silicone hydride component. In some examples, such release formulations, on curing, may form a release layer comprising the cross-linked addition cured product of at least one silicone oil having alkene groups linked to the silicone chain of the silicone oil and a cross-linker comprising a silicone hydride component. 
     In some examples, the release formulation may contain a catalyst, for example a platinum containing catalyst or a rhodium containing catalyst. 
     In some examples, the at least one silicone oil may comprise a polysiloxane having at least two alkene groups per molecule. 
     In some examples, the silicon hydride component may comprise a polysiloxane having a silicon hydride moiety. 
     In some examples, the at least one silicone oil has the formula (I): 
     
       
         
         
             
             
         
       
     
     wherein:
 
each R is independently selected from C 1-6  alkyl and C 2-6  alkenyl groups, at least two R groups being an alkenyl group; and
 
t is an integer of at least 1, in some examples at least 10, in some examples at least 100.
 
     In some examples, the alkenyl groups are vinyl groups and the alkyl groups are methyl groups. 
     In some examples, the silicone oil has a dynamic viscosity of 100 mPa·s or more, in some examples 200 mPa·s or more, in some examples 300 mPa·s or more, in some examples 400 mPa·s or more. 
     In some examples, the silicone oil has a dynamic viscosity of 5000 mPa·s or less, in some examples 1000 mPa·s or less, in some examples 900 mPa·s or less, in some examples 800 mPa·s or less, in some examples 700 mPa·s or less, in some examples 600 mPa·s or less. 
     In some examples, the silicone oil has a dynamic viscosity of 100 to 5000 mPa·s, in some examples 100 to 1000 mPa·s, in some examples 200 to 1000 mPa·s, in some examples 200 to 900 mPa·s, in some examples 300 to 800 mPa·s, in some examples 400 to 700 mPa·s, in some examples 400 to 600 mPa·s, in some examples about 500 mPa·s. 
     In some examples, the silicone oil comprises a dimethylsiloxane homopolymer, in which the alkene groups are vinyl, and are each covalently bonded to end siloxyl units. In some examples, the silicone oil comprises a dimethylsiloxane homopolymer of the α,ω(dimethyl-vinylsiloxy)poly(dimethylsiloxyl) type. In some examples, the dimethylsiloxane homopolymer has a dynamic viscosity of at least 100 mPa·s. In some examples, the dimethylsiloxane homopolymer has a dynamic viscosity of from 100 to 1000 mPa·s, in some examples 200 to 900 mPa·s, in some examples 300 to 800 mPa·s, in some examples 400 to 700 mPa·s, in some examples 400 to 600 mPa·s, in some examples about 500 mPa·s. 
     In some example, the silicone oil comprises a co-polymer of vinylmethylsiloxane and dimethylsiloxane, and in some examples, a vinyl group is covalently bonded to each of the end siloxyl units of the co-polymer. In some examples the co-polymer of vinylmethylsiloxane and dimethylsiloxane is of the poly(dimethylsiloxyl)((methylvinylsiloxy)α,ω(dimethyl-vinylsiloxy) type. 
     In some examples, the silicone oil comprises a dimethylsiloxane homopolymer, in which the alkene groups are vinyl, and are each covalently bonded to end siloxyl units, which may be as described above and a co-polymer of vinylmethylsiloxane and dimethylsiloxane, and, in some examples a vinyl group is covalently bonded to each of the end siloxane units of the co-polymer. 
     In some examples, the co-polymer of vinylmethylsiloxane and dimethylsiloxane has a dynamic viscosity of from 1000 to 5000 mPa·s. In some examples, the co-polymer of vinylmethylsiloxane and dimethylsiloxane has a dynamic viscosity of from 2000 to 4000 mPa·s, in some examples a dynamic viscosity of from 2500 to 3500 mPa·s, in some examples a dynamic viscosity of about 3000 mPa·s. 
     The silicon hydride component may comprise a polysiloxane having a silicon hydride (Si—H) moiety. The silicon hydride moiety may be at an end siloxyl unit or an intermediate siloxyl unit in the polysiloxane of the silicon hydride component. In some examples, the silicon hydride component is selected from a polysiloxane of the poly(dimethylsiloxy)-(siloxymethylhydro)-α,ω-(dimethylhydrosiloxy) type and α,ω-(dimethylhydrosiloxy) poly-dimethylsiloxane. In some examples, the polysiloxane having a silicon hydride (Si—H) moiety has a dynamic viscosity of at least 100 mPa·s, in some examples at least 500 mPa·s. In some examples, the polysiloxane having a silicon hydride (Si—H) moiety has a dynamic viscosity of from 100 mPa·s to 2000 mPa·s, in some examples a dynamic viscosity of from 300 mPa·s to 1500 mPa·s, in some examples a dynamic viscosity of from 500 mPa·s to 1300 mPa·s, in some examples a dynamic viscosity of from 700 mPa·s to 1100 mPa·s, in some examples a dynamic viscosity of from 800 mPa·s to 1000 mPa·s, in some examples a dynamic viscosity of around 900 mPa·s. 
     In some examples, viscosities described herein may be determined according to ASTM D4283-98(2010) Standard Test Method for Viscosity of Silicone Fluids. In some examples, viscosities described herein may be measured on a viscometer, such as a Brookfield DV-II+ Programmable viscometer, using appropriate spindles, including, but not limited to, a spindle selected from spindle LV-4 (SP 64) 200-1,000 [mPa·s] for Newtonian fluids (pure silicones) and spindle LV-3 (SP 63) 200-400000 [mPa·s] for non-Newtonian fluids (silicone oils with carbon black additives or other fillers). 
     In some examples, the release formulation may comprise a silicone oil comprising a silanol terminated polysiloxane and a condensation cure cross-linker component. In some examples, the silanol terminated polysiloxane may be a silanol terminated polydimethlysiloxane. In some examples, silanol terminated polysiloxane may comprise at least two silanol groups per molecule. In some examples, a release formulation comprising a silanol terminated polysiloxane may further comprise a condensation cure cross-linking catalyst. In some examples, the condensation cure cross-linking catalyst may be a tin containing catalyst. In some examples the condensation cure cross-linker component may be an acetoxy silane component, an alkoxy silane component, an oxime component, an enoxy silane component, an amino silane component, or a benzamido silane component. In some examples, such release formulations may form, on curing, a release layer comprising the cross-linked condensation cured product of at least one silanol terminated polysiloxane. 
     In some examples, the release formulation has a viscosity of 100 to 20000 mPa·s. 
     Intermediate Transfer Member (ITM) 
     In an aspect, there is provided an intermediate transfer member (ITM) for use in an electrostatic printing process. The ITM may comprise:
         a rubber blanket comprising a release layer disposed on a web obtainable by a method described above; and   a base on which the blanket is disposed.       

     In some examples, the release layer has an average surface roughness, Sa, of less than about 3 μm. In some examples, the release layer has an average surface roughness, Sa, of less than about 2.5 μm. In some examples, the release layer has an average surface roughness, Sa, of less than about 2 μm. 
     The average surface roughness, Sa, is the arithmetic mean surface height evaluated over the complete 3D surface of the release layer. 
     The average surface roughness, Sa can be evaluated mathematically as follows: 
         S   a =∫∫ a   |Z ( x,y )| dxdy  
 
     Where Z(x,y) is a function representing the height of the surface relative to the surface relative to the best fitting plane or cylinder. The “a” used in the above integral expression is used to note that integration is performed over the area of measurement and then normalised by the cross-sectional area of the measurement. 
     The average surface roughness, Sa, may be determined using an optical microscope having the ability to scan in the z-axis. For example, Sa may be determined using LEXT 3D Measuring Laser Microscope OSL4000, by Olympus corporation to scan the 3D image of the surface of the release layer and applying a LEXT program imaging analysis algorithm (according to the mathematical definition of Sa above) to the scanned image. 
     In an aspect, there is provided an intermediate transfer member (ITM) for use in an electrostatic printing process. The ITM may comprise:
         a base; and   a rubber blanket disposed on the base, the rubber blanket comprising a release layer disposed on a web,
 
wherein the release layer comprises the cross-linked addition cured product of at least one silicone oil having alkene groups linked to the silicone chain of the silicone oil and a cross-linker comprising a silicone hydride component, the release layer having an average surface roughness, Sa, of less than 3 μm.
       

     In some examples, the release layer may have a thickness of about 3 μm or greater. 
     In some examples, the release layer may have a thickness of about 5 μm or greater. 
     In some examples, the release layer may have a thickness of about 7 μm or greater. 
     In some examples, the release layer has a thickness of about 3 μm to about 20 μm. 
     In some examples, the release layer has a thickness of about 5 μm to about 20 μm. 
     In some examples, the release layer has a thickness of about 7 μm to about 20 μm. 
     In some examples, the release layer has a thickness of about 7 μm to about 15 μm. 
     In some examples, the release layer has a thickness of about 5 μm to about 17 μm. 
     In some examples, the base of the ITM may have a cylindrical shape, as such the ITM may be suitable for use as a roller, for example a roller in a printing apparatus. In some examples, the base is a metal base. 
     The web may comprise a layered structure on which a release layer may be disposed. The layered structure may comprise a rubber layer, on which the release layer may be disposed. 
     The rubber blanket may be a section of a web on which a release layer is disposed. The rubber blanket may comprise a layered structure on which the release layer is disposed. The layered structure may be disposed on the base of the ITM. 
     The layered structure may comprise a rubber layer comprising an acrylic rubber (ACM), a nitrile rubber (NBR), a hydrogenated nitrile rubber (HNBR), a polyurethane elastomer (PU), an EPDM rubber (an ethylene propylene diene terpolymer), a fluorosilicone rubber (FMQ or FLS), a fluorocarbon rubber (FKM or FPM) or a perfluorocarbon rubber (FFKM). 
     The layered structure may comprise a primer layer to facilitate bonding or joining of the release layer to the rubber layer. In some examples, the primer layer is disposed on the rubber layer. 
     In some examples, the primer layer may comprise an organosilane. In some examples, the organosilane may be an organosilane derived from an epoxysilane such as 3-glycidoxypropyl trimethylsilane. 
     In some examples, the primer layer may comprise a catalyst. In some examples the catalyst may be a titanium containing catalyst and/or platinum containing catalyst. In some examples the catalyst may be a tin containing catalyst. 
     In some examples, the primer layer may comprise an organosilane, for example, an organosilane derived from an epoxysilane such as 3-glycidoxypropyl trimethylsilane, a vinyl silane such as vinyltriethoxysilane, a vinyltriethoxysilane, an allyl silane, or an unsaturated silane. In some examples, the primer layer may comprise a catalyst. In some examples the catalyst may be a titanium containing catalyst and/or platinum containing catalyst. 
     The primer layer may be formed from a curable primer layer. The curable primer layer may be applied to the rubber layer of the web of the rubber blanket of the ITM before the release layer is formed on the web. The curable primer layer may comprise an organosilane and a catalyst. In some examples, the catalyst may be a platinum containing catalyst. 
     In some examples the organosilane contained in the curable primer layer is selected from an epoxysilane, a vinyl silane, an allyl silane, an unsaturated silane, or combinations thereof. 
     The curable primer layer may comprise a first primer and a first catalyst, and a second primer and a second catalyst. The first primer and/or the second primer may comprise an organosilane. The organosilane may be selected from an epoxysilane, a vinyl silane, an allyl silane and an unsaturated silane. 
     In some examples, the first catalyst is a catalyst for catalysing a condensation cure reaction, for example a catalyst comprising titanium. The first primer may be cured by a condensation reaction by the first catalyst. In some examples, the second primer may be cured by a condensation reaction by the first catalyst. 
     In some examples, the second catalyst is a catalyst for catalysing an addition cure reaction. In such cases, the second catalyst may catalyse an addition cure reaction of the release formulation to form the release layer. 
     The curable primer layer may be applied to the rubber layer as a composition containing the first and second primer and first and second catalyst. 
     In some examples the curable primer layer may be applied to the rubber layer as two separate compositions, one containing the first primer and first catalyst, the other containing the second primer and second catalyst. 
     In some examples, the ITM may comprise an adhesive layer for joining the rubber layer to the base. The adhesive layer may comprise or consist of a fabric layer, for example a woven or non-woven cotton, synthetic, combined natural and synthetic, or treated, for example, treated to have improved heat resistance, material. 
     The rubber layer may be formed of a plurality of rubber layers. For example, the rubber layer may comprise a compressible layer, a compliance layer and/or a conductive layer. 
     In some examples, the compressible layer may be disposed on the base of the ITM. 
     In some examples, the compressible layer may be joined to the base of the ITM by the adhesive layer. In some examples, a conductive layer may be disposed on the compressible layer. In some examples, the compliance layer may then be disposed on the conductive layer if present, or disposed on the compressible layer if no conductive layer is present. 
     The compressible layer may be a rubber layer which, for example, may comprise an acrylic rubber (ACM), a nitrile rubber (NBR), a hydrogenated nitrile rubber (HNBR), a polyurethane elastomer (PU), an EPDM rubber (an ethylene propylene diene terpolymer), a fluorosilicone rubber (FLS or FMQ), or a fluorocarbon rubber (FKM or FPM) or a perfluorocarbon rubber (FFKM). 
     The compliance layer may comprise a soft elastomeric material having a Shore A hardness of less than about 65, or a Shore A hardness of less than about 55 and greater than about 35, or a Shore A hardness value of between about 42 and about 45. In some examples, the compliance layer  27  comprises a polyurethane or acrylic. Shore A hardness may be determined by ASTM standard D2240. 
     In some examples, the compliance layer comprises an acrylic rubber (ACM), a nitrile rubber (NBR), a hydrogenated nitrile rubber (HNBR), a polyurethane elastomer (PU), an EPDM rubber (an ethylene propylene diene terpolymer), a fluorosilicone rubber (FLS or FMQ), a fluorocarbon rubber (FKM or FPM) or a perfluorocarbon rubber (FFKM) 
     The conductive layer may comprise a rubber, for example an acrylic rubber (ACM), a nitrile rubber (NBR), a hydrogenated nitrile rubber (HNBR), a polyurethane elastomer (PU), an EPDM rubber (an ethylene propylene diene terpolymer), a fluorosilicone rubber (FLS or FMQ), a fluorocarbon rubber (FKM or FPM) or a perfluorocarbon rubber (FFKM) and a conductive material. 
     In some examples, the compressible layer and/or the compliance layer may be made to be partially conducting with the addition of a conductive material, for example conducting particles such as conductive carbon black or metal fibres. In some examples, where the compressible layer and/or the compliance layer are partially conducting there may be no requirement for an additional conductive layer. 
     Method of Coating a Web with a Release Formulation 
       FIG. 1  shows an example of a coating station  1  which may be used in a method of coating a web  4  with a release formulation. The coating station  1  comprises a rotatable applicator roller  2  having a surface  3  to which a release formulation coating may be applied. The web  4  may be fed through the coating station  1  such that the web  4  engages with the applicator roller  2  at a location indicated by reference numeral  6  in  FIG. 1 . A release formulation coating may be applied to the web  4  under a shearing force by feeding the web  4  through the coating station  1  in the direction indicated by arrow A and rotating the applicator roller in the direction indicated by arrow B such that at a location  6  at which the web  4  and the applicator roller  2  engage, the surface  3  of the applicator roller  2  moves in the opposite direction to the direction the web  4  is fed through the coating station  1 . 
       FIG. 2  shows an example of a coating station  200  used in a method coating a web  4  with a release formulation. Reference numerals used in  FIG. 2  which correspond to reference numerals of  FIG. 1  illustrate features corresponding to those described above in relation to  FIG. 1 . The coating station  200  further comprises a rotatable impression roller  8  which is positioned such as to provide a nip point  6  between the impression roller  8  and the applicator roller  2  at which the impression roller  8  and the applicator roller  2  may engage with the web  4 . As the web  4  is fed through the coating station  200  in the direction shown by arrow A, a release formulation coating may be applied to the web  4  from the applicator roller  2 . The impression roller  8  may be provided in order to apply pressure to the web  4  as it is moved through the nip point  6  between the applicator roller  2  and the impression roller  8 , for example to ensure that a release formulation coating is transferred from the surface  3  of applicator roller  2  to the web  4 . In this illustrative example, the impression roller  8  may be rotated in the direction shown by arrow C so that the applicator roller  2  and the impression roller  8  are counter-rotated such that at the nip point the surfaces of the applicator roller and the impression roller both move in the opposite direction to the direction in which the web is fed through the nip point  6  of the coating system. 
       FIG. 3  shows an example of a coating station  300  used in a method coating a web  4  with a release formulation. Reference numerals used in  FIG. 3  which correspond to reference numerals of  FIGS. 1 and 2  illustrate features corresponding to those described above in relation to  FIGS. 1 and 2 . The coating station  300  further comprises a doctor blade  12  which may be used to doctor a release formulation coating applied to the surface  3  of the applicator roller  2  to leave a pre-determined thickness of release formulation coating on the surface of the applicator roller such that a pre-determined thickness of a release formulation coating may be applied to the web  4 . 
     As illustrated in the example shown in  FIG. 3 , the applicator roller  2  may comprises gravure cells  14  on the surface of the applicator roller  2  for accommodating a release formulation applied to the applicator roller. In a method of coating a web  4  with a release formulation, applying a release formulation to the applicator roller may comprise applying the release formulation to the surface of the applicator roller such that the gravure cells  14  are filled with release formulation. The method may also involve doctoring the release formulation coating on the surface  3  of the applicator roller  2  using a doctor blade  12  to leave a pre-determined thickness of release formulation coating on the surface of the applicator roller  2 . The pre-determined thickness of release formulation coating may then be transferred to the web  4  as the web  4  is fed through the nip point  6  between the applicator roller  2  and the impression roller  8  in the direction indicated by arrow A. The release formulation coating is applied under a shearing force as the surface  3  of the applicator roller  2 , from which the release formulation coating is applied to the web  4 , moves in the opposite direction (indicated by arrow B) to the direction in which the web  4  is fed through the nip point  6  (indicated by arrow A). This method described in relation to the coating station  300  shown in  FIG. 3  in which a release formulation is applied to an applicator roller  2  having gravure cells  14 , and then the release formulation on the surface of the applicator roller  2  is doctored to leave a release formulation coating having a pre-determined thickness on the surface of the applicator roller  2  before the release formulation coating is transferred to a web  4  under a shearing force at a nip point  6  between the applicator roller  2  and an impression roller  8  as the surface  3  of the applicator roller  2  moves in the opposite direction to the direction in which the web  4  is moved through the nip point  6  is described herein as the “reverse gravure coating method”. 
       FIG. 4  shows an example of a coating station  400  used in a method coating a web  4  with a release formulation. Reference numerals used in  FIG. 4  which correspond to reference numerals of  FIGS. 1, 2 and 3  illustrate features corresponding to those described above in relation to  FIGS. 1, 2 and 3 . Coating station  400  comprises a gravure roller  16  comprising gravure cells  14  to accommodate a release formulation. In a method of coating a web  4 , the method may include applying the release formulation to the surface  17  of the gravure roller  16  such that the gravure cells  14  are filled with release formulation. The method may also include doctoring the release formulation on the surface  17  of the gravure roller  16 , for example using a doctor blade  12 , to leave a pre-determined thickness of release formulation on the surface of the gravure roller. The method may further include transferring the pre-determined thickness of the release formulation coating from the surface  17  of the gravure roller  16  to the applicator roller  2  as the gravure roller  16  and the applicator roller  2  are counter-rotated as shown by the arrows B and D. The release formulation coating can then be transferred from the of the applicator roller  2  to the web  4  under a shearing force at a nip point  6  between the applicator roller  2  and an impression roller  8  as the surface  3  of the applicator roller  2  moves in the opposite direction to the direction in which the web  4  is moved through the nip point  6 . This method described above in relation to  FIG. 4  in which the coating station comprises a gravure roller  17  to which a release formulation is applied and then doctored to form a release formulation coating having a pre-determined thickness before being transferred to an applicator roller  2 , the applicator roller  2  being positioned between the gravure roller  16  and the impression roller, is described herein as the “off-set reverse gravure coating method”. 
       FIG. 5  shows a reference example of a coating station  50  which can be used in reference methods of coating a web  54  with a release formulation in which a web  54  is fed through a coating station  50  comprising an applicator roller  52  and an impression roller  58 . At a nip point  56  between the applicator roller  52  and the impression roller  58  a release formulation may be applied to the web  54  from the applicator roller  52 . At the nip point  56  the web  54  moves in the same direction (indicated by arrow A) as the direction in which the surface  53  of the applicator roller  52  is moving. This reference method is described herein as the “direct gravure coating method”. 
     Rubber Blanket 
       FIG. 6  is a cross-sectional schematic illustration of an example of a rubber blanket  60  comprising a web  4  as described herein on which a release layer  30  has been formed. The release layer  30  may be formed on the web  4  by first coating the web  4  with a release formulation as described above. The release formulation coating on the web  4  may then be cured to form a release layer  30  disposed on the web  4 , the web  4  with the release layer  30  may then be cut into sections of rubber blanket  60 . A rubber blanket  60  may then be wrapped around supportive portion, such as a base cylinder, to form an intermediate transfer member (ITM). 
     The rubber blanket  60  illustrated in  FIG. 6  comprises a web  4  on which a release layer  30  is disposed. The web  4  may comprise a rubber layer  20  on which a primer layer  28  is disposed. The release layer  30  of the rubber blanket  60  may be disposed on the primer layer  28  of the web  4 . 
     The rubber layer  20  may comprise an acrylic rubber (ACM), a nitrile rubber (NBR), a hydrogenated nitrile rubber (HNBR), a polyurethane elastomer (PU), an EPDM rubber (an ethylene propylene diene terpolymer), a fluorosilicone rubber (FMQ or FLS), a fluorocarbon rubber (FKM or FPM) or a perfluorocarbon rubber (FFKM). For example, the rubber layer may comprise an at least partly cured acrylic rubber, for example an acrylic rubber comprising a blend of acrylic resin Hi-Temp 4051 EP (Zeon Europe GmbH, Niederkasseler Lohweg 177, 40547 Dusseldorf, Germany) filled with carbon black pearls  130  (Cabot, Two Seaport Lane, Suite 1300, Boston, Mass. 02210, USA) and a curing system which may comprise, for example, NPC-50 accelerator (ammonium derivative from Zeon). 
     The rubber layer  20  may comprise a compressible layer  22 , a conductive layer  24  disposed on the compressible layer  22 , and a compliance layer  26  disposed on the conductive layer  24 . 
     The web  4  may also comprise an adhesive layer  21  on which the rubber layer  20  is disposed. The adhesive layer  21  may be a fabric layer, for example a woven or non-woven cotton, synthetic, combined natural and synthetic, or treated, for example, treated to have improved heat resistance, material. In an example the adhesive layer  21  is a fabric layer formed of NOMEX material having a thickness, for example, of about 200 μm. 
     The compressible layer  22  may be a rubber layer which, for example, may comprise an acrylic rubber (ACM), a nitrile rubber (NBR), a hydrogenated nitrile rubber (HNBR), a polyurethane elastomer (PU), an EPDM rubber (an ethylene propylene diene terpolymer), or a fluorosilicone rubber (FLS). 
     The compliance layer  26  may comprise a soft elastomeric material having a Shore A hardness of less than about 65, or a Shore A hardness of less than about 55 and greater than about 35, or a Shore A hardness value of between about 42 and about 45. In some examples, the compliance layer  26  comprises a polyurethane or acrylic. Shore A hardness may be determined by ASTM standard D2240. 
     In some examples, the compliance layer comprises an acrylic rubber (ACM), a nitrile rubber (NBR), a hydrogenated nitrile rubber (HNBR), a polyurethane elastomer (PU), an EPDM rubber (an ethylene propylene diene terpolymer), a fluorosilicone rubber (FMQ), a fluorocarbon rubber (FKM or FPM) or a perfluorocarbon rubber (FFKM) 
     In some examples, the compressible layer  22  and the compliance layer  26  are formed from the same material. 
     In some examples, the conductive layer  24  comprises a rubber. In some examples, the rubber may be an acrylic rubber (ACM), a nitrile rubber (NBR), a hydrogenated nitrile rubber (HNBR), a polyurethane elastomer (PU), an EPDM rubber (an ethylene propylene diene terpolymer, a fluorosilicone rubber (FMQ), a fluorocarbon rubber (FKM or FPM) or a perfluorocarbon rubber (FFKM) and a conductive material. In some examples, the conductive layer  24  may be omitted. For example, the conductive layer  24  may be omitted in examples in which the compressible layer  22 , the compliance layer  26 , or the release layer  30  are partially conducting. For example, the compressible layer  222  and/or the compliance layer  26  may be made to be partially conducting with the addition of conductive carbon black or metal fibres. 
     The primer layer  28  may be provided to facilitate bonding or joining of the release layer  30  to the rubber layer  20 . The primer layer  28  may comprise an organosilane, for example, an organosilane derived from an epoxysilane such as 3-glycidoxypropyl trimethylsilane, a vinyl silane such as vinyltriethoxysilane, an allyl silane, or an unsaturated silane, and a catalyst such as a titanium containing catalyst and/or a platinum containing catalyst. 
     In an example, a curable primer layer is applied to the rubber layer  20 . In some examples, a curable primer layer is applied to the compliance layer  26  of a rubber layer  20 , for example to the outer surface of a compliance layer  26  made from an acrylic rubber. In some examples, the curable primer layer may be applied using a rod coating process. In some examples, the curable primer layer may be applied using a direct gravure coating method as described herein. 
     In some examples, the curable primer may comprise an organosilane and a catalyst comprising tin. 
     In some examples, the curable primer may comprise a first primer comprising an organosilane and a first catalyst comprising titanium, for example an organic titanate or a titanium chelate. In an example the organosilane is an epoxysilane, for example 3-glycidoxypropyl trimethoxysilane (available from ABCR GmbH &amp; Co. KG, Im Schlehert 10 D-76187, Karlsruhe, Germany, product code SIG5840) and vinyltriethoxysilane (VTEO, available from Evonik, Kirschenallee, Darmstadt, 64293, Germany), vinyltriethoxysilane, an allyl silane or an unsaturated silane. The first primer is curable by, for example, a condensation reaction. For example, the first catalyst for a silane condensation reaction may be an organic titanate such as Tyzor® AA75 (available from Dorf-Ketal Chemicals India Private Limited Dorf Ketal Tower, D&#39;Monte Street, Orlem, Malad (W), Mumbai-400064, Maharashtra INDIA.). The primer may also comprise a second primer comprising an organosilane, e.g. a vinyl siloxane, such as a vinyl silane, for example vinyltriethoxysilane or vinyltrimethoxysilane, an allyl silane or an unsaturated silane, and, in some examples, a second catalyst. The second primer may also be curable by a condensation reaction. In some examples, the second catalyst, if present, may be different from the first catalyst and in some examples comprises platinum or rhodium. For example, the second catalyst may be a Karstedt catalyst with, for example, 9% platinum in solution (available from Johnson Matthey, 5th Floor, 25 Farringdon Street, London EC4A 4AB, United Kingdom) or a SIP6831.2 catalyst (available from Gelest, 11 East Steel Road, Morrisville, Pa. 19067, USA). 
     In some examples, the second catalyst is a catalyst for catalysing an addition cure reaction. In such cases the second catalyst may catalyse an addition cure reaction of the release formulation coating applied to the web  4  to form the release layer  30  when the release formulation comprises at least one silicone oil having alkene groups linked to the silicone chain of the silicone oil, for example a vinyl functional siloxane and a cross-linker comprising a silicone hydride component. 
     The curable primer layer applied to the rubber layer  20  may comprise a first primer and/or a second primer. The curable primer layer may be applied to the rubber layer  20  as two separate layers, one layer containing the first primer and the other layer containing the second primer. 
     The rubbers of the compressible layer  22 , the conductive layer  24  and/or the compliance layer  26  of the rubber layer  20  may be uncured when the curable primer layer is applied thereon. 
     In some examples, the release layer  30  of the rubber blanket  60  may comprise the cross-linked addition cured product of at least one silicone oil having alkene groups linked to the silicone chain of the silicone oil and a cross-linker comprising a silicone hydride component. 
     In some examples, the release layer  30  may be formed on the web  4  by applying a release formulation coating to a web  4  as described herein. For example, the release formulation coating may be applied to the rubber layer  20  of a web  4  or on top of a curable primer layer which has already been applied to the rubber layer  20  of the web  4 . 
     The release formulation may comprise at least one silicone oil. 
     In some examples, the release formulation may comprise at least one silicone oil having alkene groups linked to the silicone chain of the silicone oil and a cross-linker comprising a silicon hydride component. In some examples, the release formulation may contain a catalyst, for example a platinum containing catalyst or a rhodium containing catalyst. 
     In some examples, the at least one silicone oil may comprise a polysiloxane having at least two alkene groups per molecule. For example, the silicone oil may comprise a dimethylsiloxane homopolymer, in which the alkene groups are vinyl, and are each covalently bonded to end siloxyl units. In some examples, the silicone oil comprises a dimethylsiloxane homopolymer of the α,ω(dimethyl-vinylsiloxy)poly(dimethylsiloxyl) type. 
     In some example, the at least one silicone oil comprises a co-polymer of vinylmethylsiloxane and dimethylsiloxane, and in some examples, a vinyl group is covalently bonded to each of the end siloxyl units of the co-polymer. In some examples the co-polymer of vinylmethylsiloxane and dimethylsiloxane is of the poly(dimethylsiloxyl)((methylvinylsiloxy)α,ω(dimethyl-vinylsiloxy) type. 
     In some examples, the silicone oil comprises a dimethylsiloxane homopolymer, in which the alkene groups are vinyl, and are each covalently bonded to end siloxyl units, which may be as described above and a co-polymer of vinylmethylsiloxane and dimethylsiloxane, and, in some examples a vinyl group is covalently bonded to each of the end siloxane units of the co-polymer. 
     The silicon hydride component may comprise a polysiloxane having a silicon hydride (Si—H) moiety. The silicon hydride moiety may be at an end siloxyl unit or an intermediate siloxyl unit in the polysiloxane of the silicon hydride component. In some examples, the silicon hydride component is selected from a polysiloxane of the poly(dimethylsiloxy)-((siloxymethylhydro)-α,ω-(dimethylhydrosiloxy) type and α,ω-(dimethylhydrosiloxy) poly-dimethylsiloxane. 
     In some examples, the silicone oil comprises a polydimethlysiloxane. 
     In some examples, the release formulation may comprise a silicone oil comprising a silanol terminated polysiloxane. In some examples, the silanol terminated polysiloxane may be a silanol terminated polydimethlysiloxane. In some examples, a release formulation comprising a silanol terminated polysiloxane may further comprise a tin catalyst. In some examples, such release formulations may form a release layer comprising the cross-linked condensation cured product of at least one silanol terminated polysiloxane. 
     Once cured, the rubber blanket  60  comprises a release layer  30  disposed on a rubber layer  20 , or, if present, disposed on a primer layer  28  of a web  4 . 
     Intermediate Transfer Member (ITM) 
       FIG. 7  is a cross-sectional schematic illustration of an ITM  70 . The ITM comprises a base  19  and a web  4  (as described above) disposed on the base  19 . The base  19  may be a metal cylinder. The ITM  70  also comprises a release layer  30  disposed on the web  4 . The web  4  along with the release layer  30  make up the rubber blanket  60  as described above. 
     The ITM  70  may be formed by applying a rubber blanket  60  (as described above) to a base  19 , for example wrapping a rubber blanket  60  around a metal cylinder. 
     Electrostatic Liquid Electro Photographic (LEP) Printing Apparatus 
       FIG. 8  shows a schematic illustration of an LEP printing apparatus  800  comprising an example of an ITM  70  as described herein. An image, including any combination of graphics, text and images, is communicated to the LEP printing apparatus  800 . The LEP includes a photo charging unit  802  and a photo-imaging cylinder  804 . The image is initially formed on a photo-conductive member in the form of a photo-imaging cylinder  804  before being transferred (first transfer) to a release layer  30  of the ITM  70  which is in the form of a roller, and then from the release layer  30  of the ITM  70  to a print substrate  806  (second transfer). 
     According to an illustrative example, the initial image is formed on a rotating photo-imaging cylinder  804  by the photo charging unit  802 . Firstly, the photo charging unit  802  deposits a uniform static charge on the photo-imaging cylinder  804  and then a laser imaging portion  803  of the photo charging unit  802  dissipates the static charges in selected portions of the image area on the photo-imaging cylinder  804  to leave a latent electrostatic image on the surface of the photo-imaging cylinder  804 . The latent electrostatic image is an electrostatic charge pattern representing the image to be printed. Ink (for example, a liquid electrostatic ink such as ElectroInk® or any other Liquid Electro Photographic (LEP) inks developed by Hewlett-Packard Company) may then transferred to the photo-imaging cylinder  804  by Binary Ink Developer (BID) units  808 . The BID units  808  present a uniform film of ink to the photo-imaging cylinder  804 . The ink contains electrically charged pigment particles which are attracted to the latent electrostatic image on the photo-imaging cylinder  804 . The ink is repelled from the uncharged, non-image areas and forms a developed toner image on the surface of the latent electrostatic image. 
     The developed toner image is then transferred from the photo-imaging cylinder  804  to the outer release layer  30  of the ITM  70  by virtue of an appropriate potential applied between the photo-imaging cylinder  804  and the ITM  70 , such that the charged ink is attracted to the ITM  70 . The image is then dried and fused on the release layer  30  of the ITM  70  before being transferred from the release layer  30  of the ITM  70  to a print substrate  806 . 
     Between the first and second transfers the solid content of the developed toner image may be increased and the ink may be fused on to the ITM  70 . For example, the solid content of the developed toner image deposited on the outer release layer  30  after the first transfer may be around 20%, by the second transfer the solid content of the developed toner image may be around 80-90%. This drying and fusing may be achieved by using elevated temperatures and/or air flow assisted drying. In some examples, the ITM  70  is heatable. 
     In some examples, a substrate primer may be applied to a print substrate before a toner image is transferred to a print substrate. 
     Examples 
     It is to be understood that the following examples are illustrative of the application of the principles of the present methods, intermediate transfer members, release layers and related aspects. Numerous modifications and alternative methods, intermediate transfer members, release layers and related aspects may be devised by those skilled in the art without departing from the spirit and scope of the present methods, intermediate transfer members, release layers and related aspects. The appended claims are intended to cover such modifications and arrangements. Thus, while the present methods, intermediate transfer members, release layers and related aspects have been described above with particularity, the following examples provide further detail in connection with what are presently deemed to be acceptable. 
     Rubber Blanket Structure and Release Formulation Coating 
     The rubber blanket structure from bottom to top (top is a release layer; bottom is a layer which is placed in contact with the base, i.e. metal drum of the ITM) produced and tested in the following examples was as follows:
         1. Fabric based (in these examples, cotton for Gemini blanket, cotton/rayon for Iris blanket) adhesive layer having a thickness of less than 250 μm;   2. Rubber based compressible layer with large range of compressibility (in these examples, NBR containing carbon black (CB) (from ContiTech AG Vahrenwalder Str. 9 30165 Hannover Germany for Gemini blanket, from Trelleborg for the Iris blanket) having a thickness of 600-700 μm;   3. Rubber based conductive layer (in these example, NBR containing CB from ContiTech for Gemini blanket and ACM containing CB from Trelleborg for Iris blanket) having a thickness of 140-300 μm;   4. Rubber based soft compliant layer (in these examples, ACM containing CB (from ContiTech for Gemini blanket, from Trelleborg for the Iris blanket) having a thickness of 80-160 μm;   5. Primer layer coated on rubber based soft compliant layer (layer no 4) using a direct gravure coating method (as described above in relation to  FIG. 5 ), the primer layer used depends on the release formulation to be applied to the primer layer, for the addition curable release formulations RL-26 or RL-61 the primer layer comprises a first layer containing a Primer 1 formulation and a second layer containing Primer 2 formulation, the Primer 1 and 2 formulations described in tables 1 and 2 below, for the condensation release layer the primer layer comprises Primer 3 formulation described in table 3 below; and   6. Release layer comprising the cured product of the release formulation described in table 4, table 5 or table 6 below, the release layers of these examples had a thickness of 5-17 μm as described below.       

     Each rubber blanket was prepared by providing a web comprising layer numbers 1 to 5 above and applying a release formulation as set out in table 3 (RL-26), table 4 (RL-61), or table 5 (condensation) to the primer layer using either a direct gravure coating method, a reverse gravure coating method or an off-set reverse gravure coating method (as described above in relation to  FIGS. 1 to 5 ). To apply a release layer to the web using the direct gravure coating method the gravure roller was rotated with the same relative speed to the speed at which the web was fed through the coating station, in these examples a speed of 5 m/min was used. To apply a release layer to the web using the reverse gravure coating method the gravure roller was rotated with a relative speed of 150% greater than the speed at which the web was fed through the coating station, in these examples the speed of the gravure roller at the nip point was 7.5 m/min and the web was fed through the coating station at a speed of 5 m/min. To apply a release layer to the web using the off-set reverse gravure coating method the gravure roller was rotated with the same relative speed to the speed at which the web was fed through the coating station, in these examples a speed of 5 m/min was used. After the coating process was complete the whole rubber blanket was placed in an oven at 120° C. for 1.5 hr. 
     The gravure roller used in each coating method was selected based on the desired thickness of the release layer to be formed. For a release layer applied using a direct gravure coating method with a desired thickness of less than 7 μm a gravure roller having a surface geometry having 220 lines/inch and 60° (hexagonal) gravure cells and a gravure volume of 13.8 cm 3 /m 2  (available from Anilox) was used. For a release layer applied using a reverse gravure coating method with a desired thickness of less than 7 μm a gravure roller having a surface geometry having 120 lines/inch and 60° (hexagonal) gravure cells and a gravure volume of 32.7 cm 3 /m 2  (available from Anilox) was used. For a release layer applied using a direct gravure coating method with a desired thickness of greater than 7 μm a gravure roller having a surface geometry having 220 lines/inch and 60° (hexagonal) gravure cells and a gravure volume of 40.0 cm 3 /m 2  (available from Anilox) was used. For a release layer applied using an off-set reverse gravure coating method with a desired thickness of greater than 7 μm a gravure roller having a surface geometry having 220 lines/inch and 60° (hexagonal) gravure cells and a gravure volume of 32.7 cm 3 /m 2  (available from Anilox) was used. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Wt. % in 
                   
               
               
                 Primer 1 Formulation 
                 formulation 
                 Supplier 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 3(Glycidoxypropyl) trimethoxysilane 
                 45 
                 ABCR 
               
               
                 3-methacryloxypropyltrimethoxysilane 
                 50 
                 ABCR 
               
               
                 2-hydroxy-2-methylpropiophenone 
                 5 
                 Ciba 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                   
                 Wt. % in 
                   
               
               
                 Primer 2 formulation 
                 formulation 
                 Supplier 
               
               
                   
               
             
            
               
                 3(Glycidoxypropyl) trimethoxysilane 
                 58-62 
                 ABCR 
               
               
                 Vinyltrimethoxysilane 
                 26 
                 ABCR 
               
               
                 Tyzor AA75 
                  8 
                 DorfKetal 
               
               
                 Karstedt solution 9% Pt 
                 4-8 
                 Johnson Mattey 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                   
                 Wt. % in 
                   
               
               
                 Primer 3 formulation 
                 formulation 
                 Supplier 
               
               
                   
               
             
            
               
                 3(Glycidoxypropyl) trimethoxysilane 
                 50 
                 ABCR 
               
               
                 Stannous octoate 
                 2-5 
                 Sigma-Aldrich 
               
               
                 o, m- or p-xylene 
                 45-48 
                 Sigma- Aldrich 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                 Parts by weight in 
                   
               
               
                 Materials - RL-26 
                 formulation 
                 Supplier 
               
               
                   
               
             
            
               
                 Dimethylsiloxane vinyl terminated - 
                 80 
                 ABCR 
               
               
                 VS 500 
               
               
                 Vinylmethylsiloxane - 
                 20 
                 ABCR 
               
               
                 Dimethylsiloxane Copolymer vinyl 
               
               
                 terminated - XPRV 5000 
               
               
                 Carbon black 
                 0-1 
                 Ketjenblack 
               
               
                   
                   
                 600JD from 
               
               
                   
                   
                 AkzoNobel) 
               
               
                 Hydride siloxane 
                 10 
                 ABCR 
               
               
                 Karstedt solution 0.5% Pt 
                 Up to 0.5 
                 ABCR 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                 Parts by weight in 
                   
               
               
                 Materials - RL-61 
                 formulation 
                 Supplier 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Dimethylsiloxane vinyl terminated - 
                 80 
                 ABCR 
               
               
                 VS 1000 
               
               
                 Vinylmethylsiloxane - 
                 20 
                 ABCR 
               
               
                 Dimethylsiloxane Copolymer vinyl 
               
               
                 terminated - XPRV 5000 
               
               
                 Carbon black 
                 0-1 
                 Ketjenblack 
               
               
                   
                   
                 600JD from 
               
               
                   
                   
                 AkzoNobel) 
               
               
                 Hydride siloxane 
                 8.6 
                 ABCR 
               
               
                 Karstedt solution 0.5% Pt 
                 Up to 0.5 
                 ABCR 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 6 
               
               
                   
               
               
                 Materials -Release 
                 Parts by weight in 
                   
               
               
                 condensation 
                 formulation 
                 Supplier 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Poly(dimethylsiloxane), silanol 
                 100 
                 Gelest 
               
               
                 terminated - DMS-S27 
               
               
                 Carbon black 
                 0.8 
                 Ketjenblack 
               
               
                   
                   
                 600JD from 
               
               
                   
                   
                 AkzoNobel) 
               
               
                 Oleic acid 
                 6 
                 Backer 
               
               
                 Ethyl silicate 
                 5 
                 Colcoat CO., 
               
               
                   
                   
                 LTD 
               
               
                 Methylsilicate 51 
                 1.5 
                 Colcoat CO., 
               
               
                   
                   
                 LTD 
               
               
                 Dibutyltin dilaurate 
                 1.2 
                 Sigma-Aldrich 
               
               
                   
               
            
           
         
       
     
     Each of the rubber blankets obtained were then applied to a metal cylinder to form an ITM. Various properties of the release layers of the rubber blankets were then tested on the ITMs in LEP printing apparatuses similar to the illustrative example of an LEP printing apparatus described in relation to  FIG. 8 . The tests were carried out as follows. The results are shown in Table 7 below. 
     Surface Roughness 
     The average surface area surface roughness, Sa, was evaluated over the complete 3D surface (Arithmetic mean height (Sa)) for each release layer using an optical microscope having the ability to scan in the z-axis, in these examples a LEXT 3D Measuring Laser Microscope OSL4000, by Olympus corporation was used to determine Sa. To determine Sa for the surface of each release layer, prior to the microscope imaging, a sample of blanket was adhered to a glass plate with two-sided adhesive tape (adhered to the fabric (adhesive layer) side). The surface of the release layer cleaned 3 times by an adhesive sticker to remove any dirtiness from the surface. This cleaning does not affect the release layer surface roughness. The 3D image of the release surface was scanned by the LEXT microscope, at magnification of ×5, and the LEXT program imaging analysis algorithm (according to the mathematical definition of Sa described above) was applied on the scanned image. The results are shown in Table 7 below. 
     The results shown in Table 7 show that the reverse gravure coating method and the off-set reverse gravure coating method can be used to produce a release layer having a lower surface roughness than a release layer produced using a reference direct gravure coating method. 
     “Fog” of Image Printed on a Print Substrate 
     “Fog” is a print quality phenomena, it is a measurement of black solid non-uniformity. Solid black images were printed on to print substrates and the deviation of grey levels analysed in the printed area. “Fog” has been found to be reduced by using an ITM having a release layer with a lower surface roughness as can be seen from the graph shown in the graph shown in  FIG. 9 . The ITMs used in an LEP printing apparatus (as described above in relation to  FIG. 8 ) to print the grey images were ITMs numbers 3 and 4 described in the table below. “Fog” is considered to be indicative of surface roughness caused by ink particles fusing into a thin film on the ITM, between the first and second transfers, following the release layer surface. For each of ITMs 3 and 4 an optimized “working point” was used, which is how much the photo-imaging cylinder  804  and the ITM  70  are pressed together during the transfer of ink from the photo-imaging cylinder  804  to the ITM  70 . As the blanket  60  of the ITM  70  is formed from rubber and photo-imaging cylinder  804  is hard, the photo-imaging cylinder  804  decreases the blanket  60  thickness during the transfer of ink from the photo-imaging cylinder  804  to the ITM  70  when the photo-imaging cylinder  804  presses against the ITM  70 . “Fog” was measured around the “working point”. For example, a negative value, is a distance below the “working point”, less pressure applied on the blanket  60  of the ITM  70  than the optimal working point. If the value from “working point is positive, more pressure is applied by the photo-imaging cylinder  804  to the blanket  60  of the ITM  70 . 
     Appearance of “Butterflies” in an Image Printed on a Print Substrate 
     The appearance of “butterflies” is a print quality phenomena, which can be seen as a “wavy pattern” on grey (20-80% coverage) prints. Grey images having 20-80% coverage were printed on to print substrates using a LEP printing apparatus (as described above in relation to  FIG. 8 ) comprising ITMs described above. The presence or absence of “butterflies” was determined. 
     As illustrated in the results that follow, “butterflies” have been found to occur on some prints when the first transfer voltage (the potential applied between the photo-imaging cylinder and the ITM) is high (above 700V). The source of the phenomena is attributed to the surface roughness of the release layer of the rubber blanket, which is believed to be created during the coating process. The results that the appearance of “butterflies” at the higher first transfer voltages can be prevented by providing a release layer with a lower surface roughness, for example an average surface roughness, Sa, of below 3 microns. 
     Interaction Between Release Layer of ITM and Substrate Primer 
     Many print substrates used in the printing industry may be pre-treated, such as by application of adhesive layer (substrate primer) on top of the print substrate. The substrate primer layer allows strong adhesion between the ink and the substrate. 
     The substrate primer can be applied before the print substrate enters the printing apparatus (off-line), or in the printing apparatus, by a priming station located before the print engine (in-line). In both cases, during the second transfer, a direct contact between the ITM (release layer) and the substrate primer occurs, at the non-printed (background) areas. This contact may lead to some transfer of the adhesive substrate primer from the print substrate to the release layer, and accumulation of the substrate primer at the non-printed areas. 
     The present inventors have found that accumulated substrate primer on the release layer may cause a decrease in print quality (memories, ink accumulation on blanket, second transfer failures), mechanical damage to the blanket and reduced utilization of the printing apparatus (due to frequent rubber blanket replacement). The inventors have found that lowering the surface area of the release layer, by reducing the surface roughness of the release layer using the reverse gravure and off-set reverse gravure coating methods described herein, reduces the accumulation of the substrate primer on the rubber blanket, and thus rubber blanket failures related to this phenomena. 
     The blankets were aged for 400 printed images and then a substrate primer solution (adhesive primer 050 (Michelman, ethylene acryl imine) was dropped onto the blanket surface using a pipette before an additional image was printed. The substrate primer solution was splashed with a pipette on the printed substrate, at a distance of 1-5 cm before the second transfer nip to produce a local excess of un-dried primer on the substrate. This excess of un-dried primer may accumulate at the background areas, where direct contact between the primed substrate and release layer occurs. At those areas a primer may accumulate and cause a rupture/tear/detachment of release layer from the blanket (called “release tear” failure). The size of “release tear” areas can vary:
         a. diameter—from few microns to centimeter scale (0.01-10 cm)   b. thickness—from 1 micron to the full thickness of the release layer (1-20 microns).       

     The “release tear” failure is the most severe failure that may be caused by accumulated primer. It can appear on print as voids and identified as dirtiness, when the diameter is large (0.5 cm and higher), or it can appear as a memory (diameter &lt;0.5 um), due to change in image roughness. 
     During the test the prints were evaluated to the presence of the “release tear” failure, as a parameter to blanket damage. 
     The results, presented in Table 7, show that the lower the surface roughness, lower the rate of the “release tear” failure. 
     The present inventors have also found that the off-set reverse gravure coating method described herein can be used to produce release layers having a thickness of about 7 μm or greater, for example, a thickness of 7-20 μm, without increase of the average surface roughness, Sa. For example, release layers having a thickness of greater than about 7 μm can be formed having an average surface roughness, Sa, of less than about 3 μm. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 7 
               
             
            
               
                   
                   
               
               
                   
                   
                 Number of failed 
               
               
                   
                 “Butterflies” 
                 blankets (out of 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                 Gravure 
                   
                 Final Release 
                 Surface 
                 First 
                 “Butterflies” 
                 3 tested) due to 
               
               
                   
                   
                 Release 
                 volume 
                 Coating 
                 layer thickness 
                 roughness 
                 transfer 
                 appear on 
                 application of 
               
               
                 ITM No. 
                 ITM type 
                 formulation 
                 (cm 3 /m 2 ) 
                 method 
                 (microns) 
                 (microns) 
                 voltage (V) 
                 gray print 
                 substrate primer 
               
               
                   
               
               
                 1 
                 Iris 
                 Addition cure 
                 32.7 
                 Off-set reverse 
                 About 10 
                 1.7 
                   
                   
                 1 
               
               
                   
                   
                 RL-61 
                   
                 gravure 
               
               
                 2 
                 Iris 
                 Addition cure 
                 32.7 
                 Reverse 
                 5.5-6.5 
                 1.4 ± 0.2 
                   
                   
                 1 
               
               
                   
                   
                 RL-61 
                   
                 gravure 
               
               
                 3 
                 Gemini 
                 Addition cure 
                 32.7 
                 Reverse 
                 5.5-6.5 
                 1.4 ± 0.2 
                 550 
                 No 
                 1 
               
               
                   
                   
                 RL-26 
                   
                 gravure 
                 5.5-6.5 
                   
                 800 
                 No 
               
               
                 4 
                 Gemini 
                 Addition cure 
                 13.8 
                 Direct 
                 5.5-6.5 
                 3.4 ± 0.5 
                 550 
                 No 
                 3 
               
               
                   
                   
                 RL-26 
                   
                   
                 5.5-6.5 
                   
                 800 
                 Yes 
               
               
                 5 
                 Iris 
                 Condensation 
                 13.8 
                 Direct 
                 5.5-6.5 
                 4.2 
                   
                   
                 2 
               
               
                   
                   
                 Iris 
               
               
                 6 
                 Iris 
                 Addition cure 
                 40.0 
                 Direct 
                 14-17 
                 5.6 
                   
                   
                 3 
               
               
                   
                   
                 RL-26 
               
               
                   
               
            
           
         
       
     
     While the methods, release layers, intermediate transfer members and related aspects have been described with reference to certain examples, those skilled in the art will appreciate that various modifications, changes, omissions, and substitutions can be made without departing from the spirit of the disclosure. It is intended, therefore, that the methods, release layers, intermediate transfer members and related aspects be limited only by the scope of the following claims. Unless otherwise stated, the features of any dependent claim can be combined with the features of any of the other dependent claims, and any other independent claim.