In some substrate coating systems, such as a priming system and/or printing system, a primer is transferred to a substrate before the substrate is printed on. In some printers, sometimes referred to as a press, a substrate coating system is included. In such printers, the primer acts as an undercoat layer to a print layer and improves bonding of the print layer to the substrate. The print layer occurs where the primer is present, such that, areas void of primer corresponding to unprinted areas.
Various features of the present disclosure will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate features of the present disclosure, and wherein:
In the following description, for purposes of explanation, numerous specific details of certain examples are set forth. Reference in the specification to “an example” or similar language means that a particular feature, structure, or characteristic described in connection with the example is included in that one example, but not necessarily in other examples.
In some substrate coating systems, such as a priming system and/or printing system (including digital printing systems and analog printing systems) a method of priming a substrate is performed in a priming process. Some printers can be regarded as a substrate coating system or can comprise a substrate coating system. In some printers, such as a digital printer or press and/or an analog printer or press, the priming process is performed prior to the printing process that comprises printing on the substrate. In some instances, the substrate is referred as a medium or coatable medium. The medium may be referred to as a print medium when the medium is to be passed through a printer because the substrate can receive printing fluid, for example, ink from the printer. The substrate can be a web of material. The substrate may be a film. The priming process involves coating at least a portion of one side of the substrate with a primer, which can be referred to as a coating surface. After the priming process and after the primer has dried, the substrate is printed on in a printing process. The primer is a coating substance and, in most instances, is a fluid. The primer provides a base layer for the printing fluid. The base layer is sometimes referred to as an undercoat. In some instances, such as for in-line printers, a print job includes both the priming process and the printing process. Such in-line printers are therefore printers that combine the application of the primer to the substrate and the subsequent application of the printing fluid. In in-line printers, the substrate is fed continuously between a primer system and a print system.
In a priming system, a primer is transferred to a substrate using a transfer member, such as a transfer roller. The transfer member picks up primer from a storage, such as a chamber, and applies the primer to a surface of the substrate. In most instances, a doctor blade is used to wipe excess primer from the surface of the transfer member to ensure an even exposure of the substrate to primer. When the primer reaches the substrate, the substrate is coated. In instance, when a transfer roller is used to apply prime the substrate, the transfer roller rotates about an axis to transport the primer from the storage and to a substrate surface. One type of transfer roller is an anilox roller, which is described in more detail below. In most instances, a doctor blade is a thin, elongate member that substantially extends along a dimension of the transfer member, such as the length of a transfer roller. The doctor blade is to divert excess primer away from the transfer member. In some instances, an area of a doctor blade is in communication with a storage tank such that excess primer can be removed and possibly reused within the printer.
In an indirect priming mode, the transfer member transfers primer to an intermediate member before the intermediate member transfers the primer to the substrate. In a direct priming mode, the transfer member transfers the primer directly to the substrate without the intermediate member.
Some priming systems directly transfer the primer from the transfer member to the substrate in the direct priming mode. For example, as the transfer roller rotates, primer attached to a surface of the transfer is passed straight to the substrate. In some instances, a “kiss” mode is used to transfer the substrate. A “kiss” mode is an example of a direct priming mode wherein a transfer member or a span of substrate is brought just close enough to the other to transfer primer to the substrate with minimal disturbance to a path of movement of the substrate. The bringing together of the transfer member and substrate, which may result in engagement, is controlled to ensure primer is transferred effectively. In some instances, the transfer member touches the substrate via the primer and without the primer, the transfer member would not contact the substrate. The light contact is enough for the primer to switch from the transfer member to the substrate without pressing the primer to the substrate. When a transfer roller is used, the transfer is made between a tangential surface of the transfer roller and the substrate. A surface speed of the transfer roller may be substantially equal to a speed of traverse of the substrate. However, the surface speed of the transfer roller may be above or below the speed of the substrate. In some instances, the control of the transfer member to engage and/or disengage the substrate is performed manually. In other instances, the engagements and/or disengagement may be by a controller to actuate an electromechanical, pneumatic or hydraulic means.
To transfer the primer to the substrate, a transfer roller may rotate in the same direction as the substrate, such that there is little or no relative movement between the transfer roller and substrate. In other instances, a direction of movement of the transfer roller may be in a direction opposite to the direction of movement of the substrate. When using a “kiss” mode transfer, the process of opposing the motion of the transfer roller and the substrate is referred to as a “reverse kiss” mode.
A gravure roller is a type of transfer roller. Coating a substrate with a gravure roller may be referred to as gravure coating. Gravure coating is a process of producing continuous coatings on a substrate. The gravure roller comprises depressions or recesses on an application surface. The depressions or recesses are to control a thickness and uniformity of a coated layer on the substrate. Fluid, such as primer, is uniformly “picked out” of the depressions or recesses and transferred to the substrate. In most instances, the pattern of depressions or recesses is regular to enable a continuous and uniform coating is applied. The gravure roller is specifically designed to avoid damage to the substrate during the coating process because substrates can be susceptible to scratching.
One example of a gravure roller is an anilox roller. The anilox roller comprises a transfer element containing a precisely manufactured microstructure forming cells to precisely control a volume and distribution of primer to the substrate. The distribution of the transfer element across the anilox roller determines the distribution of primer on the substrate. In most instances, the transfer element is an outer layer of a cylinder that rotates about an axis. The cells are to receive primer and may be engravings. The transfer element may therefore comprise etched, machined, or knurled recesses on its surface which can be any shape or size, discontinuous, or continuous over the roller surface. The volume of these recesses controls the average coating thickness, and the specific geometry can be designed to enhance the stability of a pickout of the primer from the recesses. The ability to accurately control the volume and shape of these recesses together with the stability of the pickout of a regular fraction of the fluid in these recesses improves coating thickness uniformity in the substrate.
As the anilox roller rotates, the primer is deposited on the transfer element and is transferred to a substrate by way of rotation of the anilox roller. The anilox roller provides a desirable metering of the primer onto the substrate. The distribution of the transfer element across the anilox roller determines the distribution of primer on the substrate.
In some instances, an entire width of a substrate is coated by primer. Such a process is referred to as flood coating because the substrate is effectively flooded by primer. Other priming modes include lane coating, which involves coating the substrate with a primer in a lane arrangement. In lane coating, a transfer roller coats portions of the substrate to form lanes of coated and uncoated regions.
When using an anilox roller, the transfer element of the anilox roller is spaced across the anilox roller to provide a plurality of spaced cell regions. The spaced regions allow primer to be transferred to the substrate in lanes. In most instances, the lane pattern is fixed for each anilox roller. To prime a substrate with a different lane pattern, a second anilox roller, with a differently distributed transfer element is needed. The second anilox roller replaces the anilox roller currently installed in the printer and the printing process resumes once the second anilox roller is installed in the printer. Therefore, to change the lane pattern, a different anilox roller is used. An operator disengages the anilox roller from the substrate and removes the anilox roller from the printer. Given that anilox rollers are precisely manufactured, changing the anilox roller is performed carefully by a trained operator. Once the anilox roller is removed, the anilox roller is stored for later use. The anilox roller may be stored with an array of anilox roller that provide an array of lane patterns. To ensure good priming quality, the anilox roller is treated with care. Any damage to the cells of the anilox roller effect priming quality.
The term to lift is not intended to be limited by direction. The term lift may refer to a sideways or downwards direction and not just an upwards direction. The apparatus lifts the substrate 2 to move the substrate 2 away from the transfer member 3 to avoid a coating of the substrate by the transfer member 3. The movement of the substrate 2 is a deflection of the substrate 2 from a transport path. The transport path may comprise an imaginary line drawn tangentially between two rollers. The imaginary line may be in a transfer zone. In most instances, a majority of the substrate 2 follows the imaginary line, except for sections of the substrate 2 that interact with the apparatus 1 and are lifted by the apparatus 1.
The substrate coating system 100 shown in
Digital Offset Color printing, sometimes also referred to as Liquid Electrophotography (LEP), is the process of printing in which liquid toner is applied onto a surface having a pattern of electrostatic charge (i.e. a latent image) to form a pattern of liquid toner corresponding with the electrostatic charge pattern (i.e. a developed image). This pattern of liquid toner is then transferred to at least one intermediate surface, such as a surface of a blanket of an image transfer medium, and then to a print medium. During the operation of a liquid electrophotographic system, developed images are formed on the surface of a PIP. These developed images are transferred to a blanket, that is heatable and may be provided around a cylinder, and then to the substrate.
According to the example of
Furthermore, an adjuster 50 that is arranged to position the guide member 11 relative to the transfer member 30 is shown. The substrate 20 is to be deflected by the guide member 11 based on a position of the guide member 11. The guide member 11 is to therefore guide a portion 22 of a width of the substrate 20 away from the transfer member 30 to avoid transfer of the substance S from the transfer member 30 to the guided portion 22 of the substrate 20. Unguided portions of the substrate 20 are coated by the substance S. The guide member 11 is to guide the substrate 20 by relative movement between the guide member 11 and the substrate 20.
The substrate 20 is coated by the substance S in a transfer zone T. The transfer zone T is a region of the priming system of the printer 101 wherein the transfer member 30 applies the substance S to the substrate 20. Referring to
The guide member 11 shown in the priming system of the printer 101 of
The transfer member 30 and tension rollers 41, 42 may be driven independently. That is, rotation of the transfer member 30 is caused by a different means than rotation of the tension rollers 41, 42. For example, the priming system may comprise a first driving member to drive the transfer member 30 and a second driving member, that is different to the first driving member, to drive the tensions rollers 41, 42. The first driving member may be a motor (not shown). The second driving member may be the substrate 20. In this example, the tension rollers 41, 42 act as idler rollers because the tension rollers 41, 42 are driven by the movement of the substrate 20 across the tension rollers 41, 42.
In the example of
A tension applied by the tension rollers 41, 42 is enough to avoid buckling in a width direction of the substrate 20 and frequency fluctuations in the span of substrate 20.
As shown in
In
The above tests results were obtained from a guide member 11 as shown in
Referring to
The controller may include electromechanical control. The controller may control the relative position of the guide member 11 and the transfer member during a print job. That is, the guide member 11 may move “on-the-fly”. The guide member 11 may move across a width of the substrate 20 to change the lane pattern. The print job includes a priming event. The print job may further include a printing event. When the priming event and printing event is performed as a combination in a print job, the priming event and printing event may be said to be in-line.
The adjuster 50 may be a support member, such as a rail. The support member may provide a range of positions of the guide member 11 across the support member. For example, when the adjuster 50 is a rail, the rail may span a width of the transfer member 30. The guide member 11 may be moveable along the rail, wherein the degree of movement may be discrete or continuous. The controller may move the guide member 11 and/or may hold a position of the guide member 11 relative to the adjuster 50.
The deflector 110 comprises a plurality of members 112. The members are referred to as wipers 112 because the members are slideable across a surface of the substrate 120. In some instances, a single wiper 112 may be used. Each wiper 112 may be referred to as a finger 112 or a lifting finger. The wiper 112 is to provide gliding contact with the substrate 120 so as freely slide across the surface of the substrate and not adhere to the substrate 120.
The deflector 110 of
The base 114 may be coupled to an adjuster such as that shown in
In the example shown in
The wipers 112 of the deflector 110 shown in
In some instances, a plurality of deflectors 110 may be positioned by an adjuster. The plurality of deflectors 110 may be further moveable relative to the adjuster. The degree of movement may be controlled by a controller. The controller may further hold the relative position of the deflector and adjuster. The space between adjacent deflectors 110 may be changed to affect a width of a coated lane on the substrate 120.
Referring to
In some instances, the array of wipers 210, 220, 230 are part of the same deflector. In other instances, at least one of the wipers 210, 220, 230 is part of a first deflector and another one of the at least one of the wipers 210, 220, 230 is part of second deflector. In the latter case, a plurality of deflectors can be used, wherein each deflector comprises at least one wiper.
The transfer zone 200 in
Turning to
As shown in
In the uncoated lane 325, a first portion 325a directly contacts a wiper of a deflector, such as that shown in
Referring to
As shown in
Although, a circular cross-section of a wiper 410, 420, 430, 440 is shown in
As shown in
A spacing or gap G1 between adjacent wiping elements of
In some instances, the distance between each wiper 510, 520, 530, 540 may change for example by a controller. The spacing or gap G1, G2 between each wiping element 521, 522 may also change. Such changes may occur during a print job, which is “on-the-fly”. A lane patterns can be changed quickly using the same anilox roller, for example, when an anilox roller is used as the transfer member.
At block 610, the method 600 comprises moving a print medium along a transport path. The print medium comprises a substrate onto which printing fluid is printed. The substrate may be made of a synthetic material such as a polymeric material. A polymeric material enables good adhesion of the printing fluid to the substrate. The substrate may be paper, PETG (polyethylene terephthalate) or a laminated tube, for example. The print medium may be continuous, for example when the print medium is provided in web form, or discrete, for example when the print medium is provided in sheet form. The print medium may be fed on a per sheet basis, or from a roll sometimes referred to as a web substrate.
At block 620, the method 600 comprises tensioning the print medium in a transfer zone. In some instances, blocks 610 and 620 are interchangeable. In some other instances, the tensioning occurs before the moving and in others, the moving occurs before the tensioning.
At block 630, the method 600 comprises coating a first portion of the print medium in the transfer zone by transferring fluid between a fluid transfer surface and the print medium.
At block 640, the method 600 comprises lifting a second portion of the print medium away from the fluid transfer surface to prevent fluid transfer to the second portion, so that, in the transfer zone, the transport path comprises a section, corresponding to the second portion of the print medium, that is lifted relative to another section, corresponding to the first portion of the print medium.
In some examples, block 640 may comprise block 650. At block 650, the method 600 comprises lifting the second portion using a lifting finger to produce an uncoated lane on the print medium, wherein a width of the uncoated lane is less than or equal to twice a width of the lifting finger. In some examples, the directing the second portion may be with a plurality of lifting fingers or wiping elements such that the plurality of lifting fingers or wiping elements produce the same uncoated lane.
Certain system components and methods described herein may be implemented by way of non-transitory computer program code that is storable on a non-transitory storage medium. In some examples, the controller 260 shown in
The preceding description has been presented to illustrate and describe examples of the principles described. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with any features of any other of the examples, or any combination of any other of the examples.
Filing Document | Filing Date | Country | Kind |
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PCT/US2018/061176 | 11/15/2018 | WO | 00 |